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fuchsia / third_party / rust / 4e40a0d43640a5cf26f28cea35ec16445966a000 / . / src / libsyntax / parse / parser.rs
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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use abi::{self, Abi};
use ast::{AngleBracketedParameterData, ParenthesizedParameterData, AttrStyle, BareFnTy};
use ast::{RegionTyParamBound, TraitTyParamBound, TraitBoundModifier};
use ast::Unsafety;
use ast::{Mod, Arg, Arm, Attribute, BindingMode, TraitItemKind};
use ast::Block;
use ast::{BlockCheckMode, CaptureBy};
use ast::{Constness, Crate};
use ast::Defaultness;
use ast::EnumDef;
use ast::{Expr, ExprKind, RangeLimits};
use ast::{Field, FnDecl};
use ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
use ast::GenericParam;
use ast::{Ident, ImplItem, IsAuto, Item, ItemKind};
use ast::{Lifetime, LifetimeDef, Lit, LitKind, UintTy};
use ast::Local;
use ast::MacStmtStyle;
use ast::Mac_;
use ast::{MutTy, Mutability};
use ast::{Pat, PatKind, PathSegment};
use ast::{PolyTraitRef, QSelf};
use ast::{Stmt, StmtKind};
use ast::{VariantData, StructField};
use ast::StrStyle;
use ast::SelfKind;
use ast::{TraitItem, TraitRef, TraitObjectSyntax};
use ast::{Ty, TyKind, TypeBinding, TyParam, TyParamBounds};
use ast::{Visibility, WhereClause, CrateSugar};
use ast::{UseTree, UseTreeKind};
use ast::{BinOpKind, UnOp};
use ast::{RangeEnd, RangeSyntax};
use {ast, attr};
use codemap::{self, CodeMap, Spanned, respan};
use syntax_pos::{self, Span, BytePos, FileName, DUMMY_SP};
use errors::{self, DiagnosticBuilder};
use parse::{self, classify, token};
use parse::common::SeqSep;
use parse::lexer::TokenAndSpan;
use parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
use parse::obsolete::ObsoleteSyntax;
use parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
use util::parser::{AssocOp, Fixity};
use print::pprust;
use ptr::P;
use parse::PResult;
use tokenstream::{self, Delimited, ThinTokenStream, TokenTree, TokenStream};
use symbol::{Symbol, keywords};
use util::ThinVec;
use std::cmp;
use std::collections::HashSet;
use std::mem;
use std::path::{self, Path, PathBuf};
use std::slice;
bitflags! {
pub struct Restrictions: u8 {
const STMT_EXPR = 1 << 0;
const NO_STRUCT_LITERAL = 1 << 1;
}
}
type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute> >);
/// How to parse a path.
#[derive(Copy, Clone, PartialEq)]
pub enum PathStyle {
/// In some contexts, notably in expressions, paths with generic arguments are ambiguous
/// with something else. For example, in expressions `segment < ....` can be interpreted
/// as a comparison and `segment ( ....` can be interpreted as a function call.
/// In all such contexts the non-path interpretation is preferred by default for practical
/// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
/// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
Expr,
/// In other contexts, notably in types, no ambiguity exists and paths can be written
/// without the disambiguator, e.g. `x<y>` - unambiguously a path.
/// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
Type,
/// A path with generic arguments disallowed, e.g. `foo::bar::Baz`, used in imports,
/// visibilities or attributes.
/// Technically, this variant is unnecessary and e.g. `Expr` can be used instead
/// (paths in "mod" contexts have to be checked later for absence of generic arguments
/// anyway, due to macros), but it is used to avoid weird suggestions about expected
/// tokens when something goes wrong.
Mod,
}
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum SemiColonMode {
Break,
Ignore,
}
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum BlockMode {
Break,
Ignore,
}
/// Possibly accept an `token::Interpolated` expression (a pre-parsed expression
/// dropped into the token stream, which happens while parsing the result of
/// macro expansion). Placement of these is not as complex as I feared it would
/// be. The important thing is to make sure that lookahead doesn't balk at
/// `token::Interpolated` tokens.
macro_rules! maybe_whole_expr {
($p:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
match nt.0 {
token::NtExpr(ref e) => {
$p.bump();
return Ok((*e).clone());
}
token::NtPath(ref path) => {
$p.bump();
let span = $p.span;
let kind = ExprKind::Path(None, (*path).clone());
return Ok($p.mk_expr(span, kind, ThinVec::new()));
}
token::NtBlock(ref block) => {
$p.bump();
let span = $p.span;
let kind = ExprKind::Block((*block).clone());
return Ok($p.mk_expr(span, kind, ThinVec::new()));
}
_ => {},
};
}
}
}
/// As maybe_whole_expr, but for things other than expressions
macro_rules! maybe_whole {
($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
if let token::Interpolated(nt) = $p.token.clone() {
if let token::$constructor($x) = nt.0.clone() {
$p.bump();
return Ok($e);
}
}
};
}
fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
-> Vec<Attribute> {
if let Some(ref attrs) = rhs {
lhs.extend(attrs.iter().cloned())
}
lhs
}
#[derive(Debug, Clone, Copy, PartialEq)]
enum PrevTokenKind {
DocComment,
Comma,
Plus,
Interpolated,
Eof,
Ident,
Other,
}
trait RecoverQPath: Sized {
const PATH_STYLE: PathStyle = PathStyle::Expr;
fn to_ty(&self) -> Option<P<Ty>>;
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
fn to_string(&self) -> String;
}
impl RecoverQPath for Ty {
const PATH_STYLE: PathStyle = PathStyle::Type;
fn to_ty(&self) -> Option<P<Ty>> {
Some(P(self.clone()))
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::ty_to_string(self)
}
}
impl RecoverQPath for Pat {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
}
fn to_string(&self) -> String {
pprust::pat_to_string(self)
}
}
impl RecoverQPath for Expr {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
Self { span: path.span, node: ExprKind::Path(qself, path),
id: self.id, attrs: self.attrs.clone() }
}
fn to_string(&self) -> String {
pprust::expr_to_string(self)
}
}
/* ident is handled by common.rs */
#[derive(Clone)]
pub struct Parser<'a> {
pub sess: &'a ParseSess,
/// the current token:
pub token: token::Token,
/// the span of the current token:
pub span: Span,
/// the span of the previous token:
pub meta_var_span: Option<Span>,
pub prev_span: Span,
/// the previous token kind
prev_token_kind: PrevTokenKind,
pub restrictions: Restrictions,
/// The set of seen errors about obsolete syntax. Used to suppress
/// extra detail when the same error is seen twice
pub obsolete_set: HashSet<ObsoleteSyntax>,
/// Used to determine the path to externally loaded source files
pub directory: Directory,
/// Whether to parse sub-modules in other files.
pub recurse_into_file_modules: bool,
/// Name of the root module this parser originated from. If `None`, then the
/// name is not known. This does not change while the parser is descending
/// into modules, and sub-parsers have new values for this name.
pub root_module_name: Option<String>,
pub expected_tokens: Vec<TokenType>,
token_cursor: TokenCursor,
pub desugar_doc_comments: bool,
/// Whether we should configure out of line modules as we parse.
pub cfg_mods: bool,
}
#[derive(Clone)]
struct TokenCursor {
frame: TokenCursorFrame,
stack: Vec<TokenCursorFrame>,
}
#[derive(Clone)]
struct TokenCursorFrame {
delim: token::DelimToken,
span: Span,
open_delim: bool,
tree_cursor: tokenstream::Cursor,
close_delim: bool,
last_token: LastToken,
}
/// This is used in `TokenCursorFrame` above to track tokens that are consumed
/// by the parser, and then that's transitively used to record the tokens that
/// each parse AST item is created with.
///
/// Right now this has two states, either collecting tokens or not collecting
/// tokens. If we're collecting tokens we just save everything off into a local
/// `Vec`. This should eventually though likely save tokens from the original
/// token stream and just use slicing of token streams to avoid creation of a
/// whole new vector.
///
/// The second state is where we're passively not recording tokens, but the last
/// token is still tracked for when we want to start recording tokens. This
/// "last token" means that when we start recording tokens we'll want to ensure
/// that this, the first token, is included in the output.
///
/// You can find some more example usage of this in the `collect_tokens` method
/// on the parser.
#[derive(Clone)]
enum LastToken {
Collecting(Vec<TokenTree>),
Was(Option<TokenTree>),
}
impl TokenCursorFrame {
fn new(sp: Span, delimited: &Delimited) -> Self {
TokenCursorFrame {
delim: delimited.delim,
span: sp,
open_delim: delimited.delim == token::NoDelim,
tree_cursor: delimited.stream().into_trees(),
close_delim: delimited.delim == token::NoDelim,
last_token: LastToken::Was(None),
}
}
}
impl TokenCursor {
fn next(&mut self) -> TokenAndSpan {
loop {
let tree = if !self.frame.open_delim {
self.frame.open_delim = true;
Delimited { delim: self.frame.delim, tts: TokenStream::empty().into() }
.open_tt(self.frame.span)
} else if let Some(tree) = self.frame.tree_cursor.next() {
tree
} else if !self.frame.close_delim {
self.frame.close_delim = true;
Delimited { delim: self.frame.delim, tts: TokenStream::empty().into() }
.close_tt(self.frame.span)
} else if let Some(frame) = self.stack.pop() {
self.frame = frame;
continue
} else {
return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
};
match self.frame.last_token {
LastToken::Collecting(ref mut v) => v.push(tree.clone()),
LastToken::Was(ref mut t) => *t = Some(tree.clone()),
}
match tree {
TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
TokenTree::Delimited(sp, ref delimited) => {
let frame = TokenCursorFrame::new(sp, delimited);
self.stack.push(mem::replace(&mut self.frame, frame));
}
}
}
}
fn next_desugared(&mut self) -> TokenAndSpan {
let (sp, name) = match self.next() {
TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
tok => return tok,
};
let stripped = strip_doc_comment_decoration(&name.as_str());
// Searches for the occurrences of `"#*` and returns the minimum number of `#`s
// required to wrap the text.
let mut num_of_hashes = 0;
let mut count = 0;
for ch in stripped.chars() {
count = match ch {
'"' => 1,
'#' if count > 0 => count + 1,
_ => 0,
};
num_of_hashes = cmp::max(num_of_hashes, count);
}
let body = TokenTree::Delimited(sp, Delimited {
delim: token::Bracket,
tts: [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"))),
TokenTree::Token(sp, token::Eq),
TokenTree::Token(sp, token::Literal(
token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))]
.iter().cloned().collect::<TokenStream>().into(),
});
self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(sp, &Delimited {
delim: token::NoDelim,
tts: if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
[TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
.iter().cloned().collect::<TokenStream>().into()
} else {
[TokenTree::Token(sp, token::Pound), body]
.iter().cloned().collect::<TokenStream>().into()
},
})));
self.next()
}
}
#[derive(PartialEq, Eq, Clone)]
pub enum TokenType {
Token(token::Token),
Keyword(keywords::Keyword),
Operator,
Lifetime,
Ident,
Path,
Type,
}
impl TokenType {
fn to_string(&self) -> String {
match *self {
TokenType::Token(ref t) => format!("`{}`", Parser::token_to_string(t)),
TokenType::Keyword(kw) => format!("`{}`", kw.name()),
TokenType::Operator => "an operator".to_string(),
TokenType::Lifetime => "lifetime".to_string(),
TokenType::Ident => "identifier".to_string(),
TokenType::Path => "path".to_string(),
TokenType::Type => "type".to_string(),
}
}
}
// Returns true if `IDENT t` can start a type - `IDENT::a::b`, `IDENT<u8, u8>`,
// `IDENT<<u8 as Trait>::AssocTy>`, `IDENT(u8, u8) -> u8`.
fn can_continue_type_after_ident(t: &token::Token) -> bool {
t == &token::ModSep || t == &token::Lt ||
t == &token::BinOp(token::Shl) || t == &token::OpenDelim(token::Paren)
}
/// Information about the path to a module.
pub struct ModulePath {
pub name: String,
pub path_exists: bool,
pub result: Result<ModulePathSuccess, Error>,
}
pub struct ModulePathSuccess {
pub path: PathBuf,
pub directory_ownership: DirectoryOwnership,
warn: bool,
}
pub struct ModulePathError {
pub err_msg: String,
pub help_msg: String,
}
pub enum Error {
FileNotFoundForModule {
mod_name: String,
default_path: String,
secondary_path: String,
dir_path: String,
},
DuplicatePaths {
mod_name: String,
default_path: String,
secondary_path: String,
},
UselessDocComment,
InclusiveRangeWithNoEnd,
}
impl Error {
pub fn span_err(self, sp: Span, handler: &errors::Handler) -> DiagnosticBuilder {
match self {
Error::FileNotFoundForModule { ref mod_name,
ref default_path,
ref secondary_path,
ref dir_path } => {
let mut err = struct_span_err!(handler, sp, E0583,
"file not found for module `{}`", mod_name);
err.help(&format!("name the file either {} or {} inside the directory {:?}",
default_path,
secondary_path,
dir_path));
err
}
Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
let mut err = struct_span_err!(handler, sp, E0584,
"file for module `{}` found at both {} and {}",
mod_name,
default_path,
secondary_path);
err.help("delete or rename one of them to remove the ambiguity");
err
}
Error::UselessDocComment => {
let mut err = struct_span_err!(handler, sp, E0585,
"found a documentation comment that doesn't document anything");
err.help("doc comments must come before what they document, maybe a comment was \
intended with `//`?");
err
}
Error::InclusiveRangeWithNoEnd => {
let mut err = struct_span_err!(handler, sp, E0586,
"inclusive range with no end");
err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
err
}
}
}
}
#[derive(Debug)]
pub enum LhsExpr {
NotYetParsed,
AttributesParsed(ThinVec<Attribute>),
AlreadyParsed(P<Expr>),
}
impl From<Option<ThinVec<Attribute>>> for LhsExpr {
fn from(o: Option<ThinVec<Attribute>>) -> Self {
if let Some(attrs) = o {
LhsExpr::AttributesParsed(attrs)
} else {
LhsExpr::NotYetParsed
}
}
}
impl From<P<Expr>> for LhsExpr {
fn from(expr: P<Expr>) -> Self {
LhsExpr::AlreadyParsed(expr)
}
}
/// Create a placeholder argument.
fn dummy_arg(span: Span) -> Arg {
let spanned = Spanned {
span,
node: keywords::Invalid.ident()
};
let pat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), spanned, None),
span,
});
let ty = Ty {
node: TyKind::Err,
span,
id: ast::DUMMY_NODE_ID
};
Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum TokenExpectType {
Expect,
NoExpect,
}
impl<'a> Parser<'a> {
pub fn new(sess: &'a ParseSess,
tokens: TokenStream,
directory: Option<Directory>,
recurse_into_file_modules: bool,
desugar_doc_comments: bool)
-> Self {
let mut parser = Parser {
sess,
token: token::Underscore,
span: syntax_pos::DUMMY_SP,
prev_span: syntax_pos::DUMMY_SP,
meta_var_span: None,
prev_token_kind: PrevTokenKind::Other,
restrictions: Restrictions::empty(),
obsolete_set: HashSet::new(),
recurse_into_file_modules,
directory: Directory {
path: PathBuf::new(),
ownership: DirectoryOwnership::Owned { relative: None }
},
root_module_name: None,
expected_tokens: Vec::new(),
token_cursor: TokenCursor {
frame: TokenCursorFrame::new(syntax_pos::DUMMY_SP, &Delimited {
delim: token::NoDelim,
tts: tokens.into(),
}),
stack: Vec::new(),
},
desugar_doc_comments,
cfg_mods: true,
};
let tok = parser.next_tok();
parser.token = tok.tok;
parser.span = tok.sp;
if let Some(directory) = directory {
parser.directory = directory;
} else if !parser.span.source_equal(&DUMMY_SP) {
if let FileName::Real(path) = sess.codemap().span_to_unmapped_path(parser.span) {
parser.directory.path = path;
parser.directory.path.pop();
}
}
parser.process_potential_macro_variable();
parser
}
fn next_tok(&mut self) -> TokenAndSpan {
let mut next = if self.desugar_doc_comments {
self.token_cursor.next_desugared()
} else {
self.token_cursor.next()
};
if next.sp == syntax_pos::DUMMY_SP {
next.sp = self.prev_span;
}
next
}
/// Convert a token to a string using self's reader
pub fn token_to_string(token: &token::Token) -> String {
pprust::token_to_string(token)
}
/// Convert the current token to a string using self's reader
pub fn this_token_to_string(&self) -> String {
Parser::token_to_string(&self.token)
}
pub fn token_descr(&self) -> Option<&'static str> {
Some(match &self.token {
t if t.is_special_ident() => "reserved identifier",
t if t.is_used_keyword() => "keyword",
t if t.is_unused_keyword() => "reserved keyword",
_ => return None,
})
}
pub fn this_token_descr(&self) -> String {
if let Some(prefix) = self.token_descr() {
format!("{} `{}`", prefix, self.this_token_to_string())
} else {
format!("`{}`", self.this_token_to_string())
}
}
pub fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
let token_str = Parser::token_to_string(t);
Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
}
pub fn unexpected<T>(&mut self) -> PResult<'a, T> {
match self.expect_one_of(&[], &[]) {
Err(e) => Err(e),
Ok(_) => unreachable!(),
}
}
/// Expect and consume the token t. Signal an error if
/// the next token is not t.
pub fn expect(&mut self, t: &token::Token) -> PResult<'a, ()> {
if self.expected_tokens.is_empty() {
if self.token == *t {
self.bump();
Ok(())
} else {
let token_str = Parser::token_to_string(t);
let this_token_str = self.this_token_to_string();
Err(self.fatal(&format!("expected `{}`, found `{}`",
token_str,
this_token_str)))
}
} else {
self.expect_one_of(unsafe { slice::from_raw_parts(t, 1) }, &[])
}
}
/// Expect next token to be edible or inedible token. If edible,
/// then consume it; if inedible, then return without consuming
/// anything. Signal a fatal error if next token is unexpected.
pub fn expect_one_of(&mut self,
edible: &[token::Token],
inedible: &[token::Token]) -> PResult<'a, ()>{
fn tokens_to_string(tokens: &[TokenType]) -> String {
let mut i = tokens.iter();
// This might be a sign we need a connect method on Iterator.
let b = i.next()
.map_or("".to_string(), |t| t.to_string());
i.enumerate().fold(b, |mut b, (i, a)| {
if tokens.len() > 2 && i == tokens.len() - 2 {
b.push_str(", or ");
} else if tokens.len() == 2 && i == tokens.len() - 2 {
b.push_str(" or ");
} else {
b.push_str(", ");
}
b.push_str(&a.to_string());
b
})
}
if edible.contains(&self.token) {
self.bump();
Ok(())
} else if inedible.contains(&self.token) {
// leave it in the input
Ok(())
} else {
let mut expected = edible.iter()
.map(|x| TokenType::Token(x.clone()))
.chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
.chain(self.expected_tokens.iter().cloned())
.collect::<Vec<_>>();
expected.sort_by(|a, b| a.to_string().cmp(&b.to_string()));
expected.dedup();
let expect = tokens_to_string(&expected[..]);
let actual = self.this_token_to_string();
let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
let short_expect = if expected.len() > 6 {
format!("{} possible tokens", expected.len())
} else {
expect.clone()
};
(format!("expected one of {}, found `{}`", expect, actual),
(self.prev_span.next_point(), format!("expected one of {} here", short_expect)))
} else if expected.is_empty() {
(format!("unexpected token: `{}`", actual),
(self.prev_span, "unexpected token after this".to_string()))
} else {
(format!("expected {}, found `{}`", expect, actual),
(self.prev_span.next_point(), format!("expected {} here", expect)))
};
let mut err = self.fatal(&msg_exp);
let sp = if self.token == token::Token::Eof {
// This is EOF, don't want to point at the following char, but rather the last token
self.prev_span
} else {
label_sp
};
let cm = self.sess.codemap();
match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
(Ok(ref a), Ok(ref b)) if a.line == b.line => {
// When the spans are in the same line, it means that the only content between
// them is whitespace, point at the found token in that case:
//
// X | () => { syntax error };
// | ^^^^^ expected one of 8 possible tokens here
//
// instead of having:
//
// X | () => { syntax error };
// | -^^^^^ unexpected token
// | |
// | expected one of 8 possible tokens here
err.span_label(self.span, label_exp);
}
_ => {
err.span_label(sp, label_exp);
err.span_label(self.span, "unexpected token");
}
}
Err(err)
}
}
/// returns the span of expr, if it was not interpolated or the span of the interpolated token
fn interpolated_or_expr_span(&self,
expr: PResult<'a, P<Expr>>)
-> PResult<'a, (Span, P<Expr>)> {
expr.map(|e| {
if self.prev_token_kind == PrevTokenKind::Interpolated {
(self.prev_span, e)
} else {
(e.span, e)
}
})
}
pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
self.parse_ident_common(true)
}
fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(i) => {
if self.token.is_reserved_ident() {
let mut err = self.struct_span_err(self.span,
&format!("expected identifier, found {}",
self.this_token_descr()));
if let Some(token_descr) = self.token_descr() {
err.span_label(self.span, format!("expected identifier, found {}",
token_descr));
} else {
err.span_label(self.span, "expected identifier");
}
if recover {
err.emit();
} else {
return Err(err);
}
}
self.bump();
Ok(i)
}
_ => {
Err(if self.prev_token_kind == PrevTokenKind::DocComment {
self.span_fatal_err(self.prev_span, Error::UselessDocComment)
} else {
let mut err = self.fatal(&format!("expected identifier, found `{}`",
self.this_token_to_string()));
if let Some(token_descr) = self.token_descr() {
err.span_label(self.span, format!("expected identifier, found {}",
token_descr));
} else {
err.span_label(self.span, "expected identifier");
}
if self.token == token::Underscore {
err.note("`_` is a wildcard pattern, not an identifier");
}
err
})
}
}
}
/// Check if the next token is `tok`, and return `true` if so.
///
/// This method will automatically add `tok` to `expected_tokens` if `tok` is not
/// encountered.
pub fn check(&mut self, tok: &token::Token) -> bool {
let is_present = self.token == *tok;
if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
is_present
}
/// Consume token 'tok' if it exists. Returns true if the given
/// token was present, false otherwise.
pub fn eat(&mut self, tok: &token::Token) -> bool {
let is_present = self.check(tok);
if is_present { self.bump() }
is_present
}
pub fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
self.expected_tokens.push(TokenType::Keyword(kw));
self.token.is_keyword(kw)
}
/// If the next token is the given keyword, eat it and return
/// true. Otherwise, return false.
pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
if self.check_keyword(kw) {
self.bump();
true
} else {
false
}
}
pub fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
if self.token.is_keyword(kw) {
self.bump();
true
} else {
false
}
}
/// If the given word is not a keyword, signal an error.
/// If the next token is not the given word, signal an error.
/// Otherwise, eat it.
pub fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
if !self.eat_keyword(kw) {
self.unexpected()
} else {
Ok(())
}
}
fn check_ident(&mut self) -> bool {
if self.token.is_ident() {
true
} else {
self.expected_tokens.push(TokenType::Ident);
false
}
}
fn check_path(&mut self) -> bool {
if self.token.is_path_start() {
true
} else {
self.expected_tokens.push(TokenType::Path);
false
}
}
fn check_type(&mut self) -> bool {
if self.token.can_begin_type() {
true
} else {
self.expected_tokens.push(TokenType::Type);
false
}
}
/// Expect and consume an `&`. If `&&` is seen, replace it with a single
/// `&` and continue. If an `&` is not seen, signal an error.
fn expect_and(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
match self.token {
token::BinOp(token::And) => {
self.bump();
Ok(())
}
token::AndAnd => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::And), span))
}
_ => self.unexpected()
}
}
/// Expect and consume an `|`. If `||` is seen, replace it with a single
/// `|` and continue. If an `|` is not seen, signal an error.
fn expect_or(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
match self.token {
token::BinOp(token::Or) => {
self.bump();
Ok(())
}
token::OrOr => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::Or), span))
}
_ => self.unexpected()
}
}
pub fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
match suffix {
None => {/* everything ok */}
Some(suf) => {
let text = suf.as_str();
if text.is_empty() {
self.span_bug(sp, "found empty literal suffix in Some")
}
self.span_err(sp, &format!("{} with a suffix is invalid", kind));
}
}
}
/// Attempt to consume a `<`. If `<<` is seen, replace it with a single
/// `<` and continue. If a `<` is not seen, return false.
///
/// This is meant to be used when parsing generics on a path to get the
/// starting token.
fn eat_lt(&mut self) -> bool {
self.expected_tokens.push(TokenType::Token(token::Lt));
match self.token {
token::Lt => {
self.bump();
true
}
token::BinOp(token::Shl) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
self.bump_with(token::Lt, span);
true
}
_ => false,
}
}
fn expect_lt(&mut self) -> PResult<'a, ()> {
if !self.eat_lt() {
self.unexpected()
} else {
Ok(())
}
}
/// Expect and consume a GT. if a >> is seen, replace it
/// with a single > and continue. If a GT is not seen,
/// signal an error.
pub fn expect_gt(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::Gt));
match self.token {
token::Gt => {
self.bump();
Ok(())
}
token::BinOp(token::Shr) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::Gt, span))
}
token::BinOpEq(token::Shr) => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::Ge, span))
}
token::Ge => {
let span = self.span.with_lo(self.span.lo() + BytePos(1));
Ok(self.bump_with(token::Eq, span))
}
_ => self.unexpected()
}
}
pub fn parse_seq_to_before_gt_or_return<T, F>(&mut self,
sep: Option<token::Token>,
mut f: F)
-> PResult<'a, (Vec<T>, bool)>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, Option<T>>,
{
let mut v = Vec::new();
// This loop works by alternating back and forth between parsing types
// and commas. For example, given a string `A, B,>`, the parser would
// first parse `A`, then a comma, then `B`, then a comma. After that it
// would encounter a `>` and stop. This lets the parser handle trailing
// commas in generic parameters, because it can stop either after
// parsing a type or after parsing a comma.
for i in 0.. {
if self.check(&token::Gt)
|| self.token == token::BinOp(token::Shr)
|| self.token == token::Ge
|| self.token == token::BinOpEq(token::Shr) {
break;
}
if i % 2 == 0 {
match f(self)? {
Some(result) => v.push(result),
None => return Ok((v, true))
}
} else {
if let Some(t) = sep.as_ref() {
self.expect(t)?;
}
}
}
return Ok((v, false));
}
/// Parse a sequence bracketed by '<' and '>', stopping
/// before the '>'.
pub fn parse_seq_to_before_gt<T, F>(&mut self,
sep: Option<token::Token>,
mut f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let (result, returned) = self.parse_seq_to_before_gt_or_return(sep,
|p| Ok(Some(f(p)?)))?;
assert!(!returned);
return Ok(result);
}
pub fn parse_seq_to_gt<T, F>(&mut self,
sep: Option<token::Token>,
f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let v = self.parse_seq_to_before_gt(sep, f)?;
self.expect_gt()?;
return Ok(v);
}
pub fn parse_seq_to_gt_or_return<T, F>(&mut self,
sep: Option<token::Token>,
f: F)
-> PResult<'a, (Vec<T>, bool)> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, Option<T>>,
{
let (v, returned) = self.parse_seq_to_before_gt_or_return(sep, f)?;
if !returned {
self.expect_gt()?;
}
return Ok((v, returned));
}
/// Eat and discard tokens until one of `kets` is encountered. Respects token trees,
/// passes through any errors encountered. Used for error recovery.
pub fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
let handler = self.diagnostic();
if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
SeqSep::none(),
TokenExpectType::Expect,
|p| Ok(p.parse_token_tree())) {
handler.cancel(err);
}
}
/// Parse a sequence, including the closing delimiter. The function
/// f must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_end<T, F>(&mut self,
ket: &token::Token,
sep: SeqSep,
f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let val = self.parse_seq_to_before_end(ket, sep, f)?;
self.bump();
Ok(val)
}
/// Parse a sequence, not including the closing delimiter. The function
/// f must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_before_end<T, F>(&mut self,
ket: &token::Token,
sep: SeqSep,
f: F)
-> PResult<'a, Vec<T>>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
}
fn parse_seq_to_before_tokens<T, F>(&mut self,
kets: &[&token::Token],
sep: SeqSep,
expect: TokenExpectType,
mut f: F)
-> PResult<'a, Vec<T>>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
let mut first: bool = true;
let mut v = vec![];
while !kets.contains(&&self.token) {
match self.token {
token::CloseDelim(..) | token::Eof => break,
_ => {}
};
if let Some(ref t) = sep.sep {
if first {
first = false;
} else {
if let Err(mut e) = self.expect(t) {
// Attempt to keep parsing if it was a similar separator
if let Some(ref tokens) = t.similar_tokens() {
if tokens.contains(&self.token) {
self.bump();
}
}
e.emit();
// Attempt to keep parsing if it was an omitted separator
match f(self) {
Ok(t) => {
v.push(t);
continue;
},
Err(mut e) => {
e.cancel();
break;
}
}
}
}
}
if sep.trailing_sep_allowed && kets.iter().any(|k| {
match expect {
TokenExpectType::Expect => self.check(k),
TokenExpectType::NoExpect => self.token == **k,
}
}) {
break;
}
let t = f(self)?;
v.push(t);
}
Ok(v)
}
/// Parse a sequence, including the closing delimiter. The function
/// f must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_unspanned_seq<T, F>(&mut self,
bra: &token::Token,
ket: &token::Token,
sep: SeqSep,
f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
self.expect(bra)?;
let result = self.parse_seq_to_before_end(ket, sep, f)?;
if self.token == *ket {
self.bump();
}
Ok(result)
}
// NB: Do not use this function unless you actually plan to place the
// spanned list in the AST.
pub fn parse_seq<T, F>(&mut self,
bra: &token::Token,
ket: &token::Token,
sep: SeqSep,
f: F)
-> PResult<'a, Spanned<Vec<T>>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let lo = self.span;
self.expect(bra)?;
let result = self.parse_seq_to_before_end(ket, sep, f)?;
let hi = self.span;
self.bump();
Ok(respan(lo.to(hi), result))
}
/// Advance the parser by one token
pub fn bump(&mut self) {
if self.prev_token_kind == PrevTokenKind::Eof {
// Bumping after EOF is a bad sign, usually an infinite loop.
self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
}
self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
// Record last token kind for possible error recovery.
self.prev_token_kind = match self.token {
token::DocComment(..) => PrevTokenKind::DocComment,
token::Comma => PrevTokenKind::Comma,
token::BinOp(token::Plus) => PrevTokenKind::Plus,
token::Interpolated(..) => PrevTokenKind::Interpolated,
token::Eof => PrevTokenKind::Eof,
token::Ident(..) => PrevTokenKind::Ident,
_ => PrevTokenKind::Other,
};
let next = self.next_tok();
self.span = next.sp;
self.token = next.tok;
self.expected_tokens.clear();
// check after each token
self.process_potential_macro_variable();
}
/// Advance the parser using provided token as a next one. Use this when
/// consuming a part of a token. For example a single `<` from `<<`.
pub fn bump_with(&mut self, next: token::Token, span: Span) {
self.prev_span = self.span.with_hi(span.lo());
// It would be incorrect to record the kind of the current token, but
// fortunately for tokens currently using `bump_with`, the
// prev_token_kind will be of no use anyway.
self.prev_token_kind = PrevTokenKind::Other;
self.span = span;
self.token = next;
self.expected_tokens.clear();
}
pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
F: FnOnce(&token::Token) -> R,
{
if dist == 0 {
return f(&self.token)
}
f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
Some(tree) => match tree {
TokenTree::Token(_, tok) => tok,
TokenTree::Delimited(_, delimited) => token::OpenDelim(delimited.delim),
},
None => token::CloseDelim(self.token_cursor.frame.delim),
})
}
fn look_ahead_span(&self, dist: usize) -> Span {
if dist == 0 {
return self.span
}
match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
Some(TokenTree::Token(span, _)) | Some(TokenTree::Delimited(span, _)) => span,
None => self.look_ahead_span(dist - 1),
}
}
pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_fatal(self.span, m)
}
pub fn span_fatal(&self, sp: Span, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_fatal(sp, m)
}
pub fn span_fatal_err(&self, sp: Span, err: Error) -> DiagnosticBuilder<'a> {
err.span_err(sp, self.diagnostic())
}
pub fn span_fatal_help(&self, sp: Span, m: &str, help: &str) -> DiagnosticBuilder<'a> {
let mut err = self.sess.span_diagnostic.struct_span_fatal(sp, m);
err.help(help);
err
}
pub fn bug(&self, m: &str) -> ! {
self.sess.span_diagnostic.span_bug(self.span, m)
}
pub fn warn(&self, m: &str) {
self.sess.span_diagnostic.span_warn(self.span, m)
}
pub fn span_warn(&self, sp: Span, m: &str) {
self.sess.span_diagnostic.span_warn(sp, m)
}
pub fn span_err(&self, sp: Span, m: &str) {
self.sess.span_diagnostic.span_err(sp, m)
}
pub fn struct_span_err(&self, sp: Span, m: &str) -> DiagnosticBuilder<'a> {
self.sess.span_diagnostic.struct_span_err(sp, m)
}
pub fn span_err_help(&self, sp: Span, m: &str, h: &str) {
let mut err = self.sess.span_diagnostic.mut_span_err(sp, m);
err.help(h);
err.emit();
}
pub fn span_bug(&self, sp: Span, m: &str) -> ! {
self.sess.span_diagnostic.span_bug(sp, m)
}
pub fn abort_if_errors(&self) {
self.sess.span_diagnostic.abort_if_errors();
}
fn cancel(&self, err: &mut DiagnosticBuilder) {
self.sess.span_diagnostic.cancel(err)
}
pub fn diagnostic(&self) -> &'a errors::Handler {
&self.sess.span_diagnostic
}
/// Is the current token one of the keywords that signals a bare function
/// type?
pub fn token_is_bare_fn_keyword(&mut self) -> bool {
self.check_keyword(keywords::Fn) ||
self.check_keyword(keywords::Unsafe) ||
self.check_keyword(keywords::Extern)
}
fn get_label(&mut self) -> ast::Ident {
match self.token {
token::Lifetime(ref ident) => *ident,
token::Interpolated(ref nt) => match nt.0 {
token::NtLifetime(lifetime) => lifetime.ident,
_ => self.bug("not a lifetime"),
},
_ => self.bug("not a lifetime"),
}
}
/// parse a TyKind::BareFn type:
pub fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>)
-> PResult<'a, TyKind> {
/*
[unsafe] [extern "ABI"] fn (S) -> T
^~~~^ ^~~~^ ^~^ ^
| | | |
| | | Return type
| | Argument types
| |
| ABI
Function Style
*/
let unsafety = self.parse_unsafety()?;
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(keywords::Fn)?;
let (inputs, variadic) = self.parse_fn_args(false, true)?;
let ret_ty = self.parse_ret_ty()?;
let decl = P(FnDecl {
inputs,
output: ret_ty,
variadic,
});
Ok(TyKind::BareFn(P(BareFnTy {
abi,
unsafety,
generic_params,
decl,
})))
}
pub fn parse_unsafety(&mut self) -> PResult<'a, Unsafety> {
if self.eat_keyword(keywords::Unsafe) {
return Ok(Unsafety::Unsafe);
} else {
return Ok(Unsafety::Normal);
}
}
/// Parse the items in a trait declaration
pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
maybe_whole!(self, NtTraitItem, |x| x);
let attrs = self.parse_outer_attributes()?;
let (mut item, tokens) = self.collect_tokens(|this| {
this.parse_trait_item_(at_end, attrs)
})?;
// See `parse_item` for why this clause is here.
if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
item.tokens = Some(tokens);
}
Ok(item)
}
fn parse_trait_item_(&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
let lo = self.span;
let (name, node, generics) = if self.eat_keyword(keywords::Type) {
let (generics, TyParam {ident, bounds, default, ..}) =
self.parse_trait_item_assoc_ty(vec![])?;
(ident, TraitItemKind::Type(bounds, default), generics)
} else if self.is_const_item() {
self.expect_keyword(keywords::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let default = if self.check(&token::Eq) {
self.bump();
let expr = self.parse_expr()?;
self.expect(&token::Semi)?;
Some(expr)
} else {
self.expect(&token::Semi)?;
None
};
(ident, TraitItemKind::Const(ty, default), ast::Generics::default())
} else if self.token.is_path_start() && !self.is_extern_non_path() {
// trait item macro.
// code copied from parse_macro_use_or_failure... abstraction!
let prev_span = self.prev_span;
let lo = self.span;
let pth = self.parse_path(PathStyle::Mod)?;
if pth.segments.len() == 1 {
if !self.eat(&token::Not) {
return Err(self.missing_assoc_item_kind_err("trait", prev_span));
}
} else {
self.expect(&token::Not)?;
}
// eat a matched-delimiter token tree:
let (delim, tts) = self.expect_delimited_token_tree()?;
if delim != token::Brace {
self.expect(&token::Semi)?
}
let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
(keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
} else {
let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>|{
// This is somewhat dubious; We don't want to allow
// argument names to be left off if there is a
// definition...
p.parse_arg_general(false)
})?;
generics.where_clause = self.parse_where_clause()?;
let sig = ast::MethodSig {
unsafety,
constness,
decl: d,
abi,
};
let body = match self.token {
token::Semi => {
self.bump();
*at_end = true;
debug!("parse_trait_methods(): parsing required method");
None
}
token::OpenDelim(token::Brace) => {
debug!("parse_trait_methods(): parsing provided method");
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
_ => {
let token_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected `;` or `{{`, found `{}`", token_str)));
}
};
(ident, ast::TraitItemKind::Method(sig, body), generics)
};
Ok(TraitItem {
id: ast::DUMMY_NODE_ID,
ident: name,
attrs,
generics,
node,
span: lo.to(self.prev_span),
tokens: None,
})
}
/// Parse optional return type [ -> TY ] in function decl
pub fn parse_ret_ty(&mut self) -> PResult<'a, FunctionRetTy> {
if self.eat(&token::RArrow) {
Ok(FunctionRetTy::Ty(self.parse_ty_no_plus()?))
} else {
Ok(FunctionRetTy::Default(self.span.with_hi(self.span.lo())))
}
}
// Parse a type
pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(true, true)
}
/// Parse a type in restricted contexts where `+` is not permitted.
/// Example 1: `&'a TYPE`
/// `+` is prohibited to maintain operator priority (P(+) < P(&)).
/// Example 2: `value1 as TYPE + value2`
/// `+` is prohibited to avoid interactions with expression grammar.
fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(false, true)
}
fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool)
-> PResult<'a, P<Ty>> {
maybe_whole!(self, NtTy, |x| x);
let lo = self.span;
let node = if self.eat(&token::OpenDelim(token::Paren)) {
// `(TYPE)` is a parenthesized type.
// `(TYPE,)` is a tuple with a single field of type TYPE.
let mut ts = vec![];
let mut last_comma = false;
while self.token != token::CloseDelim(token::Paren) {
ts.push(self.parse_ty()?);
if self.eat(&token::Comma) {
last_comma = true;
} else {
last_comma = false;
break;
}
}
let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
self.expect(&token::CloseDelim(token::Paren))?;
if ts.len() == 1 && !last_comma {
let ty = ts.into_iter().nth(0).unwrap().into_inner();
let maybe_bounds = allow_plus && self.token == token::BinOp(token::Plus);
match ty.node {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
}
TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
let path = match bounds[0] {
TraitTyParamBound(ref pt, ..) => pt.trait_ref.path.clone(),
_ => self.bug("unexpected lifetime bound"),
};
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
TyKind::Tup(ts)
}
} else if self.eat(&token::Not) {
// Never type `!`
TyKind::Never
} else if self.eat(&token::BinOp(token::Star)) {
// Raw pointer
TyKind::Ptr(self.parse_ptr()?)
} else if self.eat(&token::OpenDelim(token::Bracket)) {
// Array or slice
let t = self.parse_ty()?;
// Parse optional `; EXPR` in `[TYPE; EXPR]`
let t = match self.maybe_parse_fixed_length_of_vec()? {
None => TyKind::Slice(t),
Some(suffix) => TyKind::Array(t, suffix),
};
self.expect(&token::CloseDelim(token::Bracket))?;
t
} else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
// Reference
self.expect_and()?;
self.parse_borrowed_pointee()?
} else if self.eat_keyword_noexpect(keywords::Typeof) {
// `typeof(EXPR)`
// In order to not be ambiguous, the type must be surrounded by parens.
self.expect(&token::OpenDelim(token::Paren))?;
let e = self.parse_expr()?;
self.expect(&token::CloseDelim(token::Paren))?;
TyKind::Typeof(e)
} else if self.eat(&token::Underscore) {
// A type to be inferred `_`
TyKind::Infer
} else if self.token_is_bare_fn_keyword() {
// Function pointer type
self.parse_ty_bare_fn(Vec::new())?
} else if self.check_keyword(keywords::For) {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
if self.token_is_bare_fn_keyword() {
self.parse_ty_bare_fn(lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus && self.check(&token::BinOp(token::Plus));
self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
}
} else if self.eat_keyword(keywords::Impl) {
// FIXME: figure out priority of `+` in `impl Trait1 + Trait2` (#34511).
TyKind::ImplTrait(self.parse_ty_param_bounds()?)
} else if self.check_keyword(keywords::Dyn) &&
self.look_ahead(1, |t| t.can_begin_bound() && !can_continue_type_after_ident(t)) {
// FIXME: figure out priority of `+` in `dyn Trait1 + Trait2` (#34511).
self.bump(); // `dyn`
TyKind::TraitObject(self.parse_ty_param_bounds()?, TraitObjectSyntax::Dyn)
} else if self.check(&token::Question) ||
self.check_lifetime() && self.look_ahead(1, |t| t == &token::BinOp(token::Plus)) {
// Bound list (trait object type)
TyKind::TraitObject(self.parse_ty_param_bounds_common(allow_plus)?,
TraitObjectSyntax::None)
} else if self.eat_lt() {
// Qualified path
let (qself, path) = self.parse_qpath(PathStyle::Type)?;
TyKind::Path(Some(qself), path)
} else if self.token.is_path_start() {
// Simple path
let path = self.parse_path(PathStyle::Type)?;
if self.eat(&token::Not) {
// Macro invocation in type position
let (_, tts) = self.expect_delimited_token_tree()?;
TyKind::Mac(respan(lo.to(self.prev_span), Mac_ { path: path, tts: tts }))
} else {
// Just a type path or bound list (trait object type) starting with a trait.
// `Type`
// `Trait1 + Trait2 + 'a`
if allow_plus && self.check(&token::BinOp(token::Plus)) {
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
} else {
TyKind::Path(None, path)
}
}
} else {
let msg = format!("expected type, found {}", self.this_token_descr());
return Err(self.fatal(&msg));
};
let span = lo.to(self.prev_span);
let ty = Ty { node, span, id: ast::DUMMY_NODE_ID };
// Try to recover from use of `+` with incorrect priority.
self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;
Ok(P(ty))
}
fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
let mut bounds = vec![TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None)];
if parse_plus {
self.bump(); // `+`
bounds.append(&mut self.parse_ty_param_bounds()?);
}
Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
}
fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
// Do not add `+` to expected tokens.
if !allow_plus || self.token != token::BinOp(token::Plus) {
return Ok(())
}
self.bump(); // `+`
let bounds = self.parse_ty_param_bounds()?;
let sum_span = ty.span.to(self.prev_span);
let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
"expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
match ty.node {
TyKind::Rptr(ref lifetime, ref mut_ty) => {
let sum_with_parens = pprust::to_string(|s| {
use print::pprust::PrintState;
s.s.word("&")?;
s.print_opt_lifetime(lifetime)?;
s.print_mutability(mut_ty.mutbl)?;
s.popen()?;
s.print_type(&mut_ty.ty)?;
s.print_bounds(" +", &bounds)?;
s.pclose()
});
err.span_suggestion(sum_span, "try adding parentheses", sum_with_parens);
}
TyKind::Ptr(..) | TyKind::BareFn(..) => {
err.span_label(sum_span, "perhaps you forgot parentheses?");
}
_ => {
err.span_label(sum_span, "expected a path");
},
}
err.emit();
Ok(())
}
// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
-> PResult<'a, T> {
// Do not add `::` to expected tokens.
if !allow_recovery || self.token != token::ModSep {
return Ok(base);
}
let ty = match base.to_ty() {
Some(ty) => ty,
None => return Ok(base),
};
self.bump(); // `::`
let mut segments = Vec::new();
self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
let span = ty.span.to(self.prev_span);
let recovered =
base.to_recovered(Some(QSelf { ty, position: 0 }), ast::Path { segments, span });
self.diagnostic()
.struct_span_err(span, "missing angle brackets in associated item path")
.span_suggestion(span, "try", recovered.to_string()).emit();
Ok(recovered)
}
fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
let mutbl = self.parse_mutability();
let ty = self.parse_ty_no_plus()?;
return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
}
pub fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
let mutbl = if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else if self.eat_keyword(keywords::Const) {
Mutability::Immutable
} else {
let span = self.prev_span;
self.span_err(span,
"expected mut or const in raw pointer type (use \
`*mut T` or `*const T` as appropriate)");
Mutability::Immutable
};
let t = self.parse_ty_no_plus()?;
Ok(MutTy { ty: t, mutbl: mutbl })
}
fn is_named_argument(&mut self) -> bool {
let offset = match self.token {
token::Interpolated(ref nt) => match nt.0 {
token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
_ => 0,
}
token::BinOp(token::And) | token::AndAnd => 1,
_ if self.token.is_keyword(keywords::Mut) => 1,
_ => 0,
};
self.look_ahead(offset, |t| t.is_ident() || t == &token::Underscore) &&
self.look_ahead(offset + 1, |t| t == &token::Colon)
}
/// This version of parse arg doesn't necessarily require
/// identifier names.
pub fn parse_arg_general(&mut self, require_name: bool) -> PResult<'a, Arg> {
maybe_whole!(self, NtArg, |x| x);
let pat = if require_name || self.is_named_argument() {
debug!("parse_arg_general parse_pat (require_name:{})",
require_name);
let pat = self.parse_pat()?;
self.expect(&token::Colon)?;
pat
} else {
debug!("parse_arg_general ident_to_pat");
let sp = self.prev_span;
let spanned = Spanned { span: sp, node: keywords::Invalid.ident() };
P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable),
spanned, None),
span: sp
})
};
let t = self.parse_ty()?;
Ok(Arg {
ty: t,
pat,
id: ast::DUMMY_NODE_ID,
})
}
/// Parse a single function argument
pub fn parse_arg(&mut self) -> PResult<'a, Arg> {
self.parse_arg_general(true)
}
/// Parse an argument in a lambda header e.g. |arg, arg|
pub fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
let pat = self.parse_pat()?;
let t = if self.eat(&token::Colon) {
self.parse_ty()?
} else {
P(Ty {
id: ast::DUMMY_NODE_ID,
node: TyKind::Infer,
span: self.span,
})
};
Ok(Arg {
ty: t,
pat,
id: ast::DUMMY_NODE_ID
})
}
pub fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
if self.eat(&token::Semi) {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
/// Matches token_lit = LIT_INTEGER | ...
pub fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
let out = match self.token {
token::Interpolated(ref nt) => match nt.0 {
token::NtExpr(ref v) => match v.node {
ExprKind::Lit(ref lit) => { lit.node.clone() }
_ => { return self.unexpected_last(&self.token); }
},
_ => { return self.unexpected_last(&self.token); }
},
token::Literal(lit, suf) => {
let diag = Some((self.span, &self.sess.span_diagnostic));
let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
if suffix_illegal {
let sp = self.span;
self.expect_no_suffix(sp, &format!("{} literal", lit.short_name()), suf)
}
result.unwrap()
}
_ => { return self.unexpected_last(&self.token); }
};
self.bump();
Ok(out)
}
/// Matches lit = true | false | token_lit
pub fn parse_lit(&mut self) -> PResult<'a, Lit> {
let lo = self.span;
let lit = if self.eat_keyword(keywords::True) {
LitKind::Bool(true)
} else if self.eat_keyword(keywords::False) {
LitKind::Bool(false)
} else {
let lit = self.parse_lit_token()?;
lit
};
Ok(codemap::Spanned { node: lit, span: lo.to(self.prev_span) })
}
/// matches '-' lit | lit (cf. ast_validation::AstValidator::check_expr_within_pat)
pub fn parse_pat_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
maybe_whole_expr!(self);
let minus_lo = self.span;
let minus_present = self.eat(&token::BinOp(token::Minus));
let lo = self.span;
let literal = P(self.parse_lit()?);
let hi = self.prev_span;
let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
if minus_present {
let minus_hi = self.prev_span;
let unary = self.mk_unary(UnOp::Neg, expr);
Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
} else {
Ok(expr)
}
}
pub fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(sid) if self.token.is_path_segment_keyword() => {
self.bump();
Ok(sid)
}
_ => self.parse_ident(),
}
}
/// Parses qualified path.
/// Assumes that the leading `<` has been parsed already.
///
/// `qualified_path = <type [as trait_ref]>::path`
///
/// # Examples
/// `<T as U>::a`
/// `<T as U>::F::a<S>` (without disambiguator)
/// `<T as U>::F::a::<S>` (with disambiguator)
fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
let lo = self.prev_span;
let ty = self.parse_ty()?;
let mut path = if self.eat_keyword(keywords::As) {
self.parse_path(PathStyle::Type)?
} else {
ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP }
};
self.expect(&token::Gt)?;
self.expect(&token::ModSep)?;
let qself = QSelf { ty, position: path.segments.len() };
self.parse_path_segments(&mut path.segments, style, true)?;
Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
}
/// Parses simple paths.
///
/// `path = [::] segment+`
/// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
///
/// # Examples
/// `a::b::C<D>` (without disambiguator)
/// `a::b::C::<D>` (with disambiguator)
/// `Fn(Args)` (without disambiguator)
/// `Fn::(Args)` (with disambiguator)
pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
self.parse_path_common(style, true)
}
pub fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool)
-> PResult<'a, ast::Path> {
maybe_whole!(self, NtPath, |path| {
if style == PathStyle::Mod &&
path.segments.iter().any(|segment| segment.parameters.is_some()) {
self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
}
path
});
let lo = self.meta_var_span.unwrap_or(self.span);
let mut segments = Vec::new();
if self.eat(&token::ModSep) {
segments.push(PathSegment::crate_root(lo));
}
self.parse_path_segments(&mut segments, style, enable_warning)?;
Ok(ast::Path { segments, span: lo.to(self.prev_span) })
}
/// Like `parse_path`, but also supports parsing `Word` meta items into paths for back-compat.
/// This is used when parsing derive macro paths in `#[derive]` attributes.
pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
let meta_ident = match self.token {
token::Interpolated(ref nt) => match nt.0 {
token::NtMeta(ref meta) => match meta.node {
ast::MetaItemKind::Word => Some(ast::Ident::with_empty_ctxt(meta.name)),
_ => None,
},
_ => None,
},
_ => None,
};
if let Some(ident) = meta_ident {
self.bump();
return Ok(ast::Path::from_ident(self.prev_span, ident));
}
self.parse_path(style)
}
fn parse_path_segments(&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle,
enable_warning: bool)
-> PResult<'a, ()> {
loop {
segments.push(self.parse_path_segment(style, enable_warning)?);
if self.is_import_coupler(false) || !self.eat(&token::ModSep) {
return Ok(());
}
}
}
fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool)
-> PResult<'a, PathSegment> {
let ident_span = self.span;
let ident = self.parse_path_segment_ident()?;
let is_args_start = |token: &token::Token| match *token {
token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
_ => false,
};
let check_args_start = |this: &mut Self| {
this.expected_tokens.extend_from_slice(
&[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
);
is_args_start(&this.token)
};
Ok(if style == PathStyle::Type && check_args_start(self) ||
style != PathStyle::Mod && self.check(&token::ModSep)
&& self.look_ahead(1, |t| is_args_start(t)) {
// Generic arguments are found - `<`, `(`, `::<` or `::(`.
let lo = self.span;
if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
.span_label(self.prev_span, "try removing `::`").emit();
}
let parameters = if self.eat_lt() {
// `<'a, T, A = U>`
let (lifetimes, types, bindings) = self.parse_generic_args()?;
self.expect_gt()?;
let span = lo.to(self.prev_span);
AngleBracketedParameterData { lifetimes, types, bindings, span }.into()
} else {
// `(T, U) -> R`
self.bump(); // `(`
let inputs = self.parse_seq_to_before_tokens(
&[&token::CloseDelim(token::Paren)],
SeqSep::trailing_allowed(token::Comma),
TokenExpectType::Expect,
|p| p.parse_ty())?;
self.bump(); // `)`
let output = if self.eat(&token::RArrow) {
Some(self.parse_ty_common(false, false)?)
} else {
None
};
let span = lo.to(self.prev_span);
ParenthesizedParameterData { inputs, output, span }.into()
};
PathSegment { identifier: ident, span: ident_span, parameters }
} else {
// Generic arguments are not found.
PathSegment::from_ident(ident, ident_span)
})
}
fn check_lifetime(&mut self) -> bool {
self.expected_tokens.push(TokenType::Lifetime);
self.token.is_lifetime()
}
/// Parse single lifetime 'a or panic.
pub fn expect_lifetime(&mut self) -> Lifetime {
if let Some(lifetime) = self.token.lifetime(self.span) {
self.bump();
lifetime
} else {
self.span_bug(self.span, "not a lifetime")
}
}
/// Parse mutability (`mut` or nothing).
fn parse_mutability(&mut self) -> Mutability {
if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else {
Mutability::Immutable
}
}
pub fn parse_field_name(&mut self) -> PResult<'a, Ident> {
if let token::Literal(token::Integer(name), None) = self.token {
self.bump();
Ok(Ident::with_empty_ctxt(name))
} else {
self.parse_ident_common(false)
}
}
/// Parse ident (COLON expr)?
pub fn parse_field(&mut self) -> PResult<'a, Field> {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let hi;
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
let fieldname = self.parse_field_name()?;
self.bump();
hi = self.prev_span;
(fieldname, self.parse_expr()?, false)
} else {
let fieldname = self.parse_ident_common(false)?;
hi = self.prev_span;
// Mimic `x: x` for the `x` field shorthand.
let path = ast::Path::from_ident(lo.to(hi), fieldname);
(fieldname, self.mk_expr(lo.to(hi), ExprKind::Path(None, path), ThinVec::new()), true)
};
Ok(ast::Field {
ident: respan(lo.to(hi), fieldname),
span: lo.to(expr.span),
expr,
is_shorthand,
attrs: attrs.into(),
})
}
pub fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
}
pub fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
ExprKind::Unary(unop, expr)
}
pub fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::Binary(binop, lhs, rhs)
}
pub fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
ExprKind::Call(f, args)
}
pub fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
ExprKind::Index(expr, idx)
}
pub fn mk_range(&mut self,
start: Option<P<Expr>>,
end: Option<P<Expr>>,
limits: RangeLimits)
-> PResult<'a, ast::ExprKind> {
if end.is_none() && limits == RangeLimits::Closed {
Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
} else {
Ok(ExprKind::Range(start, end, limits))
}
}
pub fn mk_tup_field(&mut self, expr: P<Expr>, idx: codemap::Spanned<usize>) -> ast::ExprKind {
ExprKind::TupField(expr, idx)
}
pub fn mk_assign_op(&mut self, binop: ast::BinOp,
lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::AssignOp(binop, lhs, rhs)
}
pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr {
id: ast::DUMMY_NODE_ID,
node: ExprKind::Mac(codemap::Spanned {node: m, span: span}),
span,
attrs,
})
}
pub fn mk_lit_u32(&mut self, i: u32, attrs: ThinVec<Attribute>) -> P<Expr> {
let span = &self.span;
let lv_lit = P(codemap::Spanned {
node: LitKind::Int(i as u128, ast::LitIntType::Unsigned(UintTy::U32)),
span: *span
});
P(Expr {
id: ast::DUMMY_NODE_ID,
node: ExprKind::Lit(lv_lit),
span: *span,
attrs,
})
}
fn expect_delimited_token_tree(&mut self) -> PResult<'a, (token::DelimToken, ThinTokenStream)> {
match self.token {
token::OpenDelim(delim) => match self.parse_token_tree() {
TokenTree::Delimited(_, delimited) => Ok((delim, delimited.stream().into())),
_ => unreachable!(),
},
_ => Err(self.fatal("expected open delimiter")),
}
}
/// At the bottom (top?) of the precedence hierarchy,
/// parse things like parenthesized exprs,
/// macros, return, etc.
///
/// NB: This does not parse outer attributes,
/// and is private because it only works
/// correctly if called from parse_dot_or_call_expr().
fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
maybe_whole_expr!(self);
// Outer attributes are already parsed and will be
// added to the return value after the fact.
//
// Therefore, prevent sub-parser from parsing
// attributes by giving them a empty "already parsed" list.
let mut attrs = ThinVec::new();
let lo = self.span;
let mut hi = self.span;
let ex: ExprKind;
// Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
match self.token {
token::OpenDelim(token::Paren) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
// (e) is parenthesized e
// (e,) is a tuple with only one field, e
let mut es = vec![];
let mut trailing_comma = false;
while self.token != token::CloseDelim(token::Paren) {
es.push(self.parse_expr()?);
self.expect_one_of(&[], &[token::Comma, token::CloseDelim(token::Paren)])?;
if self.check(&token::Comma) {
trailing_comma = true;
self.bump();
} else {
trailing_comma = false;
break;
}
}
self.bump();
hi = self.prev_span;
ex = if es.len() == 1 && !trailing_comma {
ExprKind::Paren(es.into_iter().nth(0).unwrap())
} else {
ExprKind::Tup(es)
};
}
token::OpenDelim(token::Brace) => {
return self.parse_block_expr(lo, BlockCheckMode::Default, attrs);
}
token::BinOp(token::Or) | token::OrOr => {
let lo = self.span;
return self.parse_lambda_expr(lo, CaptureBy::Ref, attrs);
}
token::OpenDelim(token::Bracket) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
if self.check(&token::CloseDelim(token::Bracket)) {
// Empty vector.
self.bump();
ex = ExprKind::Array(Vec::new());
} else {
// Nonempty vector.
let first_expr = self.parse_expr()?;
if self.check(&token::Semi) {
// Repeating array syntax: [ 0; 512 ]
self.bump();
let count = self.parse_expr()?;
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Repeat(first_expr, count);
} else if self.check(&token::Comma) {
// Vector with two or more elements.
self.bump();
let remaining_exprs = self.parse_seq_to_end(
&token::CloseDelim(token::Bracket),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
let mut exprs = vec![first_expr];
exprs.extend(remaining_exprs);
ex = ExprKind::Array(exprs);
} else {
// Vector with one element.
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Array(vec![first_expr]);
}
}
hi = self.prev_span;
}
_ => {
if self.eat_lt() {
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
hi = path.span;
return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
}
if self.eat_keyword(keywords::Move) {
let lo = self.prev_span;
return self.parse_lambda_expr(lo, CaptureBy::Value, attrs);
}
if self.eat_keyword(keywords::If) {
return self.parse_if_expr(attrs);
}
if self.eat_keyword(keywords::For) {
let lo = self.prev_span;
return self.parse_for_expr(None, lo, attrs);
}
if self.eat_keyword(keywords::While) {
let lo = self.prev_span;
return self.parse_while_expr(None, lo, attrs);
}
if self.token.is_lifetime() {
let label = Spanned { node: self.get_label(),
span: self.span };
let lo = self.span;
self.bump();
self.expect(&token::Colon)?;
if self.eat_keyword(keywords::While) {
return self.parse_while_expr(Some(label), lo, attrs)
}
if self.eat_keyword(keywords::For) {
return self.parse_for_expr(Some(label), lo, attrs)
}
if self.eat_keyword(keywords::Loop) {
return self.parse_loop_expr(Some(label), lo, attrs)
}
return Err(self.fatal("expected `while`, `for`, or `loop` after a label"))
}
if self.eat_keyword(keywords::Loop) {
let lo = self.prev_span;
return self.parse_loop_expr(None, lo, attrs);
}
if self.eat_keyword(keywords::Continue) {
let ex = if self.token.is_lifetime() {
let ex = ExprKind::Continue(Some(Spanned{
node: self.get_label(),
span: self.span
}));
self.bump();
ex
} else {
ExprKind::Continue(None)
};
let hi = self.prev_span;
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
if self.eat_keyword(keywords::Match) {
return self.parse_match_expr(attrs);
}
if self.eat_keyword(keywords::Unsafe) {
return self.parse_block_expr(
lo,
BlockCheckMode::Unsafe(ast::UserProvided),
attrs);
}
if self.is_catch_expr() {
let lo = self.span;
assert!(self.eat_keyword(keywords::Do));
assert!(self.eat_keyword(keywords::Catch));
return self.parse_catch_expr(lo, attrs);
}
if self.eat_keyword(keywords::Return) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Ret(Some(e));
} else {
ex = ExprKind::Ret(None);
}
} else if self.eat_keyword(keywords::Break) {
let lt = if self.token.is_lifetime() {
let spanned_lt = Spanned {
node: self.get_label(),
span: self.span
};
self.bump();
Some(spanned_lt)
} else {
None
};
let e = if self.token.can_begin_expr()
&& !(self.token == token::OpenDelim(token::Brace)
&& self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL)) {
Some(self.parse_expr()?)
} else {
None
};
ex = ExprKind::Break(lt, e);
hi = self.prev_span;
} else if self.eat_keyword(keywords::Yield) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Yield(Some(e));
} else {
ex = ExprKind::Yield(None);
}
} else if self.token.is_keyword(keywords::Let) {
// Catch this syntax error here, instead of in `parse_ident`, so
// that we can explicitly mention that let is not to be used as an expression
let mut db = self.fatal("expected expression, found statement (`let`)");
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if self.token.is_path_start() {
let pth = self.parse_path(PathStyle::Expr)?;
// `!`, as an operator, is prefix, so we know this isn't that
if self.eat(&token::Not) {
// MACRO INVOCATION expression
let (_, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
return Ok(self.mk_mac_expr(lo.to(hi), Mac_ { path: pth, tts: tts }, attrs));
}
if self.check(&token::OpenDelim(token::Brace)) {
// This is a struct literal, unless we're prohibited
// from parsing struct literals here.
let prohibited = self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL
);
if !prohibited {
return self.parse_struct_expr(lo, pth, attrs);
}
}
hi = pth.span;
ex = ExprKind::Path(None, pth);
} else {
match self.parse_lit() {
Ok(lit) => {
hi = lit.span;
ex = ExprKind::Lit(P(lit));
}
Err(mut err) => {
self.cancel(&mut err);
let msg = format!("expected expression, found {}",
self.this_token_descr());
return Err(self.fatal(&msg));
}
}
}
}
}
let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
let expr = self.maybe_recover_from_bad_qpath(expr, true)?;
return Ok(P(expr));
}
fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let struct_sp = lo.to(self.prev_span);
self.bump();
let mut fields = Vec::new();
let mut base = None;
attrs.extend(self.parse_inner_attributes()?);
while self.token != token::CloseDelim(token::Brace) {
if self.eat(&token::DotDot) {
let exp_span = self.prev_span;
match self.parse_expr() {
Ok(e) => {
base = Some(e);
}
Err(mut e) => {
e.emit();
self.recover_stmt();
}
}
if self.token == token::Comma {
let mut err = self.sess.span_diagnostic.mut_span_err(
exp_span.to(self.prev_span),
"cannot use a comma after the base struct",
);
err.span_suggestion_short(self.span, "remove this comma", "".to_owned());
err.note("the base struct must always be the last field");
err.emit();
self.recover_stmt();
}
break;
}
match self.parse_field() {
Ok(f) => fields.push(f),
Err(mut e) => {
e.span_label(struct_sp, "while parsing this struct");
e.emit();
self.recover_stmt();
break;
}
}
match self.expect_one_of(&[token::Comma],
&[token::CloseDelim(token::Brace)]) {
Ok(()) => {}
Err(mut e) => {
e.emit();
self.recover_stmt();
break;
}
}
}
let span = lo.to(self.span);
self.expect(&token::CloseDelim(token::Brace))?;
return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
}
fn parse_or_use_outer_attributes(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, ThinVec<Attribute>> {
if let Some(attrs) = already_parsed_attrs {
Ok(attrs)
} else {
self.parse_outer_attributes().map(|a| a.into())
}
}
/// Parse a block or unsafe block
pub fn parse_block_expr(&mut self, lo: Span, blk_mode: BlockCheckMode,
outer_attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
self.expect(&token::OpenDelim(token::Brace))?;
let mut attrs = outer_attrs;
attrs.extend(self.parse_inner_attributes()?);
let blk = self.parse_block_tail(lo, blk_mode)?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk), attrs));
}
/// parse a.b or a(13) or a[4] or just a
pub fn parse_dot_or_call_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let b = self.parse_bottom_expr();
let (span, b) = self.interpolated_or_expr_span(b)?;
self.parse_dot_or_call_expr_with(b, span, attrs)
}
pub fn parse_dot_or_call_expr_with(&mut self,
e0: P<Expr>,
lo: Span,
mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
// Stitch the list of outer attributes onto the return value.
// A little bit ugly, but the best way given the current code
// structure
self.parse_dot_or_call_expr_with_(e0, lo)
.map(|expr|
expr.map(|mut expr| {
attrs.extend::<Vec<_>>(expr.attrs.into());
expr.attrs = attrs;
match expr.node {
ExprKind::If(..) | ExprKind::IfLet(..) => {
if !expr.attrs.is_empty() {
// Just point to the first attribute in there...
let span = expr.attrs[0].span;
self.span_err(span,
"attributes are not yet allowed on `if` \
expressions");
}
}
_ => {}
}
expr
})
)
}
// Assuming we have just parsed `.`, continue parsing into an expression.
fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
let segment = self.parse_path_segment(PathStyle::Expr, true)?;
Ok(match self.token {
token::OpenDelim(token::Paren) => {
// Method call `expr.f()`
let mut args = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
args.insert(0, self_arg);
let span = lo.to(self.prev_span);
self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
}
_ => {
// Field access `expr.f`
if let Some(parameters) = segment.parameters {
self.span_err(parameters.span(),
"field expressions may not have generic arguments");
}
let span = lo.to(self.prev_span);
let ident = respan(segment.span, segment.identifier);
self.mk_expr(span, ExprKind::Field(self_arg, ident), ThinVec::new())
}
})
}
fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
let mut e = e0;
let mut hi;
loop {
// expr?
while self.eat(&token::Question) {
let hi = self.prev_span;
e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
}
// expr.f
if self.eat(&token::Dot) {
match self.token {
token::Ident(..) => {
e = self.parse_dot_suffix(e, lo)?;
}
token::Literal(token::Integer(index_ident), suf) => {
let sp = self.span;
// A tuple index may not have a suffix
self.expect_no_suffix(sp, "tuple index", suf);
let dot_span = self.prev_span;
hi = self.span;
self.bump();
let invalid_msg = "invalid tuple or struct index";
let index = index_ident.as_str().parse::<usize>().ok();
match index {
Some(n) => {
if n.to_string() != index_ident.as_str() {
let mut err = self.struct_span_err(self.prev_span, invalid_msg);
err.span_suggestion(self.prev_span,
"try simplifying the index",
n.to_string());
err.emit();
}
let id = respan(dot_span.to(hi), n);
let field = self.mk_tup_field(e, id);
e = self.mk_expr(lo.to(hi), field, ThinVec::new());
}
None => {
let prev_span = self.prev_span;
self.span_err(prev_span, invalid_msg);
}
}
}
token::Literal(token::Float(n), _suf) => {
self.bump();
let fstr = n.as_str();
let mut err = self.diagnostic().struct_span_err(self.prev_span,
&format!("unexpected token: `{}`", n));
err.span_label(self.prev_span, "unexpected token");
if fstr.chars().all(|x| "0123456789.".contains(x)) {
let float = match fstr.parse::<f64>().ok() {
Some(f) => f,
None => continue,
};
let sugg = pprust::to_string(|s| {
use print::pprust::PrintState;
s.popen()?;
s.print_expr(&e)?;
s.s.word( ".")?;
s.print_usize(float.trunc() as usize)?;
s.pclose()?;
s.s.word(".")?;
s.s.word(fstr.splitn(2, ".").last().unwrap())
});
err.span_suggestion(
lo.to(self.prev_span),
"try parenthesizing the first index",
sugg);
}
return Err(err);
}
_ => {
// FIXME Could factor this out into non_fatal_unexpected or something.
let actual = self.this_token_to_string();
self.span_err(self.span, &format!("unexpected token: `{}`", actual));
}
}
continue;
}
if self.expr_is_complete(&e) { break; }
match self.token {
// expr(...)
token::OpenDelim(token::Paren) => {
let es = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
hi = self.prev_span;
let nd = self.mk_call(e, es);
e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
}
// expr[...]
// Could be either an index expression or a slicing expression.
token::OpenDelim(token::Bracket) => {
self.bump();
let ix = self.parse_expr()?;
hi = self.span;
self.expect(&token::CloseDelim(token::Bracket))?;
let index = self.mk_index(e, ix);
e = self.mk_expr(lo.to(hi), index, ThinVec::new())
}
_ => return Ok(e)
}
}
return Ok(e);
}
pub fn process_potential_macro_variable(&mut self) {
let ident = match self.token {
token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
self.look_ahead(1, |t| t.is_ident()) => {
self.bump();
let name = match self.token { token::Ident(ident) => ident, _ => unreachable!() };
self.fatal(&format!("unknown macro variable `{}`", name)).emit();
return
}
token::Interpolated(ref nt) => {
self.meta_var_span = Some(self.span);
match nt.0 {
token::NtIdent(ident) => ident,
_ => return,
}
}
_ => return,
};
self.token = token::Ident(ident.node);
self.span = ident.span;
}
/// parse a single token tree from the input.
pub fn parse_token_tree(&mut self) -> TokenTree {
match self.token {
token::OpenDelim(..) => {
let frame = mem::replace(&mut self.token_cursor.frame,
self.token_cursor.stack.pop().unwrap());
self.span = frame.span;
self.bump();
TokenTree::Delimited(frame.span, Delimited {
delim: frame.delim,
tts: frame.tree_cursor.original_stream().into(),
})
},
token::CloseDelim(_) | token::Eof => unreachable!(),
_ => {
let (token, span) = (mem::replace(&mut self.token, token::Underscore), self.span);
self.bump();
TokenTree::Token(span, token)
}
}
}
// parse a stream of tokens into a list of TokenTree's,
// up to EOF.
pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
let mut tts = Vec::new();
while self.token != token::Eof {
tts.push(self.parse_token_tree());
}
Ok(tts)
}
pub fn parse_tokens(&mut self) -> TokenStream {
let mut result = Vec::new();
loop {
match self.token {
token::Eof | token::CloseDelim(..) => break,
_ => result.push(self.parse_token_tree().into()),
}
}
TokenStream::concat(result)
}
/// Parse a prefix-unary-operator expr
pub fn parse_prefix_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.span;
// Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
let (hi, ex) = match self.token {
token::Not => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
// Suggest `!` for bitwise negation when encountering a `~`
token::Tilde => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
let span_of_tilde = lo;
let mut err = self.diagnostic().struct_span_err(span_of_tilde,
"`~` can not be used as a unary operator");
err.span_label(span_of_tilde, "did you mean `!`?");
err.help("use `!` instead of `~` if you meant to perform bitwise negation");
err.emit();
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
token::BinOp(token::Minus) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Neg, e))
}
token::BinOp(token::Star) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Deref, e))
}
token::BinOp(token::And) | token::AndAnd => {
self.expect_and()?;
let m = self.parse_mutability();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::AddrOf(m, e))
}
token::Ident(..) if self.token.is_keyword(keywords::In) => {
self.bump();
let place = self.parse_expr_res(
Restrictions::NO_STRUCT_LITERAL,
None,
)?;
let blk = self.parse_block()?;
let span = blk.span;
let blk_expr = self.mk_expr(span, ExprKind::Block(blk), ThinVec::new());
(lo.to(span), ExprKind::InPlace(place, blk_expr))
}
token::Ident(..) if self.token.is_keyword(keywords::Box) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::Box(e))
}
_ => return self.parse_dot_or_call_expr(Some(attrs))
};
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
/// Parse an associative expression
///
/// This parses an expression accounting for associativity and precedence of the operators in
/// the expression.
pub fn parse_assoc_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
self.parse_assoc_expr_with(0, already_parsed_attrs.into())
}
/// Parse an associative expression with operators of at least `min_prec` precedence
pub fn parse_assoc_expr_with(&mut self,
min_prec: usize,
lhs: LhsExpr)
-> PResult<'a, P<Expr>> {
let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
expr
} else {
let attrs = match lhs {
LhsExpr::AttributesParsed(attrs) => Some(attrs),
_ => None,
};
if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
return self.parse_prefix_range_expr(attrs);
} else {
self.parse_prefix_expr(attrs)?
}
};
if self.expr_is_complete(&lhs) {
// Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
return Ok(lhs);
}
self.expected_tokens.push(TokenType::Operator);
while let Some(op) = AssocOp::from_token(&self.token) {
// Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
// it refers to. Interpolated identifiers are unwrapped early and never show up here
// as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
// it as "interpolated", it doesn't change the answer for non-interpolated idents.
let lhs_span = match (self.prev_token_kind, &lhs.node) {
(PrevTokenKind::Interpolated, _) => self.prev_span,
(PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
if path.segments.len() == 1 => self.prev_span,
_ => lhs.span,
};
let cur_op_span = self.span;
let restrictions = if op.is_assign_like() {
self.restrictions & Restrictions::NO_STRUCT_LITERAL
} else {
self.restrictions
};
if op.precedence() < min_prec {
break;
}
// Check for deprecated `...` syntax
if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
self.err_dotdotdot_syntax(self.span);
}
self.bump();
if op.is_comparison() {
self.check_no_chained_comparison(&lhs, &op);
}
// Special cases:
if op == AssocOp::As {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
continue
} else if op == AssocOp::Colon {
lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
Ok(lhs) => lhs,
Err(mut err) => {
err.span_label(self.span,
"expecting a type here because of type ascription");
let cm = self.sess.codemap();
let cur_pos = cm.lookup_char_pos(self.span.lo());
let op_pos = cm.lookup_char_pos(cur_op_span.hi());
if cur_pos.line != op_pos.line {
err.span_suggestion_short(cur_op_span,
"did you mean to use `;` here?",
";".to_string());
}
return Err(err);
}
};
continue
} else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
// If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
// generalise it to the Fixity::None code.
//
// We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
// two variants are handled with `parse_prefix_range_expr` call above.
let rhs = if self.is_at_start_of_range_notation_rhs() {
Some(self.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)?)
} else {
None
};
let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
x.span
} else {
cur_op_span
});
let limits = if op == AssocOp::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = try!(self.mk_range(Some(lhs), rhs, limits));
lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
break
}
let rhs = match op.fixity() {
Fixity::Right => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence(),
LhsExpr::NotYetParsed)
}),
Fixity::Left => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)
}),
// We currently have no non-associative operators that are not handled above by
// the special cases. The code is here only for future convenience.
Fixity::None => self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| {
this.parse_assoc_expr_with(op.precedence() + 1,
LhsExpr::NotYetParsed)
}),
}?;
let span = lhs_span.to(rhs.span);
lhs = match op {
AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
AssocOp::Greater | AssocOp::GreaterEqual => {
let ast_op = op.to_ast_binop().unwrap();
let binary = self.mk_binary(codemap::respan(cur_op_span, ast_op), lhs, rhs);
self.mk_expr(span, binary, ThinVec::new())
}
AssocOp::Assign =>
self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
AssocOp::Inplace =>
self.mk_expr(span, ExprKind::InPlace(lhs, rhs), ThinVec::new()),
AssocOp::AssignOp(k) => {
let aop = match k {
token::Plus => BinOpKind::Add,
token::Minus => BinOpKind::Sub,
token::Star => BinOpKind::Mul,
token::Slash => BinOpKind::Div,
token::Percent => BinOpKind::Rem,
token::Caret => BinOpKind::BitXor,
token::And => BinOpKind::BitAnd,
token::Or => BinOpKind::BitOr,
token::Shl => BinOpKind::Shl,
token::Shr => BinOpKind::Shr,
};
let aopexpr = self.mk_assign_op(codemap::respan(cur_op_span, aop), lhs, rhs);
self.mk_expr(span, aopexpr, ThinVec::new())
}
AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
self.bug("AssocOp should have been handled by special case")
}
};
if op.fixity() == Fixity::None { break }
}
Ok(lhs)
}
fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
-> PResult<'a, P<Expr>> {
let mk_expr = |this: &mut Self, rhs: P<Ty>| {
this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
};
// Save the state of the parser before parsing type normally, in case there is a
// LessThan comparison after this cast.
let parser_snapshot_before_type = self.clone();
match self.parse_ty_no_plus() {
Ok(rhs) => {
Ok(mk_expr(self, rhs))
}
Err(mut type_err) => {
// Rewind to before attempting to parse the type with generics, to recover
// from situations like `x as usize < y` in which we first tried to parse
// `usize < y` as a type with generic arguments.
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
match self.parse_path(PathStyle::Expr) {
Ok(path) => {
let (op_noun, op_verb) = match self.token {
token::Lt => ("comparison", "comparing"),
token::BinOp(token::Shl) => ("shift", "shifting"),
_ => {
// We can end up here even without `<` being the next token, for
// example because `parse_ty_no_plus` returns `Err` on keywords,
// but `parse_path` returns `Ok` on them due to error recovery.
// Return original error and parser state.
mem::replace(self, parser_snapshot_after_type);
return Err(type_err);
}
};
// Successfully parsed the type path leaving a `<` yet to parse.
type_err.cancel();
// Report non-fatal diagnostics, keep `x as usize` as an expression
// in AST and continue parsing.
let msg = format!("`<` is interpreted as a start of generic \
arguments for `{}`, not a {}", path, op_noun);
let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
"interpreted as generic arguments");
err.span_label(self.span, format!("not interpreted as {}", op_noun));
let expr = mk_expr(self, P(Ty {
span: path.span,
node: TyKind::Path(None, path),
id: ast::DUMMY_NODE_ID
}));
let expr_str = self.sess.codemap().span_to_snippet(expr.span)
.unwrap_or(pprust::expr_to_string(&expr));
err.span_suggestion(expr.span,
&format!("try {} the casted value", op_verb),
format!("({})", expr_str));
err.emit();
Ok(expr)
}
Err(mut path_err) => {
// Couldn't parse as a path, return original error and parser state.
path_err.cancel();
mem::replace(self, parser_snapshot_after_type);
Err(type_err)
}
}
}
}
}
/// Produce an error if comparison operators are chained (RFC #558).
/// We only need to check lhs, not rhs, because all comparison ops
/// have same precedence and are left-associative
fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
debug_assert!(outer_op.is_comparison(),
"check_no_chained_comparison: {:?} is not comparison",
outer_op);
match lhs.node {
ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
// respan to include both operators
let op_span = op.span.to(self.span);
let mut err = self.diagnostic().struct_span_err(op_span,
"chained comparison operators require parentheses");
if op.node == BinOpKind::Lt &&
*outer_op == AssocOp::Less || // Include `<` to provide this recommendation
*outer_op == AssocOp::Greater // even in a case like the following:
{ // Foo<Bar<Baz<Qux, ()>>>
err.help(
"use `::<...>` instead of `<...>` if you meant to specify type arguments");
err.help("or use `(...)` if you meant to specify fn arguments");
}
err.emit();
}
_ => {}
}
}
/// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
fn parse_prefix_range_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
// Check for deprecated `...` syntax
if self.token == token::DotDotDot {
self.err_dotdotdot_syntax(self.span);
}
debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
"parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
self.token);
let tok = self.token.clone();
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.span;
let mut hi = self.span;
self.bump();
let opt_end = if self.is_at_start_of_range_notation_rhs() {
// RHS must be parsed with more associativity than the dots.
let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
Some(self.parse_assoc_expr_with(next_prec,
LhsExpr::NotYetParsed)
.map(|x|{
hi = x.span;
x
})?)
} else {
None
};
let limits = if tok == token::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = try!(self.mk_range(None,
opt_end,
limits));
Ok(self.mk_expr(lo.to(hi), r, attrs))
}
fn is_at_start_of_range_notation_rhs(&self) -> bool {
if self.token.can_begin_expr() {
// parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
if self.token == token::OpenDelim(token::Brace) {
return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
}
true
} else {
false
}
}
/// Parse an 'if' or 'if let' expression ('if' token already eaten)
pub fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.check_keyword(keywords::Let) {
return self.parse_if_let_expr(attrs);
}
let lo = self.prev_span;
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
// Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
// verify that the last statement is either an implicit return (no `;`) or an explicit
// return. This won't catch blocks with an explicit `return`, but that would be caught by
// the dead code lint.
if self.eat_keyword(keywords::Else) || !cond.returns() {
let sp = lo.next_point();
let mut err = self.diagnostic()
.struct_span_err(sp, "missing condition for `if` statemement");
err.span_label(sp, "expected if condition here");
return Err(err)
}
let thn = self.parse_block()?;
let mut els: Option<P<Expr>> = None;
let mut hi = thn.span;
if self.eat_keyword(keywords::Else) {
let elexpr = self.parse_else_expr()?;
hi = elexpr.span;
els = Some(elexpr);
}
Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
}
/// Parse an 'if let' expression ('if' token already eaten)
pub fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let lo = self.prev_span;
self.expect_keyword(keywords::Let)?;
let pat = self.parse_pat()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let thn = self.parse_block()?;
let (hi, els) = if self.eat_keyword(keywords::Else) {
let expr = self.parse_else_expr()?;
(expr.span, Some(expr))
} else {
(thn.span, None)
};
Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pat, expr, thn, els), attrs))
}
// `move |args| expr`
pub fn parse_lambda_expr(&mut self,
lo: Span,
capture_clause: CaptureBy,
attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let decl = self.parse_fn_block_decl()?;
let decl_hi = self.prev_span;
let body = match decl.output {
FunctionRetTy::Default(_) => {
let restrictions = self.restrictions - Restrictions::STMT_EXPR;
self.parse_expr_res(restrictions, None)?
},
_ => {
// If an explicit return type is given, require a
// block to appear (RFC 968).
let body_lo = self.span;
self.parse_block_expr(body_lo, BlockCheckMode::Default, ThinVec::new())?
}
};
Ok(self.mk_expr(
lo.to(body.span),
ExprKind::Closure(capture_clause, decl, body, lo.to(decl_hi)),
attrs))
}
// `else` token already eaten
pub fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
if self.eat_keyword(keywords::If) {
return self.parse_if_expr(ThinVec::new());
} else {
let blk = self.parse_block()?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk), ThinVec::new()));
}
}
/// Parse a 'for' .. 'in' expression ('for' token already eaten)
pub fn parse_for_expr(&mut self, opt_ident: Option<ast::SpannedIdent>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
// Parse: `for <src_pat> in <src_expr> <src_loop_block>`
let pat = self.parse_pat()?;
if !self.eat_keyword(keywords::In) {
let in_span = self.prev_span.between(self.span);
let mut err = self.sess.span_diagnostic
.struct_span_err(in_span, "missing `in` in `for` loop");
err.span_suggestion_short(in_span, "try adding `in` here", " in ".into());
err.emit();
}
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let hi = self.prev_span;
Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_ident), attrs))
}
/// Parse a 'while' or 'while let' expression ('while' token already eaten)
pub fn parse_while_expr(&mut self, opt_ident: Option<ast::SpannedIdent>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.token.is_keyword(keywords::Let) {
return self.parse_while_let_expr(opt_ident, span_lo, attrs);
}
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_ident), attrs));
}
/// Parse a 'while let' expression ('while' token already eaten)
pub fn parse_while_let_expr(&mut self, opt_ident: Option<ast::SpannedIdent>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
self.expect_keyword(keywords::Let)?;
let pat = self.parse_pat()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::WhileLet(pat, expr, body, opt_ident), attrs));
}
// parse `loop {...}`, `loop` token already eaten
pub fn parse_loop_expr(&mut self, opt_ident: Option<ast::SpannedIdent>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
Ok(self.mk_expr(span, ExprKind::Loop(body, opt_ident), attrs))
}
/// Parse a `do catch {...}` expression (`do catch` token already eaten)
pub fn parse_catch_expr(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
Ok(self.mk_expr(span_lo.to(body.span), ExprKind::Catch(body), attrs))
}
// `match` token already eaten
fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let match_span = self.prev_span;
let lo = self.prev_span;
let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
None)?;
if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
if self.token == token::Token::Semi {
e.span_note(match_span, "did you mean to remove this `match` keyword?");
}
return Err(e)
}
attrs.extend(self.parse_inner_attributes()?);
let mut arms: Vec<Arm> = Vec::new();
while self.token != token::CloseDelim(token::Brace) {
match self.parse_arm() {
Ok(arm) => arms.push(arm),
Err(mut e) => {
// Recover by skipping to the end of the block.
e.emit();
self.recover_stmt();
let span = lo.to(self.span);
if self.token == token::CloseDelim(token::Brace) {
self.bump();
}
return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
}
}
}
let hi = self.span;
self.bump();
return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
}
pub fn parse_arm(&mut self) -> PResult<'a, Arm> {
maybe_whole!(self, NtArm, |x| x);
let attrs = self.parse_outer_attributes()?;
// Allow a '|' before the pats (RFC 1925)
let beginning_vert = if self.eat(&token::BinOp(token::Or)) {
Some(self.prev_span)
} else {
None
};
let pats = self.parse_pats()?;
let guard = if self.eat_keyword(keywords::If) {
Some(self.parse_expr()?)
} else {
None
};
self.expect(&token::FatArrow)?;
let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)?;
let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
&& self.token != token::CloseDelim(token::Brace);
if require_comma {
self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])?;
} else {
self.eat(&token::Comma);
}
Ok(ast::Arm {
attrs,
pats,
guard,
body: expr,
beginning_vert,
})
}
/// Parse an expression
pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
self.parse_expr_res(Restrictions::empty(), None)
}
/// Evaluate the closure with restrictions in place.
///
/// After the closure is evaluated, restrictions are reset.
pub fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
where F: FnOnce(&mut Self) -> T
{
let old = self.restrictions;
self.restrictions = r;
let r = f(self);
self.restrictions = old;
return r;
}
/// Parse an expression, subject to the given restrictions
pub fn parse_expr_res(&mut self, r: Restrictions,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
}
/// Parse the RHS of a local variable declaration (e.g. '= 14;')
fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
if self.check(&token::Eq) {
self.bump();
Ok(Some(self.parse_expr()?))
} else if skip_eq {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
/// Parse patterns, separated by '|' s
fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
let mut pats = Vec::new();
loop {
pats.push(self.parse_pat()?);
if self.token == token::OrOr {
let mut err = self.struct_span_err(self.span,
"unexpected token `||` after pattern");
err.span_suggestion(self.span,
"use a single `|` to specify multiple patterns",
"|".to_owned());
err.emit();
self.bump();
} else if self.check(&token::BinOp(token::Or)) {
self.bump();
} else {
return Ok(pats);
}
};
}
fn parse_pat_tuple_elements(&mut self, unary_needs_comma: bool)
-> PResult<'a, (Vec<P<Pat>>, Option<usize>)> {
let mut fields = vec![];
let mut ddpos = None;
while !self.check(&token::CloseDelim(token::Paren)) {
if ddpos.is_none() && self.eat(&token::DotDot) {
ddpos = Some(fields.len());
if self.eat(&token::Comma) {
// `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
fields.push(self.parse_pat()?);
}
} else if ddpos.is_some() && self.eat(&token::DotDot) {
// Emit a friendly error, ignore `..` and continue parsing
self.span_err(self.prev_span, "`..` can only be used once per \
tuple or tuple struct pattern");
} else {
fields.push(self.parse_pat()?);
}
if !self.check(&token::CloseDelim(token::Paren)) ||
(unary_needs_comma && fields.len() == 1 && ddpos.is_none()) {
self.expect(&token::Comma)?;
}
}
Ok((fields, ddpos))
}
fn parse_pat_vec_elements(
&mut self,
) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
let mut before = Vec::new();
let mut slice = None;
let mut after = Vec::new();
let mut first = true;
let mut before_slice = true;
while self.token != token::CloseDelim(token::Bracket) {
if first {
first = false;
} else {
self.expect(&token::Comma)?;
if self.token == token::CloseDelim(token::Bracket)
&& (before_slice || !after.is_empty()) {
break
}
}
if before_slice {
if self.eat(&token::DotDot) {
if self.check(&token::Comma) ||
self.check(&token::CloseDelim(token::Bracket)) {
slice = Some(P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Wild,
span: self.span,
}));
before_slice = false;
}
continue
}
}
let subpat = self.parse_pat()?;
if before_slice && self.eat(&token::DotDot) {
slice = Some(subpat);
before_slice = false;
} else if before_slice {
before.push(subpat);
} else {
after.push(subpat);
}
}
Ok((before, slice, after))
}
/// Parse the fields of a struct-like pattern
fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<codemap::Spanned<ast::FieldPat>>, bool)> {
let mut fields = Vec::new();
let mut etc = false;
let mut first = true;
while self.token != token::CloseDelim(token::Brace) {
if first {
first = false;
} else {
self.expect(&token::Comma)?;
// accept trailing commas
if self.check(&token::CloseDelim(token::Brace)) { break }
}
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let hi;
if self.check(&token::DotDot) || self.token == token::DotDotDot {
if self.token == token::DotDotDot { // Issue #46718
let mut err = self.struct_span_err(self.span,
"expected field pattern, found `...`");
err.span_suggestion(self.span,
"to omit remaining fields, use one fewer `.`",
"..".to_owned());
err.emit();
}
self.bump();
if self.token != token::CloseDelim(token::Brace) {
let token_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected `{}`, found `{}`", "}",
token_str)))
}
etc = true;
break;
}
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
// Parsing a pattern of the form "fieldname: pat"
let fieldname = self.parse_field_name()?;
self.bump();
let pat = self.parse_pat()?;
hi = pat.span;
(pat, fieldname, false)
} else {
// Parsing a pattern of the form "(box) (ref) (mut) fieldname"
let is_box = self.eat_keyword(keywords::Box);
let boxed_span = self.span;
let is_ref = self.eat_keyword(keywords::Ref);
let is_mut = self.eat_keyword(keywords::Mut);
let fieldname = self.parse_ident()?;
hi = self.prev_span;
let bind_type = match (is_ref, is_mut) {
(true, true) => BindingMode::ByRef(Mutability::Mutable),
(true, false) => BindingMode::ByRef(Mutability::Immutable),
(false, true) => BindingMode::ByValue(Mutability::Mutable),
(false, false) => BindingMode::ByValue(Mutability::Immutable),
};
let fieldpath = codemap::Spanned{span:self.prev_span, node:fieldname};
let fieldpat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(bind_type, fieldpath, None),
span: boxed_span.to(hi),
});
let subpat = if is_box {
P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Box(fieldpat),
span: lo.to(hi),
})
} else {
fieldpat
};
(subpat, fieldname, true)
};
fields.push(codemap::Spanned { span: lo.to(hi),
node: ast::FieldPat {
ident: fieldname,
pat: subpat,
is_shorthand,
attrs: attrs.into(),
}
});
}
return Ok((fields, etc));
}
fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
if self.token.is_path_start() {
let lo = self.span;
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
let hi = self.prev_span;
Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
} else {
self.parse_pat_literal_maybe_minus()
}
}
// helper function to decide whether to parse as ident binding or to try to do
// something more complex like range patterns
fn parse_as_ident(&mut self) -> bool {
self.look_ahead(1, |t| match *t {
token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
// ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
// range pattern branch
token::DotDot => None,
_ => Some(true),
}).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
token::Comma | token::CloseDelim(token::Bracket) => true,
_ => false,
}))
}
/// Parse a pattern.
pub fn parse_pat(&mut self) -> PResult<'a, P<Pat>> {
maybe_whole!(self, NtPat, |x| x);
let lo = self.span;
let pat;
match self.token {
token::Underscore => {
// Parse _
self.bump();
pat = PatKind::Wild;
}
token::BinOp(token::And) | token::AndAnd => {
// Parse &pat / &mut pat
self.expect_and()?;
let mutbl = self.parse_mutability();
if let token::Lifetime(ident) = self.token {
return Err(self.fatal(&format!("unexpected lifetime `{}` in pattern", ident)));
}
let subpat = self.parse_pat()?;
pat = PatKind::Ref(subpat, mutbl);
}
token::OpenDelim(token::Paren) => {
// Parse (pat,pat,pat,...) as tuple pattern
self.bump();
let (fields, ddpos) = self.parse_pat_tuple_elements(true)?;
self.expect(&token::CloseDelim(token::Paren))?;
pat = PatKind::Tuple(fields, ddpos);
}
token::OpenDelim(token::Bracket) => {
// Parse [pat,pat,...] as slice pattern
self.bump();
let (before, slice, after) = self.parse_pat_vec_elements()?;
self.expect(&token::CloseDelim(token::Bracket))?;
pat = PatKind::Slice(before, slice, after);
}
// At this point, token != _, &, &&, (, [
_ => if self.eat_keyword(keywords::Mut) {
// Parse mut ident @ pat / mut ref ident @ pat
let mutref_span = self.prev_span.to(self.span);
let binding_mode = if self.eat_keyword(keywords::Ref) {
self.diagnostic()
.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
.span_suggestion(mutref_span, "try switching the order", "ref mut".into())
.emit();
BindingMode::ByRef(Mutability::Mutable)
} else {
BindingMode::ByValue(Mutability::Mutable)
};
pat = self.parse_pat_ident(binding_mode)?;
} else if self.eat_keyword(keywords::Ref) {
// Parse ref ident @ pat / ref mut ident @ pat
let mutbl = self.parse_mutability();
pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
} else if self.eat_keyword(keywords::Box) {
// Parse box pat
let subpat = self.parse_pat()?;
pat = PatKind::Box(subpat);
} else if self.token.is_ident() && !self.token.is_reserved_ident() &&
self.parse_as_ident() {
// Parse ident @ pat
// This can give false positives and parse nullary enums,
// they are dealt with later in resolve
let binding_mode = BindingMode::ByValue(Mutability::Immutable);
pat = self.parse_pat_ident(binding_mode)?;
} else if self.token.is_path_start() {
// Parse pattern starting with a path
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
match self.token {
token::Not if qself.is_none() => {
// Parse macro invocation
self.bump();
let (_, tts) = self.expect_delimited_token_tree()?;
let mac = respan(lo.to(self.prev_span), Mac_ { path: path, tts: tts });
pat = PatKind::Mac(mac);
}
token::DotDotDot | token::DotDotEq | token::DotDot => {
let end_kind = match self.token {
token::DotDot => RangeEnd::Excluded,
token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
_ => panic!("can only parse `..`/`...`/`..=` for ranges \
(checked above)"),
};
// Parse range
let span = lo.to(self.prev_span);
let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
self.bump();
let end = self.parse_pat_range_end()?;
pat = PatKind::Range(begin, end, end_kind);
}
token::OpenDelim(token::Brace) => {
if qself.is_some() {
return Err(self.fatal("unexpected `{` after qualified path"));
}
// Parse struct pattern
self.bump();
let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt();
(vec![], false)
});
self.bump();
pat = PatKind::Struct(path, fields, etc);
}
token::OpenDelim(token::Paren) => {
if qself.is_some() {
return Err(self.fatal("unexpected `(` after qualified path"));
}
// Parse tuple struct or enum pattern
self.bump();
let (fields, ddpos) = self.parse_pat_tuple_elements(false)?;
self.expect(&token::CloseDelim(token::Paren))?;
pat = PatKind::TupleStruct(path, fields, ddpos)
}
_ => pat = PatKind::Path(qself, path),
}
} else {
// Try to parse everything else as literal with optional minus
match self.parse_pat_literal_maybe_minus() {
Ok(begin) => {
if self.eat(&token::DotDotDot) {
let end = self.parse_pat_range_end()?;
pat = PatKind::Range(begin, end,
RangeEnd::Included(RangeSyntax::DotDotDot));
} else if self.eat(&token::DotDotEq) {
let end = self.parse_pat_range_end()?;
pat = PatKind::Range(begin, end,
RangeEnd::Included(RangeSyntax::DotDotEq));
} else if self.eat(&token::DotDot) {
let end = self.parse_pat_range_end()?;
pat = PatKind::Range(begin, end, RangeEnd::Excluded);
} else {
pat = PatKind::Lit(begin);
}
}
Err(mut err) => {
self.cancel(&mut err);
let msg = format!("expected pattern, found {}", self.this_token_descr());
return Err(self.fatal(&msg));
}
}
}
}
let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
Ok(P(pat))
}
/// Parse ident or ident @ pat
/// used by the copy foo and ref foo patterns to give a good
/// error message when parsing mistakes like ref foo(a,b)
fn parse_pat_ident(&mut self,
binding_mode: ast::BindingMode)
-> PResult<'a, PatKind> {
let ident_span = self.span;
let ident = self.parse_ident()?;
let name = codemap::Spanned{span: ident_span, node: ident};
let sub = if self.eat(&token::At) {
Some(self.parse_pat()?)
} else {
None
};
// just to be friendly, if they write something like
// ref Some(i)
// we end up here with ( as the current token. This shortly
// leads to a parse error. Note that if there is no explicit
// binding mode then we do not end up here, because the lookahead
// will direct us over to parse_enum_variant()
if self.token == token::OpenDelim(token::Paren) {
return Err(self.span_fatal(
self.prev_span,
"expected identifier, found enum pattern"))
}
Ok(PatKind::Ident(binding_mode, name, sub))
}
/// Parse a local variable declaration
fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
let lo = self.prev_span;
let pat = self.parse_pat()?;
let (err, ty) = if self.eat(&token::Colon) {
// Save the state of the parser before parsing type normally, in case there is a `:`
// instead of an `=` typo.
let parser_snapshot_before_type = self.clone();
let colon_sp = self.prev_span;
match self.parse_ty() {
Ok(ty) => (None, Some(ty)),
Err(mut err) => {
// Rewind to before attempting to parse the type and continue parsing
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
let snippet = self.sess.codemap().span_to_snippet(pat.span).unwrap();
err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
(Some((parser_snapshot_after_type, colon_sp, err)), None)
}
}
} else {
(None, None)
};
let init = match (self.parse_initializer(err.is_some()), err) {
(Ok(init), None) => { // init parsed, ty parsed
init
}
(Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
// Could parse the type as if it were the initializer, it is likely there was a
// typo in the code: `:` instead of `=`. Add suggestion and emit the error.
err.span_suggestion_short(colon_sp,
"use `=` if you meant to assign",
"=".to_string());
err.emit();
// As this was parsed successfuly, continue as if the code has been fixed for the
// rest of the file. It will still fail due to the emitted error, but we avoid
// extra noise.
init
}
(Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
init_err.cancel();
// Couldn't parse the type nor the initializer, only raise the type error and
// return to the parser state before parsing the type as the initializer.
// let x: <parse_error>;
mem::replace(self, snapshot);
return Err(ty_err);
}
(Err(err), None) => { // init error, ty parsed
// Couldn't parse the initializer and we're not attempting to recover a failed
// parse of the type, return the error.
return Err(err);
}
};
let hi = if self.token == token::Semi {
self.span
} else {
self.prev_span
};
Ok(P(ast::Local {
ty,
pat,
init,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
attrs,
}))
}
/// Parse a structure field
fn parse_name_and_ty(&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute>)
-> PResult<'a, StructField> {
let name = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
Ok(StructField {
span: lo.to(self.prev_span),
ident: Some(name),
vis,
id: ast::DUMMY_NODE_ID,
ty,
attrs,
})
}
/// Emit an expected item after attributes error.
fn expected_item_err(&self, attrs: &[Attribute]) {
let message = match attrs.last() {
Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
_ => "expected item after attributes",
};
self.span_err(self.prev_span, message);
}
/// Parse a statement. This stops just before trailing semicolons on everything but items.
/// e.g. a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
Ok(self.parse_stmt_(true))
}
// Eat tokens until we can be relatively sure we reached the end of the
// statement. This is something of a best-effort heuristic.
//
// We terminate when we find an unmatched `}` (without consuming it).
fn recover_stmt(&mut self) {
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
}
// If `break_on_semi` is `Break`, then we will stop consuming tokens after
// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
// approximate - it can mean we break too early due to macros, but that
// shoud only lead to sub-optimal recovery, not inaccurate parsing).
//
// If `break_on_block` is `Break`, then we will stop consuming tokens
// after finding (and consuming) a brace-delimited block.
fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
let mut brace_depth = 0;
let mut bracket_depth = 0;
let mut in_block = false;
debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
break_on_semi, break_on_block);
loop {
debug!("recover_stmt_ loop {:?}", self.token);
match self.token {
token::OpenDelim(token::DelimToken::Brace) => {
brace_depth += 1;
self.bump();
if break_on_block == BlockMode::Break &&
brace_depth == 1 &&
bracket_depth == 0 {
in_block = true;
}
}
token::OpenDelim(token::DelimToken::Bracket) => {
bracket_depth += 1;
self.bump();
}
token::CloseDelim(token::DelimToken::Brace) => {
if brace_depth == 0 {
debug!("recover_stmt_ return - close delim {:?}", self.token);
return;
}
brace_depth -= 1;
self.bump();
if in_block && bracket_depth == 0 && brace_depth == 0 {
debug!("recover_stmt_ return - block end {:?}", self.token);
return;
}
}
token::CloseDelim(token::DelimToken::Bracket) => {
bracket_depth -= 1;
if bracket_depth < 0 {
bracket_depth = 0;
}
self.bump();
}
token::Eof => {
debug!("recover_stmt_ return - Eof");
return;
}
token::Semi => {
self.bump();
if break_on_semi == SemiColonMode::Break &&
brace_depth == 0 &&
bracket_depth == 0 {
debug!("recover_stmt_ return - Semi");
return;
}
}
_ => {
self.bump()
}
}
}
}
fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
None
})
}
fn is_catch_expr(&mut self) -> bool {
self.token.is_keyword(keywords::Do) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
// prevent `while catch {} {}`, `if catch {} {} else {}`, etc.
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
}
fn is_union_item(&self) -> bool {
self.token.is_keyword(keywords::Union) &&
self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
}
fn is_crate_vis(&self) -> bool {
self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
}
fn is_extern_non_path(&self) -> bool {
self.token.is_keyword(keywords::Extern) && self.look_ahead(1, |t| t != &token::ModSep)
}
fn is_auto_trait_item(&mut self) -> bool {
// auto trait
(self.token.is_keyword(keywords::Auto)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
|| // unsafe auto trait
(self.token.is_keyword(keywords::Unsafe) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
}
fn is_defaultness(&self) -> bool {
// `pub` is included for better error messages
self.token.is_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
t.is_keyword(keywords::Const) ||
t.is_keyword(keywords::Fn) ||
t.is_keyword(keywords::Unsafe) ||
t.is_keyword(keywords::Extern) ||
t.is_keyword(keywords::Type) ||
t.is_keyword(keywords::Pub))
}
fn eat_defaultness(&mut self) -> bool {
let is_defaultness = self.is_defaultness();
if is_defaultness {
self.bump()
} else {
self.expected_tokens.push(TokenType::Keyword(keywords::Default));
}
is_defaultness
}
fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
-> PResult<'a, Option<P<Item>>> {
let token_lo = self.span;
let (ident, def) = match self.token {
token::Ident(ident) if ident.name == keywords::Macro.name() => {
self.bump();
let ident = self.parse_ident()?;
let tokens = if self.check(&token::OpenDelim(token::Brace)) {
match self.parse_token_tree() {
TokenTree::Delimited(_, ref delimited) => delimited.stream(),
_ => unreachable!(),
}
} else if self.check(&token::OpenDelim(token::Paren)) {
let args = self.parse_token_tree();
let body = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_token_tree()
} else {
self.unexpected()?;
unreachable!()
};
TokenStream::concat(vec![
args.into(),
TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
body.into(),
])
} else {
self.unexpected()?;
unreachable!()
};
(ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
}
token::Ident(ident) if ident.name == "macro_rules" &&
self.look_ahead(1, |t| *t == token::Not) => {
let prev_span = self.prev_span;
self.complain_if_pub_macro(vis, prev_span);
self.bump();
self.bump();
let ident = self.parse_ident()?;
let (delim, tokens) = self.expect_delimited_token_tree()?;
if delim != token::Brace {
if !self.eat(&token::Semi) {
let msg = "macros that expand to items must either \
be surrounded with braces or followed by a semicolon";
self.span_err(self.prev_span, msg);
}
}
(ident, ast::MacroDef { tokens: tokens, legacy: true })
}
_ => return Ok(None),
};
let span = lo.to(self.prev_span);
Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
}
fn parse_stmt_without_recovery(&mut self,
macro_legacy_warnings: bool)
-> PResult<'a, Option<Stmt>> {
maybe_whole!(self, NtStmt, |x| Some(x));
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
Ok(Some(if self.eat_keyword(keywords::Let) {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Local(self.parse_local(attrs.into())?),
span: lo.to(self.prev_span),
}
} else if let Some(macro_def) = self.eat_macro_def(&attrs, &Visibility::Inherited, lo)? {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Item(macro_def),
span: lo.to(self.prev_span),
}
// Starts like a simple path, being careful to avoid contextual keywords
// such as a union items, item with `crate` visibility or auto trait items.
// Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
// like a path (1 token), but it fact not a path.
// `union::b::c` - path, `union U { ... }` - not a path.
// `crate::b::c` - path, `crate struct S;` - not a path.
// `extern::b::c` - path, `extern crate c;` - not a path.
} else if self.token.is_path_start() &&
!self.token.is_qpath_start() &&
!self.is_union_item() &&
!self.is_crate_vis() &&
!self.is_extern_non_path() &&
!self.is_auto_trait_item() {
let pth = self.parse_path(PathStyle::Expr)?;
if !self.eat(&token::Not) {
let expr = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_struct_expr(lo, pth, ThinVec::new())?
} else {
let hi = self.prev_span;
self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
};
let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
})?;
return Ok(Some(Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Expr(expr),
span: lo.to(self.prev_span),
}));
}
// it's a macro invocation
let id = match self.token {
token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
_ => self.parse_ident()?,
};
// check that we're pointing at delimiters (need to check
// again after the `if`, because of `parse_ident`
// consuming more tokens).
let delim = match self.token {
token::OpenDelim(delim) => delim,
_ => {
// we only expect an ident if we didn't parse one
// above.
let ident_str = if id.name == keywords::Invalid.name() {
"identifier, "
} else {
""
};
let tok_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected {}`(` or `{{`, found `{}`",
ident_str,
tok_str)))
},
};
let (_, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
let style = if delim == token::Brace {
MacStmtStyle::Braces
} else {
MacStmtStyle::NoBraces
};
if id.name == keywords::Invalid.name() {
let mac = respan(lo.to(hi), Mac_ { path: pth, tts: tts });
let node = if delim == token::Brace ||
self.token == token::Semi || self.token == token::Eof {
StmtKind::Mac(P((mac, style, attrs.into())))
}
// We used to incorrectly stop parsing macro-expanded statements here.
// If the next token will be an error anyway but could have parsed with the
// earlier behavior, stop parsing here and emit a warning to avoid breakage.
else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
// These can continue an expression, so we can't stop parsing and warn.
token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
token::BinOp(token::Minus) | token::BinOp(token::Star) |
token::BinOp(token::And) | token::BinOp(token::Or) |
token::AndAnd | token::OrOr |
token::DotDot | token::DotDotDot | token::DotDotEq => false,
_ => true,
} {
self.warn_missing_semicolon();
StmtKind::Mac(P((mac, style, attrs.into())))
} else {
let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new());
let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
StmtKind::Expr(e)
};
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
node,
}
} else {
// if it has a special ident, it's definitely an item
//
// Require a semicolon or braces.
if style != MacStmtStyle::Braces {
if !self.eat(&token::Semi) {
self.span_err(self.prev_span,
"macros that expand to items must \
either be surrounded with braces or \
followed by a semicolon");
}
}
let span = lo.to(hi);
Stmt {
id: ast::DUMMY_NODE_ID,
span,
node: StmtKind::Item({
self.mk_item(
span, id /*id is good here*/,
ItemKind::Mac(respan(span, Mac_ { path: pth, tts: tts })),
Visibility::Inherited,
attrs)
}),
}
}
} else {
// FIXME: Bad copy of attrs
let old_directory_ownership =
mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
let item = self.parse_item_(attrs.clone(), false, true)?;
self.directory.ownership = old_directory_ownership;
match item {
Some(i) => Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(i.span),
node: StmtKind::Item(i),
},
None => {
let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
if !attrs.is_empty() {
if s.prev_token_kind == PrevTokenKind::DocComment {
s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
} else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
s.span_err(s.span, "expected statement after outer attribute");
}
}
};
// Do not attempt to parse an expression if we're done here.
if self.token == token::Semi {
unused_attrs(&attrs, self);
self.bump();
return Ok(None);
}
if self.token == token::CloseDelim(token::Brace) {
unused_attrs(&attrs, self);
return Ok(None);
}
// Remainder are line-expr stmts.
let e = self.parse_expr_res(
Restrictions::STMT_EXPR, Some(attrs.into()))?;
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(e.span),
node: StmtKind::Expr(e),
}
}
}
}))
}
/// Is this expression a successfully-parsed statement?
fn expr_is_complete(&mut self, e: &Expr) -> bool {
self.restrictions.contains(Restrictions::STMT_EXPR) &&
!classify::expr_requires_semi_to_be_stmt(e)
}
/// Parse a block. No inner attrs are allowed.
pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
maybe_whole!(self, NtBlock, |x| x);
let lo = self.span;
if !self.eat(&token::OpenDelim(token::Brace)) {
let sp = self.span;
let tok = self.this_token_to_string();
let mut e = self.span_fatal(sp, &format!("expected `{{`, found `{}`", tok));
// Check to see if the user has written something like
//
// if (cond)
// bar;
//
// Which is valid in other languages, but not Rust.
match self.parse_stmt_without_recovery(false) {
Ok(Some(stmt)) => {
let mut stmt_span = stmt.span;
// expand the span to include the semicolon, if it exists
if self.eat(&token::Semi) {
stmt_span = stmt_span.with_hi(self.prev_span.hi());
}
let sugg = pprust::to_string(|s| {
use print::pprust::{PrintState, INDENT_UNIT};
s.ibox(INDENT_UNIT)?;
s.bopen()?;
s.print_stmt(&stmt)?;
s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
});
e.span_suggestion(stmt_span, "try placing this code inside a block", sugg);
}
Err(mut e) => {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
self.cancel(&mut e);
}
_ => ()
}
return Err(e);
}
self.parse_block_tail(lo, BlockCheckMode::Default)
}
/// Parse a block. Inner attrs are allowed.
fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
let lo = self.span;
self.expect(&token::OpenDelim(token::Brace))?;
Ok((self.parse_inner_attributes()?,
self.parse_block_tail(lo, BlockCheckMode::Default)?))
}
/// Parse the rest of a block expression or function body
/// Precondition: already parsed the '{'.
fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
let mut stmts = vec![];
let mut recovered = false;
while !self.eat(&token::CloseDelim(token::Brace)) {
let stmt = match self.parse_full_stmt(false) {
Err(mut err) => {
err.emit();
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
self.eat(&token::CloseDelim(token::Brace));
recovered = true;
break;
}
Ok(stmt) => stmt,
};
if let Some(stmt) = stmt {
stmts.push(stmt);
} else if self.token == token::Eof {
break;
} else {
// Found only `;` or `}`.
continue;
};
}
Ok(P(ast::Block {
stmts,
id: ast::DUMMY_NODE_ID,
rules: s,
span: lo.to(self.prev_span),
recovered,
}))
}
/// Parse a statement, including the trailing semicolon.
pub fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
Some(stmt) => stmt,
None => return Ok(None),
};
match stmt.node {
StmtKind::Expr(ref expr) if self.token != token::Eof => {
// expression without semicolon
if classify::expr_requires_semi_to_be_stmt(expr) {
// Just check for errors and recover; do not eat semicolon yet.
if let Err(mut e) =
self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
{
e.emit();
self.recover_stmt();
}
}
}
StmtKind::Local(..) => {
// We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
if macro_legacy_warnings && self.token != token::Semi {
self.warn_missing_semicolon();
} else {
self.expect_one_of(&[token::Semi], &[])?;
}
}
_ => {}
}
if self.eat(&token::Semi) {
stmt = stmt.add_trailing_semicolon();
}
stmt.span = stmt.span.with_hi(self.prev_span.hi());
Ok(Some(stmt))
}
fn warn_missing_semicolon(&self) {
self.diagnostic().struct_span_warn(self.span, {
&format!("expected `;`, found `{}`", self.this_token_to_string())
}).note({
"This was erroneously allowed and will become a hard error in a future release"
}).emit();
}
fn err_dotdotdot_syntax(&self, span: Span) {
self.diagnostic().struct_span_err(span, {
"`...` syntax cannot be used in expressions"
}).help({
"Use `..` if you need an exclusive range (a < b)"
}).help({
"or `..=` if you need an inclusive range (a <= b)"
}).emit();
}
// Parse bounds of a type parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
// BOUND = TY_BOUND | LT_BOUND
// LT_BOUND = LIFETIME (e.g. `'a`)
// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g. `?for<'a: 'b> m::Trait<'a>`)
fn parse_ty_param_bounds_common(&mut self, allow_plus: bool) -> PResult<'a, TyParamBounds> {
let mut bounds = Vec::new();
loop {
// This needs to be syncronized with `Token::can_begin_bound`.
let is_bound_start = self.check_path() || self.check_lifetime() ||
self.check(&token::Question) ||
self.check_keyword(keywords::For) ||
self.check(&token::OpenDelim(token::Paren));
if is_bound_start {
let has_parens = self.eat(&token::OpenDelim(token::Paren));
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.token.is_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(RegionTyParamBound(self.expect_lifetime()));
} else {
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
bounds.push(TraitTyParamBound(poly_trait, modifier));
}
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
if let Some(&RegionTyParamBound(..)) = bounds.last() {
self.span_err(self.prev_span,
"parenthesized lifetime bounds are not supported");
}
}
} else {
break
}
if !allow_plus || !self.eat(&token::BinOp(token::Plus)) {
break
}
}
return Ok(bounds);
}
fn parse_ty_param_bounds(&mut self) -> PResult<'a, TyParamBounds> {
self.parse_ty_param_bounds_common(true)
}
// Parse bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
// BOUND = LT_BOUND (e.g. `'a`)
fn parse_lt_param_bounds(&mut self) -> Vec<Lifetime> {
let mut lifetimes = Vec::new();
while self.check_lifetime() {
lifetimes.push(self.expect_lifetime());
if !self.eat(&token::BinOp(token::Plus)) {
break
}
}
lifetimes
}
/// Matches typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?
fn parse_ty_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, TyParam> {
let span = self.span;
let ident = self.parse_ident()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_ty_param_bounds()?
} else {
Vec::new()
};
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
};
Ok(TyParam {
attrs: preceding_attrs.into(),
ident,
id: ast::DUMMY_NODE_ID,
bounds,
default,
span,
})
}
/// Parses the following grammar:
/// TraitItemAssocTy = Ident ["<"...">"] [":" [TyParamBounds]] ["where" ...] ["=" Ty]
fn parse_trait_item_assoc_ty(&mut self, preceding_attrs: Vec<Attribute>)
-> PResult<'a, (ast::Generics, TyParam)> {
let span = self.span;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_ty_param_bounds()?
} else {
Vec::new()
};
generics.where_clause = self.parse_where_clause()?;
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
};
self.expect(&token::Semi)?;
Ok((generics, TyParam {
attrs: preceding_attrs.into(),
ident,
id: ast::DUMMY_NODE_ID,
bounds,
default,
span,
}))
}
/// Parses (possibly empty) list of lifetime and type parameters, possibly including
/// trailing comma and erroneous trailing attributes.
pub fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
let mut params = Vec::new();
let mut seen_ty_param = false;
loop {
let attrs = self.parse_outer_attributes()?;
if self.check_lifetime() {
let lifetime = self.expect_lifetime();
// Parse lifetime parameter.
let bounds = if self.eat(&token::Colon) {
self.parse_lt_param_bounds()
} else {
Vec::new()
};
params.push(ast::GenericParam::Lifetime(LifetimeDef {
attrs: attrs.into(),
lifetime,
bounds,
}));
if seen_ty_param {
self.span_err(self.prev_span,
"lifetime parameters must be declared prior to type parameters");
}
} else if self.check_ident() {
// Parse type parameter.
params.push(ast::GenericParam::Type(self.parse_ty_param(attrs)?));
seen_ty_param = true;
} else {
// Check for trailing attributes and stop parsing.
if !attrs.is_empty() {
let param_kind = if seen_ty_param { "type" } else { "lifetime" };
self.span_err(attrs[0].span,
&format!("trailing attribute after {} parameters", param_kind));
}
break
}
if !self.eat(&token::Comma) {
break
}
}
Ok(params)
}
/// Parse a set of optional generic type parameter declarations. Where
/// clauses are not parsed here, and must be added later via
/// `parse_where_clause()`.
///
/// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
/// | ( < lifetimes , typaramseq ( , )? > )
/// where typaramseq = ( typaram ) | ( typaram , typaramseq )
pub fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
maybe_whole!(self, NtGenerics, |x| x);
let span_lo = self.span;
if self.eat_lt() {
let params = self.parse_generic_params()?;
self.expect_gt()?;
Ok(ast::Generics {
params,
where_clause: WhereClause {
id: ast::DUMMY_NODE_ID,
predicates: Vec::new(),
span: syntax_pos::DUMMY_SP,
},
span: span_lo.to(self.prev_span),
})
} else {
Ok(ast::Generics::default())
}
}
/// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
/// possibly including trailing comma.
fn parse_generic_args(&mut self) -> PResult<'a, (Vec<Lifetime>, Vec<P<Ty>>, Vec<TypeBinding>)> {
let mut lifetimes = Vec::new();
let mut types = Vec::new();
let mut bindings = Vec::new();
let mut seen_type = false;
let mut seen_binding = false;
loop {
if self.check_lifetime() && self.look_ahead(1, |t| t != &token::BinOp(token::Plus)) {
// Parse lifetime argument.
lifetimes.push(self.expect_lifetime());
if seen_type || seen_binding {
self.span_err(self.prev_span,
"lifetime parameters must be declared prior to type parameters");
}
} else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
// Parse associated type binding.
let lo = self.span;
let ident = self.parse_ident()?;
self.bump();
let ty = self.parse_ty()?;
bindings.push(TypeBinding {
id: ast::DUMMY_NODE_ID,
ident,
ty,
span: lo.to(self.prev_span),
});
seen_binding = true;
} else if self.check_type() {
// Parse type argument.
types.push(self.parse_ty()?);
if seen_binding {
self.span_err(types[types.len() - 1].span,
"type parameters must be declared prior to associated type bindings");
}
seen_type = true;
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
Ok((lifetimes, types, bindings))
}
/// Parses an optional `where` clause and places it in `generics`.
///
/// ```ignore (only-for-syntax-highlight)
/// where T : Trait<U, V> + 'b, 'a : 'b
/// ```
pub fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
maybe_whole!(self, NtWhereClause, |x| x);
let mut where_clause = WhereClause {
id: ast::DUMMY_NODE_ID,
predicates: Vec::new(),
span: syntax_pos::DUMMY_SP,
};
if !self.eat_keyword(keywords::Where) {
return Ok(where_clause);
}
let lo = self.prev_span;
// This is a temporary future proofing.
//
// We are considering adding generics to the `where` keyword as an alternative higher-rank
// parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
// change, for now we refuse to parse `where < (ident | lifetime) (> | , | :)`.
if token::Lt == self.token {
let ident_or_lifetime = self.look_ahead(1, |t| t.is_ident() || t.is_lifetime());
if ident_or_lifetime {
let gt_comma_or_colon = self.look_ahead(2, |t| {
*t == token::Gt || *t == token::Comma || *t == token::Colon
});
if gt_comma_or_colon {
self.span_err(self.span, "syntax `where<T>` is reserved for future use");
}
}
}
loop {
let lo = self.span;
if self.check_lifetime() && self.look_ahead(1, |t| t != &token::BinOp(token::Plus)) {
let lifetime = self.expect_lifetime();
// Bounds starting with a colon are mandatory, but possibly empty.
self.expect(&token::Colon)?;
let bounds = self.parse_lt_param_bounds();
where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: lo.to(self.prev_span),
lifetime,
bounds,
}
));
} else if self.check_type() {
// Parse optional `for<'a, 'b>`.
// This `for` is parsed greedily and applies to the whole predicate,
// the bounded type can have its own `for` applying only to it.
// Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
// Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
// Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
// Parse type with mandatory colon and (possibly empty) bounds,
// or with mandatory equality sign and the second type.
let ty = self.parse_ty()?;
if self.eat(&token::Colon) {
let bounds = self.parse_ty_param_bounds()?;
where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: lo.to(self.prev_span),
bound_generic_params: lifetime_defs,
bounded_ty: ty,
bounds,
}
));
// FIXME: Decide what should be used here, `=` or `==`.
} else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
let rhs_ty = self.parse_ty()?;
where_clause.predicates.push(ast::WherePredicate::EqPredicate(
ast::WhereEqPredicate {
span: lo.to(self.prev_span),
lhs_ty: ty,
rhs_ty,
id: ast::DUMMY_NODE_ID,
}
));
} else {
return self.unexpected();
}
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
where_clause.span = lo.to(self.prev_span);
Ok(where_clause)
}
fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool)
-> PResult<'a, (Vec<Arg> , bool)> {
let sp = self.span;
let mut variadic = false;
let args: Vec<Option<Arg>> =
self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| {
if p.token == token::DotDotDot {
p.bump();
if allow_variadic {
if p.token != token::CloseDelim(token::Paren) {
let span = p.span;
p.span_err(span,
"`...` must be last in argument list for variadic function");
}
} else {
let span = p.span;
p.span_err(span,
"only foreign functions are allowed to be variadic");
}
variadic = true;
Ok(None)
} else {
match p.parse_arg_general(named_args) {
Ok(arg) => Ok(Some(arg)),
Err(mut e) => {
e.emit();
let lo = p.prev_span;
// Skip every token until next possible arg or end.
p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
// Create a placeholder argument for proper arg count (#34264).
let span = lo.to(p.prev_span);
Ok(Some(dummy_arg(span)))
}
}
}
}
)?;
let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
if variadic && args.is_empty() {
self.span_err(sp,
"variadic function must be declared with at least one named argument");
}
Ok((args, variadic))
}
/// Parse the argument list and result type of a function declaration
pub fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<'a, P<FnDecl>> {
let (args, variadic) = self.parse_fn_args(true, allow_variadic)?;
let ret_ty = self.parse_ret_ty()?;
Ok(P(FnDecl {
inputs: args,
output: ret_ty,
variadic,
}))
}
/// Returns the parsed optional self argument and whether a self shortcut was used.
fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
let expect_ident = |this: &mut Self| match this.token {
// Preserve hygienic context.
token::Ident(ident) => { let sp = this.span; this.bump(); codemap::respan(sp, ident) }
_ => unreachable!()
};
let isolated_self = |this: &mut Self, n| {
this.look_ahead(n, |t| t.is_keyword(keywords::SelfValue)) &&
this.look_ahead(n + 1, |t| t != &token::ModSep)
};
// Parse optional self parameter of a method.
// Only a limited set of initial token sequences is considered self parameters, anything
// else is parsed as a normal function parameter list, so some lookahead is required.
let eself_lo = self.span;
let (eself, eself_ident) = match self.token {
token::BinOp(token::And) => {
// &self
// &mut self
// &'lt self
// &'lt mut self
// &not_self
if isolated_self(self, 1) {
self.bump();
(SelfKind::Region(None, Mutability::Immutable), expect_ident(self))
} else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
isolated_self(self, 2) {
self.bump();
self.bump();
(SelfKind::Region(None, Mutability::Mutable), expect_ident(self))
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
isolated_self(self, 2) {
self.bump();
let lt = self.expect_lifetime();
(SelfKind::Region(Some(lt), Mutability::Immutable), expect_ident(self))
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
isolated_self(self, 3) {
self.bump();
let lt = self.expect_lifetime();
self.bump();
(SelfKind::Region(Some(lt), Mutability::Mutable), expect_ident(self))
} else {
return Ok(None);
}
}
token::BinOp(token::Star) => {
// *self
// *const self
// *mut self
// *not_self
// Emit special error for `self` cases.
if isolated_self(self, 1) {
self.bump();
self.span_err(self.span, "cannot pass `self` by raw pointer");
(SelfKind::Value(Mutability::Immutable), expect_ident(self))
} else if self.look_ahead(1, |t| t.is_mutability()) &&
isolated_self(self, 2) {
self.bump();
self.bump();
self.span_err(self.span, "cannot pass `self` by raw pointer");
(SelfKind::Value(Mutability::Immutable), expect_ident(self))
} else {
return Ok(None);
}
}
token::Ident(..) => {
if isolated_self(self, 0) {
// self
// self: TYPE
let eself_ident = expect_ident(self);
if self.eat(&token::Colon) {
let ty = self.parse_ty()?;
(SelfKind::Explicit(ty, Mutability::Immutable), eself_ident)
} else {
(SelfKind::Value(Mutability::Immutable), eself_ident)
}
} else if self.token.is_keyword(keywords::Mut) &&
isolated_self(self, 1) {
// mut self
// mut self: TYPE
self.bump();
let eself_ident = expect_ident(self);
if self.eat(&token::Colon) {
let ty = self.parse_ty()?;
(SelfKind::Explicit(ty, Mutability::Mutable), eself_ident)
} else {
(SelfKind::Value(Mutability::Mutable), eself_ident)
}
} else {
return Ok(None);
}
}
_ => return Ok(None),
};
let eself = codemap::respan(eself_lo.to(self.prev_span), eself);
Ok(Some(Arg::from_self(eself, eself_ident)))
}
/// Parse the parameter list and result type of a function that may have a `self` parameter.
fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
{
self.expect(&token::OpenDelim(token::Paren))?;
// Parse optional self argument
let self_arg = self.parse_self_arg()?;
// Parse the rest of the function parameter list.
let sep = SeqSep::trailing_allowed(token::Comma);
let fn_inputs = if let Some(self_arg) = self_arg {
if self.check(&token::CloseDelim(token::Paren)) {
vec![self_arg]
} else if self.eat(&token::Comma) {
let mut fn_inputs = vec![self_arg];
fn_inputs.append(&mut self.parse_seq_to_before_end(
&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
);
fn_inputs
} else {
return self.unexpected();
}
} else {
self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
};
// Parse closing paren and return type.
self.expect(&token::CloseDelim(token::Paren))?;
Ok(P(FnDecl {
inputs: fn_inputs,
output: self.parse_ret_ty()?,
variadic: false
}))
}
// parse the |arg, arg| header on a lambda
fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
let inputs_captures = {
if self.eat(&token::OrOr) {
Vec::new()
} else {
self.expect(&token::BinOp(token::Or))?;
let args = self.parse_seq_to_before_tokens(
&[&token::BinOp(token::Or), &token::OrOr],
SeqSep::trailing_allowed(token::Comma),
TokenExpectType::NoExpect,
|p| p.parse_fn_block_arg()
)?;
self.expect_or()?;
args
}
};
let output = self.parse_ret_ty()?;
Ok(P(FnDecl {
inputs: inputs_captures,
output,
variadic: false
}))
}
/// Parse the name and optional generic types of a function header.
fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
let id = self.parse_ident()?;
let generics = self.parse_generics()?;
Ok((id, generics))
}
fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
attrs: Vec<Attribute>) -> P<Item> {
P(Item {
ident,
attrs,
id: ast::DUMMY_NODE_ID,
node,
vis,
span,
tokens: None,
})
}
/// Parse an item-position function declaration.
fn parse_item_fn(&mut self,
unsafety: Unsafety,
constness: Spanned<Constness>,
abi: abi::Abi)
-> PResult<'a, ItemInfo> {
let (ident, mut generics) = self.parse_fn_header()?;
let decl = self.parse_fn_decl(false)?;
generics.where_clause = self.parse_where_clause()?;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
Ok((ident, ItemKind::Fn(decl, unsafety, constness, abi, generics, body), Some(inner_attrs)))
}
/// true if we are looking at `const ID`, false for things like `const fn` etc
pub fn is_const_item(&mut self) -> bool {
self.token.is_keyword(keywords::Const) &&
!self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
!self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
}
/// parses all the "front matter" for a `fn` declaration, up to
/// and including the `fn` keyword:
///
/// - `const fn`
/// - `unsafe fn`
/// - `const unsafe fn`
/// - `extern fn`
/// - etc
pub fn parse_fn_front_matter(&mut self)
-> PResult<'a, (Spanned<ast::Constness>,
ast::Unsafety,
abi::Abi)> {
let is_const_fn = self.eat_keyword(keywords::Const);
let const_span = self.prev_span;
let unsafety = self.parse_unsafety()?;
let (constness, unsafety, abi) = if is_const_fn {
(respan(const_span, Constness::Const), unsafety, Abi::Rust)
} else {
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
(respan(self.prev_span, Constness::NotConst), unsafety, abi)
};
self.expect_keyword(keywords::Fn)?;
Ok((constness, unsafety, abi))
}
/// Parse an impl item.
pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
maybe_whole!(self, NtImplItem, |x| x);
let attrs = self.parse_outer_attributes()?;
let (mut item, tokens) = self.collect_tokens(|this| {
this.parse_impl_item_(at_end, attrs)
})?;
// See `parse_item` for why this clause is here.
if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
item.tokens = Some(tokens);
}
Ok(item)
}
fn parse_impl_item_(&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
let lo = self.span;
let vis = self.parse_visibility(false)?;
let defaultness = self.parse_defaultness()?;
let (name, node, generics) = if self.eat_keyword(keywords::Type) {
// This parses the grammar:
// ImplItemAssocTy = Ident ["<"...">"] ["where" ...] "=" Ty ";"
let name = self.parse_ident()?;
let mut generics = self.parse_generics()?;
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::Eq)?;
let typ = self.parse_ty()?;
self.expect(&token::Semi)?;
(name, ast::ImplItemKind::Type(typ), generics)
} else if self.is_const_item() {
// This parses the grammar:
// ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
self.expect_keyword(keywords::Const)?;
let name = self.parse_ident()?;
self.expect(&token::Colon)?;
let typ = self.parse_ty()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr()?;
self.expect(&token::Semi)?;
(name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
} else {
let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
attrs.extend(inner_attrs);
(name, node, generics)
};
Ok(ImplItem {
id: ast::DUMMY_NODE_ID,
span: lo.to(self.prev_span),
ident: name,
vis,
defaultness,
attrs,
generics,
node,
tokens: None,
})
}
fn complain_if_pub_macro(&mut self, vis: &Visibility, sp: Span) {
if let Err(mut err) = self.complain_if_pub_macro_diag(vis, sp) {
err.emit();
}
}
fn complain_if_pub_macro_diag(&mut self, vis: &Visibility, sp: Span) -> PResult<'a, ()> {
match *vis {
Visibility::Inherited => Ok(()),
_ => {
let is_macro_rules: bool = match self.token {
token::Ident(sid) => sid.name == Symbol::intern("macro_rules"),
_ => false,
};
if is_macro_rules {
let mut err = self.diagnostic()
.struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
err.help("did you mean #[macro_export]?");
Err(err)
} else {
let mut err = self.diagnostic()
.struct_span_err(sp, "can't qualify macro invocation with `pub`");
err.help("try adjusting the macro to put `pub` inside the invocation");
Err(err)
}
}
}
}
fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span)
-> DiagnosticBuilder<'a>
{
// Given this code `path(`, it seems like this is not
// setting the visibility of a macro invocation, but rather
// a mistyped method declaration.
// Create a diagnostic pointing out that `fn` is missing.
//
// x | pub path(&self) {
// | ^ missing `fn`, `type`, or `const`
// pub path(
// ^^ `sp` below will point to this
let sp = prev_span.between(self.prev_span);
let mut err = self.diagnostic().struct_span_err(
sp,
&format!("missing `fn`, `type`, or `const` for {}-item declaration",
item_type));
err.span_label(sp, "missing `fn`, `type`, or `const`");
err
}
/// Parse a method or a macro invocation in a trait impl.
fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
-> PResult<'a, (Ident, Vec<ast::Attribute>, ast::Generics,
ast::ImplItemKind)> {
// code copied from parse_macro_use_or_failure... abstraction!
if self.token.is_path_start() && !self.is_extern_non_path() {
// Method macro.
let prev_span = self.prev_span;
let lo = self.span;
let pth = self.parse_path(PathStyle::Mod)?;
if pth.segments.len() == 1 {
if !self.eat(&token::Not) {
return Err(self.missing_assoc_item_kind_err("impl", prev_span));
}
} else {
self.expect(&token::Not)?;
}
self.complain_if_pub_macro(vis, prev_span);
// eat a matched-delimiter token tree:
*at_end = true;
let (delim, tts) = self.expect_delimited_token_tree()?;
if delim != token::Brace {
self.expect(&token::Semi)?
}
let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
ast::ImplItemKind::Macro(mac)))
} else {
let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
generics.where_clause = self.parse_where_clause()?;
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(ast::MethodSig {
abi,
unsafety,
constness,
decl,
}, body)))
}
}
/// Parse `trait Foo { ... }` or `trait Foo = Bar;`
fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
// Parse optional colon and supertrait bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_ty_param_bounds()?
} else {
Vec::new()
};
if self.eat(&token::Eq) {
// it's a trait alias
let bounds = self.parse_ty_param_bounds()?;
tps.where_clause = self.parse_where_clause()?;
self.expect(&token::Semi)?;
if unsafety != Unsafety::Normal {
self.span_err(self.prev_span, "trait aliases cannot be unsafe");
}
Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
} else {
// it's a normal trait
tps.where_clause = self.parse_where_clause()?;
self.expect(&token::OpenDelim(token::Brace))?;
let mut trait_items = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
let mut at_end = false;
match self.parse_trait_item(&mut at_end) {
Ok(item) => trait_items.push(item),
Err(mut e) => {
e.emit();
if !at_end {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
}
}
}
}
Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
}
}
/// Parses items implementations variants
/// impl<T> Foo { ... }
/// impl<T> ToString for &'static T { ... }
fn parse_item_impl(&mut self,
unsafety: ast::Unsafety,
defaultness: Defaultness) -> PResult<'a, ItemInfo> {
// First, parse type parameters if necessary.
let mut generics = self.parse_generics()?;
// Special case: if the next identifier that follows is '(', don't
// allow this to be parsed as a trait.
let could_be_trait = self.token != token::OpenDelim(token::Paren);
let neg_span = self.span;
let polarity = if self.eat(&token::Not) {
ast::ImplPolarity::Negative
} else {
ast::ImplPolarity::Positive
};
// Parse the trait.
let mut ty = self.parse_ty()?;
// Parse traits, if necessary.
let opt_trait = if could_be_trait && self.eat_keyword(keywords::For) {
// New-style trait. Reinterpret the type as a trait.
match ty.node {
TyKind::Path(None, ref path) => {
Some(TraitRef {
path: (*path).clone(),
ref_id: ty.id,
})
}
_ => {
self.span_err(ty.span, "not a trait");
None
}
}
} else {
if polarity == ast::ImplPolarity::Negative {
// This is a negated type implementation
// `impl !MyType {}`, which is not allowed.
self.span_err(neg_span, "inherent implementation can't be negated");
}
None
};
if opt_trait.is_some() {
ty = if self.eat(&token::DotDot) {
P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID })
} else {
self.parse_ty()?
}
}
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::OpenDelim(token::Brace))?;
let attrs = self.parse_inner_attributes()?;
let mut impl_items = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
let mut at_end = false;
match self.parse_impl_item(&mut at_end) {
Ok(item) => impl_items.push(item),
Err(mut e) => {
e.emit();
if !at_end {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
}
}
}
}
Ok((keywords::Invalid.ident(),
ItemKind::Impl(unsafety, polarity, defaultness, generics, opt_trait, ty, impl_items),
Some(attrs)))
}
fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
if self.eat_keyword(keywords::For) {
self.expect_lt()?;
let params = self.parse_generic_params()?;
self.expect_gt()?;
let first_non_lifetime_param_span = params.iter()
.filter_map(|param| match *param {
ast::GenericParam::Lifetime(_) => None,
ast::GenericParam::Type(ref t) => Some(t.span),
})
.next();
if let Some(span) = first_non_lifetime_param_span {
self.span_err(span, "only lifetime parameters can be used in this context");
}
Ok(params)
} else {
Ok(Vec::new())
}
}
/// Parse struct Foo { ... }
fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
let class_name = self.parse_ident()?;
let mut generics = self.parse_generics()?;
// There is a special case worth noting here, as reported in issue #17904.
// If we are parsing a tuple struct it is the case that the where clause
// should follow the field list. Like so:
//
// struct Foo<T>(T) where T: Copy;
//
// If we are parsing a normal record-style struct it is the case
// that the where clause comes before the body, and after the generics.
// So if we look ahead and see a brace or a where-clause we begin
// parsing a record style struct.
//
// Otherwise if we look ahead and see a paren we parse a tuple-style
// struct.
let vdata = if self.token.is_keyword(keywords::Where) {
generics.where_clause = self.parse_where_clause()?;
if self.eat(&token::Semi) {
// If we see a: `struct Foo<T> where T: Copy;` style decl.
VariantData::Unit(ast::DUMMY_NODE_ID)
} else {
// If we see: `struct Foo<T> where T: Copy { ... }`
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
}
// No `where` so: `struct Foo<T>;`
} else if self.eat(&token::Semi) {
VariantData::Unit(ast::DUMMY_NODE_ID)
// Record-style struct definition
} else if self.token == token::OpenDelim(token::Brace) {
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
// Tuple-style struct definition with optional where-clause.
} else if self.token == token::OpenDelim(token::Paren) {
let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::Semi)?;
body
} else {
let token_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected `where`, `{{`, `(`, or `;` after struct \
name, found `{}`", token_str)))
};
Ok((class_name, ItemKind::Struct(vdata, generics), None))
}
/// Parse union Foo { ... }
fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
let class_name = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let vdata = if self.token.is_keyword(keywords::Where) {
generics.where_clause = self.parse_where_clause()?;
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
} else if self.token == token::OpenDelim(token::Brace) {
VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
} else {
let token_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected `where` or `{{` after union \
name, found `{}`", token_str)))
};
Ok((class_name, ItemKind::Union(vdata, generics), None))
}
fn consume_block(&mut self, delim: token::DelimToken) {
let mut brace_depth = 0;
if !self.eat(&token::OpenDelim(delim)) {
return;
}
loop {
if self.eat(&token::OpenDelim(delim)) {
brace_depth += 1;
} else if self.eat(&token::CloseDelim(delim)) {
if brace_depth == 0 {
return;
} else {
brace_depth -= 1;
continue;
}
} else if self.eat(&token::Eof) || self.eat(&token::CloseDelim(token::NoDelim)) {
return;
} else {
self.bump();
}
}
}
pub fn parse_record_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
let mut fields = Vec::new();
if self.eat(&token::OpenDelim(token::Brace)) {
while self.token != token::CloseDelim(token::Brace) {
let field = self.parse_struct_decl_field().map_err(|e| {
self.recover_stmt();
e
});
match field {
Ok(field) => fields.push(field),
Err(mut err) => {
err.emit();
}
}
}
self.eat(&token::CloseDelim(token::Brace));
} else {
let token_str = self.this_token_to_string();
return Err(self.fatal(&format!("expected `where`, or `{{` after struct \
name, found `{}`",
token_str)));
}
Ok(fields)
}
pub fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
// This is the case where we find `struct Foo<T>(T) where T: Copy;`
// Unit like structs are handled in parse_item_struct function
let fields = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| {
let attrs = p.parse_outer_attributes()?;
let lo = p.span;
let vis = p.parse_visibility(true)?;
let ty = p.parse_ty()?;
Ok(StructField {
span: lo.to(p.span),
vis,
ident: None,
id: ast::DUMMY_NODE_ID,
ty,
attrs,
})
})?;
Ok(fields)
}
/// Parse a structure field declaration
pub fn parse_single_struct_field(&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute> )
-> PResult<'a, StructField> {
let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
match self.token {
token::Comma => {
self.bump();
}
token::CloseDelim(token::Brace) => {}
token::DocComment(_) => {
let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
self.bump(); // consume the doc comment
if self.eat(&token::Comma) || self.token == token::CloseDelim(token::Brace) {
err.emit();
} else {
return Err(err);
}
}
_ => return Err(self.span_fatal_help(self.span,
&format!("expected `,`, or `}}`, found `{}`", self.this_token_to_string()),
"struct fields should be separated by commas")),
}
Ok(a_var)
}
/// Parse an element of a struct definition
fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let vis = self.parse_visibility(false)?;
self.parse_single_struct_field(lo, vis, attrs)
}
/// Parse `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `pub(self)` for `pub(in self)`
/// and `pub(super)` for `pub(in super)`. If the following element can't be a tuple (i.e. it's
/// a function definition, it's not a tuple struct field) and the contents within the parens
/// isn't valid, emit a proper diagnostic.
pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
maybe_whole!(self, NtVis, |x| x);
self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
if self.is_crate_vis() {
self.bump(); // `crate`
return Ok(Visibility::Crate(self.prev_span, CrateSugar::JustCrate));
}
if !self.eat_keyword(keywords::Pub) {
return Ok(Visibility::Inherited)
}
if self.check(&token::OpenDelim(token::Paren)) {
// We don't `self.bump()` the `(` yet because this might be a struct definition where
// `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
// Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
// by the following tokens.
if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) {
// `pub(crate)`
self.bump(); // `(`
self.bump(); // `crate`
let vis = Visibility::Crate(self.prev_span, CrateSugar::PubCrate);
self.expect(&token::CloseDelim(token::Paren))?; // `)`
return Ok(vis)
} else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
// `pub(in path)`
self.bump(); // `(`
self.bump(); // `in`
let path = self.parse_path(PathStyle::Mod)?.default_to_global(); // `path`
let vis = Visibility::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
self.expect(&token::CloseDelim(token::Paren))?; // `)`
return Ok(vis)
} else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
t.is_keyword(keywords::SelfValue)) {
// `pub(self)` or `pub(super)`
self.bump(); // `(`
let path = self.parse_path(PathStyle::Mod)?.default_to_global(); // `super`/`self`
let vis = Visibility::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
self.expect(&token::CloseDelim(token::Paren))?; // `)`
return Ok(vis)
} else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
// `pub(something) fn ...` or `struct X { pub(something) y: Z }`
self.bump(); // `(`
let msg = "incorrect visibility restriction";
let suggestion = r##"some possible visibility restrictions are:
`pub(crate)`: visible only on the current crate
`pub(super)`: visible only in the current module's parent
`pub(in path::to::module)`: visible only on the specified path"##;
let path = self.parse_path(PathStyle::Mod)?;
let path_span = self.prev_span;
let help_msg = format!("make this visible only to module `{}` with `in`", path);
self.expect(&token::CloseDelim(token::Paren))?; // `)`
let mut err = self.span_fatal_help(path_span, msg, suggestion);
err.span_suggestion(path_span, &help_msg, format!("in {}", path));
err.emit(); // emit diagnostic, but continue with public visibility
}
}
Ok(Visibility::Public)
}
/// Parse defaultness: DEFAULT or nothing
fn parse_defaultness(&mut self) -> PResult<'a, Defaultness> {
if self.eat_defaultness() {
Ok(Defaultness::Default)
} else {
Ok(Defaultness::Final)
}
}
/// Given a termination token, parse all of the items in a module
fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
let mut items = vec![];
while let Some(item) = self.parse_item()? {
items.push(item);
}
if !self.eat(term) {
let token_str = self.this_token_to_string();
let mut err = self.fatal(&format!("expected item, found `{}`", token_str));
let msg = "consider removing this semicolon";
if token_str == ";" {
err.span_suggestion_short(self.span, msg, "".to_string());
}
return Err(err);
}
let hi = if self.span == syntax_pos::DUMMY_SP {
inner_lo
} else {
self.prev_span
};
Ok(ast::Mod {
inner: inner_lo.to(hi),
items,
})
}
fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
let id = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
self.expect(&token::Eq)?;
let e = self.parse_expr()?;
self.expect(&token::Semi)?;
let item = match m {
Some(m) => ItemKind::Static(ty, m, e),
None => ItemKind::Const(ty, e),
};
Ok((id, item, None))
}
/// Parse a `mod <foo> { ... }` or `mod <foo>;` item
fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
let (in_cfg, outer_attrs) = {
let mut strip_unconfigured = ::config::StripUnconfigured {
sess: self.sess,
should_test: false, // irrelevant
features: None, // don't perform gated feature checking
};
let outer_attrs = strip_unconfigured.process_cfg_attrs(outer_attrs.to_owned());
(!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
};
let id_span = self.span;
let id = self.parse_ident()?;
if self.check(&token::Semi) {
self.bump();
if in_cfg && self.recurse_into_file_modules {
// This mod is in an external file. Let's go get it!
let ModulePathSuccess { path, directory_ownership, warn } =
self.submod_path(id, &outer_attrs, id_span)?;
let (module, mut attrs) =
self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
if warn {
let attr = ast::Attribute {
id: attr::mk_attr_id(),
style: ast::AttrStyle::Outer,
path: ast::Path::from_ident(syntax_pos::DUMMY_SP,
Ident::from_str("warn_directory_ownership")),
tokens: TokenStream::empty(),
is_sugared_doc: false,
span: syntax_pos::DUMMY_SP,
};
attr::mark_known(&attr);
attrs.push(attr);
}
Ok((id, module, Some(attrs)))
} else {
let placeholder = ast::Mod { inner: syntax_pos::DUMMY_SP, items: Vec::new() };
Ok((id, ItemKind::Mod(placeholder), None))
}
} else {
let old_directory = self.directory.clone();
self.push_directory(id, &outer_attrs);
self.expect(&token::OpenDelim(token::Brace))?;
let mod_inner_lo = self.span;
let attrs = self.parse_inner_attributes()?;
let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
self.directory = old_directory;
Ok((id, ItemKind::Mod(module), Some(attrs)))
}
}
fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") {
self.directory.path.push(&path.as_str());
self.directory.ownership = DirectoryOwnership::Owned { relative: None };
} else {
self.directory.path.push(&id.name.as_str());
}
}
pub fn submod_path_from_attr(attrs: &[ast::Attribute], dir_path: &Path) -> Option<PathBuf> {
attr::first_attr_value_str_by_name(attrs, "path").map(|d| dir_path.join(&d.as_str()))
}
/// Returns either a path to a module, or .
pub fn default_submod_path(
id: ast::Ident,
relative: Option<ast::Ident>,
dir_path: &Path,
codemap: &CodeMap) -> ModulePath
{
// If we're in a foo.rs file instead of a mod.rs file,
// we need to look for submodules in
// `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
// `./<id>.rs` and `./<id>/mod.rs`.
let relative_prefix_string;
let relative_prefix = if let Some(ident) = relative {
relative_prefix_string = format!("{}{}", ident.name.as_str(), path::MAIN_SEPARATOR);
&relative_prefix_string
} else {
""
};
let mod_name = id.to_string();
let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
let secondary_path_str = format!("{}{}{}mod.rs",
relative_prefix, mod_name, path::MAIN_SEPARATOR);
let default_path = dir_path.join(&default_path_str);
let secondary_path = dir_path.join(&secondary_path_str);
let default_exists = codemap.file_exists(&default_path);
let secondary_exists = codemap.file_exists(&secondary_path);
let result = match (default_exists, secondary_exists) {
(true, false) => Ok(ModulePathSuccess {
path: default_path,
directory_ownership: DirectoryOwnership::Owned {
relative: Some(id),
},
warn: false,
}),
(false, true) => Ok(ModulePathSuccess {
path: secondary_path,
directory_ownership: DirectoryOwnership::Owned {
relative: None,
},
warn: false,
}),
(false, false) => Err(Error::FileNotFoundForModule {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
dir_path: format!("{}", dir_path.display()),
}),
(true, true) => Err(Error::DuplicatePaths {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
}),
};
ModulePath {
name: mod_name,
path_exists: default_exists || secondary_exists,
result,
}
}
fn submod_path(&mut self,
id: ast::Ident,
outer_attrs: &[ast::Attribute],
id_sp: Span)
-> PResult<'a, ModulePathSuccess> {
if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
return Ok(ModulePathSuccess {
directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
// All `#[path]` files are treated as though they are a `mod.rs` file.
// This means that `mod foo;` declarations inside `#[path]`-included
// files are siblings,
//
// Note that this will produce weirdness when a file named `foo.rs` is
// `#[path]` included and contains a `mod foo;` declaration.
// If you encounter this, it's your own darn fault :P
Some(_) => DirectoryOwnership::Owned { relative: None },
_ => DirectoryOwnership::UnownedViaMod(true),
},
path,
warn: false,
});
}
let relative = match self.directory.ownership {
DirectoryOwnership::Owned { relative } => {
// Push the usage onto the list of non-mod.rs mod uses.
// This is used later for feature-gate error reporting.
if let Some(cur_file_ident) = relative {
self.sess
.non_modrs_mods.borrow_mut()
.push((cur_file_ident, id_sp));
}
relative
},
DirectoryOwnership::UnownedViaBlock |
DirectoryOwnership::UnownedViaMod(_) => None,
};
let paths = Parser::default_submod_path(
id, relative, &self.directory.path, self.sess.codemap());
match self.directory.ownership {
DirectoryOwnership::Owned { .. } => {
paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
},
DirectoryOwnership::UnownedViaBlock => {
let msg =
"Cannot declare a non-inline module inside a block \
unless it has a path attribute";
let mut err = self.diagnostic().struct_span_err(id_sp, msg);
if paths.path_exists {
let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
paths.name);
err.span_note(id_sp, &msg);
}
Err(err)
}
DirectoryOwnership::UnownedViaMod(warn) => {
if warn {
if let Ok(result) = paths.result {
return Ok(ModulePathSuccess { warn: true, ..result });
}
}
let mut err = self.diagnostic().struct_span_err(id_sp,
"cannot declare a new module at this location");
if id_sp != syntax_pos::DUMMY_SP {
let src_path = self.sess.codemap().span_to_filename(id_sp);
if let FileName::Real(src_path) = src_path {
if let Some(stem) = src_path.file_stem() {
let mut dest_path = src_path.clone();
dest_path.set_file_name(stem);
dest_path.push("mod.rs");
err.span_note(id_sp,
&format!("maybe move this module `{}` to its own \
directory via `{}`", src_path.display(),
dest_path.display()));
}
}
}
if paths.path_exists {
err.span_note(id_sp,
&format!("... or maybe `use` the module `{}` instead \
of possibly redeclaring it",
paths.name));
}
Err(err)
}
}
}
/// Read a module from a source file.
fn eval_src_mod(&mut self,
path: PathBuf,
directory_ownership: DirectoryOwnership,
name: String,
id_sp: Span)
-> PResult<'a, (ast::ItemKind, Vec<ast::Attribute> )> {
let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
let mut err = String::from("circular modules: ");
let len = included_mod_stack.len();
for p in &included_mod_stack[i.. len] {
err.push_str(&p.to_string_lossy());
err.push_str(" -> ");
}
err.push_str(&path.to_string_lossy());
return Err(self.span_fatal(id_sp, &err[..]));
}
included_mod_stack.push(path.clone());
drop(included_mod_stack);
let mut p0 =
new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
p0.cfg_mods = self.cfg_mods;
let mod_inner_lo = p0.span;
let mod_attrs = p0.parse_inner_attributes()?;
let m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
self.sess.included_mod_stack.borrow_mut().pop();
Ok((ast::ItemKind::Mod(m0), mod_attrs))
}
/// Parse a function declaration from a foreign module
fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
self.expect_keyword(keywords::Fn)?;
let (ident, mut generics) = self.parse_fn_header()?;
let decl = self.parse_fn_decl(true)?;
generics.where_clause = self.parse_where_clause()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ast::ForeignItem {
ident,
attrs,
node: ForeignItemKind::Fn(decl, generics),
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis,
})
}
/// Parse a static item from a foreign module.
/// Assumes that the `static` keyword is already parsed.
fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
let mutbl = self.eat_keyword(keywords::Mut);
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ForeignItem {
ident,
attrs,
node: ForeignItemKind::Static(ty, mutbl),
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis,
})
}
/// Parse a type from a foreign module
fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-> PResult<'a, ForeignItem> {
self.expect_keyword(keywords::Type)?;
let ident = self.parse_ident()?;
let hi = self.span;
self.expect(&token::Semi)?;
Ok(ast::ForeignItem {
ident: ident,
attrs: attrs,
node: ForeignItemKind::Ty,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
vis: vis
})
}
/// Parse extern crate links
///
/// # Examples
///
/// extern crate foo;
/// extern crate bar as foo;
fn parse_item_extern_crate(&mut self,
lo: Span,
visibility: Visibility,
attrs: Vec<Attribute>)
-> PResult<'a, P<Item>> {
let crate_name = self.parse_ident()?;
let (maybe_path, ident) = if let Some(ident) = self.parse_rename()? {
(Some(crate_name.name), ident)
} else {
(None, crate_name)
};
self.expect(&token::Semi)?;
let prev_span = self.prev_span;
Ok(self.mk_item(lo.to(prev_span),
ident,
ItemKind::ExternCrate(maybe_path),
visibility,
attrs))
}
/// Parse `extern` for foreign ABIs
/// modules.
///
/// `extern` is expected to have been
/// consumed before calling this method
///
/// # Examples:
///
/// extern "C" {}
/// extern {}
fn parse_item_foreign_mod(&mut self,
lo: Span,
opt_abi: Option<abi::Abi>,
visibility: Visibility,
mut attrs: Vec<Attribute>)
-> PResult<'a, P<Item>> {
self.expect(&token::OpenDelim(token::Brace))?;
let abi = opt_abi.unwrap_or(Abi::C);
attrs.extend(self.parse_inner_attributes()?);
let mut foreign_items = vec![];
while let Some(item) = self.parse_foreign_item()? {
foreign_items.push(item);
}
self.expect(&token::CloseDelim(token::Brace))?;
let prev_span = self.prev_span;
let m = ast::ForeignMod {
abi,
items: foreign_items
};
let invalid = keywords::Invalid.ident();
Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
}
/// Parse type Foo = Bar;
fn parse_item_type(&mut self) -> PResult<'a, ItemInfo> {
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
tps.where_clause = self.parse_where_clause()?;
self.expect(&token::Eq)?;
let ty = self.parse_ty()?;
self.expect(&token::Semi)?;
Ok((ident, ItemKind::Ty(ty, tps), None))
}
/// Parse the part of an "enum" decl following the '{'
fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
let mut variants = Vec::new();
let mut all_nullary = true;
let mut any_disr = None;
while self.token != token::CloseDelim(token::Brace) {
let variant_attrs = self.parse_outer_attributes()?;
let vlo = self.span;
let struct_def;
let mut disr_expr = None;
let ident = self.parse_ident()?;
if self.check(&token::OpenDelim(token::Brace)) {
// Parse a struct variant.
all_nullary = false;
struct_def = VariantData::Struct(self.parse_record_struct_body()?,
ast::DUMMY_NODE_ID);
} else if self.check(&token::OpenDelim(token::Paren)) {
all_nullary = false;
struct_def = VariantData::Tuple(self.parse_tuple_struct_body()?,
ast::DUMMY_NODE_ID);
} else if self.eat(&token::Eq) {
disr_expr = Some(self.parse_expr()?);
any_disr = disr_expr.as_ref().map(|expr| expr.span);
struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
} else {
struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
}
let vr = ast::Variant_ {
name: ident,
attrs: variant_attrs,
data: struct_def,
disr_expr,
};
variants.push(respan(vlo.to(self.prev_span), vr));
if !self.eat(&token::Comma) { break; }
}
self.expect(&token::CloseDelim(token::Brace))?;
match any_disr {
Some(disr_span) if !all_nullary =>
self.span_err(disr_span,
"discriminator values can only be used with a field-less enum"),
_ => ()
}
Ok(ast::EnumDef { variants: variants })
}
/// Parse an "enum" declaration
fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
let id = self.parse_ident()?;
let mut generics = self.parse_generics()?;
generics.where_clause = self.parse_where_clause()?;
self.expect(&token::OpenDelim(token::Brace))?;
let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
self.recover_stmt();
self.eat(&token::CloseDelim(token::Brace));
e
})?;
Ok((id, ItemKind::Enum(enum_definition, generics), None))
}
/// Parses a string as an ABI spec on an extern type or module. Consumes
/// the `extern` keyword, if one is found.
fn parse_opt_abi(&mut self) -> PResult<'a, Option<abi::Abi>> {
match self.token {
token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
let sp = self.span;
self.expect_no_suffix(sp, "ABI spec", suf);
self.bump();
match abi::lookup(&s.as_str()) {
Some(abi) => Ok(Some(abi)),
None => {
let prev_span = self.prev_span;
self.span_err(
prev_span,
&format!("invalid ABI: expected one of [{}], \
found `{}`",
abi::all_names().join(", "),
s));
Ok(None)
}
}
}
_ => Ok(None),
}
}
/// Parse one of the items allowed by the flags.
/// NB: this function no longer parses the items inside an
/// extern crate.
fn parse_item_(&mut self, attrs: Vec<Attribute>,
macros_allowed: bool, attributes_allowed: bool) -> PResult<'a, Option<P<Item>>> {
maybe_whole!(self, NtItem, |item| {
let mut item = item.into_inner();
let mut attrs = attrs;
mem::swap(&mut item.attrs, &mut attrs);
item.attrs.extend(attrs);
Some(P(item))
});
let lo = self.span;
let visibility = self.parse_visibility(false)?;
if self.eat_keyword(keywords::Use) {
// USE ITEM
let item_ = ItemKind::Use(P(self.parse_use_tree(false)?));
self.expect(&token::Semi)?;
let prev_span = self.prev_span;
let invalid = keywords::Invalid.ident();
let item = self.mk_item(lo.to(prev_span), invalid, item_, visibility, attrs);
return Ok(Some(item));
}
if self.check_keyword(keywords::Extern) && self.is_extern_non_path() {
self.bump(); // `extern`
if self.eat_keyword(keywords::Crate) {
return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
}
let opt_abi = self.parse_opt_abi()?;
if self.eat_keyword(keywords::Fn) {
// EXTERN FUNCTION ITEM
let fn_span = self.prev_span;
let abi = opt_abi.unwrap_or(Abi::C);
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Normal,
respan(fn_span, Constness::NotConst),
abi)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
} else if self.check(&token::OpenDelim(token::Brace)) {
return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
}
self.unexpected()?;
}
if self.eat_keyword(keywords::Static) {
// STATIC ITEM
let m = if self.eat_keyword(keywords::Mut) {
Mutability::Mutable
} else {
Mutability::Immutable
};
let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Const) {
let const_span = self.prev_span;
if self.check_keyword(keywords::Fn)
|| (self.check_keyword(keywords::Unsafe)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
// CONST FUNCTION ITEM
let unsafety = if self.eat_keyword(keywords::Unsafe) {
Unsafety::Unsafe
} else {
Unsafety::Normal
};
self.bump();
let (ident, item_, extra_attrs) =
self.parse_item_fn(unsafety,
respan(const_span, Constness::Const),
Abi::Rust)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
// CONST ITEM
if self.eat_keyword(keywords::Mut) {
let prev_span = self.prev_span;
self.diagnostic().struct_span_err(prev_span, "const globals cannot be mutable")
.help("did you mean to declare a static?")
.emit();
}
let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Unsafe) &&
(self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
{
// UNSAFE TRAIT ITEM
self.expect_keyword(keywords::Unsafe)?;
let is_auto = if self.eat_keyword(keywords::Trait) {
IsAuto::No
} else {
self.expect_keyword(keywords::Auto)?;
self.expect_keyword(keywords::Trait)?;
IsAuto::Yes
};
let (ident, item_, extra_attrs) =
self.parse_item_trait(is_auto, ast::Unsafety::Unsafe)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if (self.check_keyword(keywords::Unsafe) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl))) ||
(self.check_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Impl)))
{
// IMPL ITEM
let defaultness = self.parse_defaultness()?;
self.expect_keyword(keywords::Unsafe)?;
self.expect_keyword(keywords::Impl)?;
let (ident,
item_,
extra_attrs) = self.parse_item_impl(ast::Unsafety::Unsafe, defaultness)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Fn) {
// FUNCTION ITEM
self.bump();
let fn_span = self.prev_span;
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Normal,
respan(fn_span, Constness::NotConst),
Abi::Rust)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Unsafe)
&& self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
// UNSAFE FUNCTION ITEM
self.bump();
let abi = if self.eat_keyword(keywords::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(keywords::Fn)?;
let fn_span = self.prev_span;
let (ident, item_, extra_attrs) =
self.parse_item_fn(Unsafety::Unsafe,
respan(fn_span, Constness::NotConst),
abi)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Mod) {
// MODULE ITEM
let (ident, item_, extra_attrs) =
self.parse_item_mod(&attrs[..])?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Type) {
// TYPE ITEM
let (ident, item_, extra_attrs) = self.parse_item_type()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Enum) {
// ENUM ITEM
let (ident, item_, extra_attrs) = self.parse_item_enum()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.check_keyword(keywords::Trait)
|| (self.check_keyword(keywords::Auto)
&& self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
{
let is_auto = if self.eat_keyword(keywords::Trait) {
IsAuto::No
} else {
self.expect_keyword(keywords::Auto)?;
self.expect_keyword(keywords::Trait)?;
IsAuto::Yes
};
// TRAIT ITEM
let (ident, item_, extra_attrs) =
self.parse_item_trait(is_auto, ast::Unsafety::Normal)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if (self.check_keyword(keywords::Impl)) ||
(self.check_keyword(keywords::Default) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Impl)))
{
// IMPL ITEM
let defaultness = self.parse_defaultness()?;
self.expect_keyword(keywords::Impl)?;
let (ident,
item_,
extra_attrs) = self.parse_item_impl(ast::Unsafety::Normal, defaultness)?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.eat_keyword(keywords::Struct) {
// STRUCT ITEM
let (ident, item_, extra_attrs) = self.parse_item_struct()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if self.is_union_item() {
// UNION ITEM
self.bump();
let (ident, item_, extra_attrs) = self.parse_item_union()?;
let prev_span = self.prev_span;
let item = self.mk_item(lo.to(prev_span),
ident,
item_,
visibility,
maybe_append(attrs, extra_attrs));
return Ok(Some(item));
}
if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
return Ok(Some(macro_def));
}
// Verify wether we have encountered a struct or method definition where the user forgot to
// add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
if visibility == Visibility::Public &&
self.check_ident() &&
self.look_ahead(1, |t| *t != token::Not)
{
// Space between `pub` keyword and the identifier
//
// pub S {}
// ^^^ `sp` points here
let sp = self.prev_span.between(self.span);
let full_sp = self.prev_span.to(self.span);
let ident_sp = self.span;
if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
// possible public struct definition where `struct` was forgotten
let ident = self.parse_ident().unwrap();
let msg = format!("add `struct` here to parse `{}` as a public struct",
ident);
let mut err = self.diagnostic()
.struct_span_err(sp, "missing `struct` for struct definition");
err.span_suggestion_short(sp, &msg, " struct ".into());
return Err(err);
} else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
let ident = self.parse_ident().unwrap();
self.consume_block(token::Paren);
let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) ||
self.check(&token::OpenDelim(token::Brace))
{
("fn", "method", false)
} else if self.check(&token::Colon) {
let kw = "struct";
(kw, kw, false)
} else {
("fn` or `struct", "method or struct", true)
};
let msg = format!("missing `{}` for {} definition", kw, kw_name);
let mut err = self.diagnostic().struct_span_err(sp, &msg);
if !ambiguous {
let suggestion = format!("add `{}` here to parse `{}` as a public {}",
kw,
ident,
kw_name);
err.span_suggestion_short(sp, &suggestion, format!(" {} ", kw));
} else {
if let Ok(snippet) = self.sess.codemap().span_to_snippet(ident_sp) {
err.span_suggestion(
full_sp,
"if you meant to call a macro, write instead",
format!("{}!", snippet));
} else {
err.help("if you meant to call a macro, remove the `pub` \
and add a trailing `!` after the identifier");
}
}
return Err(err);
}
}
self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
}
/// Parse a foreign item.
fn parse_foreign_item(&mut self) -> PResult<'a, Option<ForeignItem>> {
let attrs = self.parse_outer_attributes()?;
let lo = self.span;
let visibility = self.parse_visibility(false)?;
// FOREIGN STATIC ITEM
// Treat `const` as `static` for error recovery, but don't add it to expected tokens.
if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
if self.token.is_keyword(keywords::Const) {
self.diagnostic()
.struct_span_err(self.span, "extern items cannot be `const`")
.span_suggestion(self.span, "instead try using", "static".to_owned())
.emit();
}
self.bump(); // `static` or `const`
return Ok(Some(self.parse_item_foreign_static(visibility, lo, attrs)?));
}
// FOREIGN FUNCTION ITEM
if self.check_keyword(keywords::Fn) {
return Ok(Some(self.parse_item_foreign_fn(visibility, lo, attrs)?));
}
// FOREIGN TYPE ITEM
if self.check_keyword(keywords::Type) {
return Ok(Some(self.parse_item_foreign_type(visibility, lo, attrs)?));
}
// FIXME #5668: this will occur for a macro invocation:
match self.parse_macro_use_or_failure(attrs, true, false, lo, visibility)? {
Some(item) => {
return Err(self.span_fatal(item.span, "macros cannot expand to foreign items"));
}
None => Ok(None)
}
}
/// This is the fall-through for parsing items.
fn parse_macro_use_or_failure(
&mut self,
attrs: Vec<Attribute> ,
macros_allowed: bool,
attributes_allowed: bool,
lo: Span,
visibility: Visibility
) -> PResult<'a, Option<P<Item>>> {
if macros_allowed && self.token.is_path_start() {
// MACRO INVOCATION ITEM
let prev_span = self.prev_span;
self.complain_if_pub_macro(&visibility, prev_span);
let mac_lo = self.span;
// item macro.
let pth = self.parse_path(PathStyle::Mod)?;
self.expect(&token::Not)?;
// a 'special' identifier (like what `macro_rules!` uses)
// is optional. We should eventually unify invoc syntax
// and remove this.
let id = if self.token.is_ident() {
self.parse_ident()?
} else {
keywords::Invalid.ident() // no special identifier
};
// eat a matched-delimiter token tree:
let (delim, tts) = self.expect_delimited_token_tree()?;
if delim != token::Brace {
if !self.eat(&token::Semi) {
self.span_err(self.prev_span,
"macros that expand to items must either \
be surrounded with braces or followed by \
a semicolon");
}
}
let hi = self.prev_span;
let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts: tts });
let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
return Ok(Some(item));
}
// FAILURE TO PARSE ITEM
match visibility {
Visibility::Inherited => {}
_ => {
return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
}
}
if !attributes_allowed && !attrs.is_empty() {
self.expected_item_err(&attrs);
}
Ok(None)
}
fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
where F: FnOnce(&mut Self) -> PResult<'a, R>
{
// Record all tokens we parse when parsing this item.
let mut tokens = Vec::new();
match self.token_cursor.frame.last_token {
LastToken::Collecting(_) => {
panic!("cannot collect tokens recursively yet")
}
LastToken::Was(ref mut last) => tokens.extend(last.take()),
}
self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
let prev = self.token_cursor.stack.len();
let ret = f(self);
let last_token = if self.token_cursor.stack.len() == prev {
&mut self.token_cursor.frame.last_token
} else {
&mut self.token_cursor.stack[prev].last_token
};
let mut tokens = match *last_token {
LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
LastToken::Was(_) => panic!("our vector went away?"),
};
// If we're not at EOF our current token wasn't actually consumed by
// `f`, but it'll still be in our list that we pulled out. In that case
// put it back.
if self.token == token::Eof {
*last_token = LastToken::Was(None);
} else {
*last_token = LastToken::Was(tokens.pop());
}
Ok((ret?, tokens.into_iter().collect()))
}
pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
let attrs = self.parse_outer_attributes()?;
let (ret, tokens) = self.collect_tokens(|this| {
this.parse_item_(attrs, true, false)
})?;
// Once we've parsed an item and recorded the tokens we got while
// parsing we may want to store `tokens` into the item we're about to
// return. Note, though, that we specifically didn't capture tokens
// related to outer attributes. The `tokens` field here may later be
// used with procedural macros to convert this item back into a token
// stream, but during expansion we may be removing attributes as we go
// along.
//
// If we've got inner attributes then the `tokens` we've got above holds
// these inner attributes. If an inner attribute is expanded we won't
// actually remove it from the token stream, so we'll just keep yielding
// it (bad!). To work around this case for now we just avoid recording
// `tokens` if we detect any inner attributes. This should help keep
// expansion correct, but we should fix this bug one day!
Ok(ret.map(|item| {
item.map(|mut i| {
if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
i.tokens = Some(tokens);
}
i
})
}))
}
/// `{` or `::{` or `*` or `::*`
/// `::{` or `::*` (also `{` or `*` if unprefixed is true)
fn is_import_coupler(&mut self, unprefixed: bool) -> bool {
self.is_import_coupler_inner(&token::OpenDelim(token::Brace), unprefixed) ||
self.is_import_coupler_inner(&token::BinOp(token::Star), unprefixed)
}
fn is_import_coupler_inner(&mut self, token: &token::Token, unprefixed: bool) -> bool {
if self.check(&token::ModSep) {
self.look_ahead(1, |t| t == token)
} else if unprefixed {
self.check(token)
} else {
false
}
}
/// Parse UseTree
///
/// USE_TREE = `*` |
/// `{` USE_TREE_LIST `}` |
/// PATH `::` `*` |
/// PATH `::` `{` USE_TREE_LIST `}` |
/// PATH [`as` IDENT]
fn parse_use_tree(&mut self, nested: bool) -> PResult<'a, UseTree> {
let lo = self.span;
let mut prefix = ast::Path {
segments: vec![],
span: lo.to(self.span),
};
let kind = if self.is_import_coupler(true) {
// `use *;` or `use ::*;` or `use {...};` `use ::{...};`
// Remove the first `::`
if self.eat(&token::ModSep) {
prefix.segments.push(PathSegment::crate_root(self.prev_span));
} else if !nested {
prefix.segments.push(PathSegment::crate_root(self.span));
}
if self.eat(&token::BinOp(token::Star)) {
// `use *;`
UseTreeKind::Glob
} else if self.check(&token::OpenDelim(token::Brace)) {
// `use {...};`
UseTreeKind::Nested(self.parse_use_tree_list()?)
} else {
return self.unexpected();
}
} else {
// `use path::...;`
let mut parsed = self.parse_path(PathStyle::Mod)?;
if !nested {
parsed = parsed.default_to_global();
}
prefix.segments.append(&mut parsed.segments);
prefix.span = prefix.span.to(parsed.span);
if self.eat(&token::ModSep) {
if self.eat(&token::BinOp(token::Star)) {
// `use path::*;`
UseTreeKind::Glob
} else if self.check(&token::OpenDelim(token::Brace)) {
// `use path::{...};`
UseTreeKind::Nested(self.parse_use_tree_list()?)
} else {
return self.unexpected();
}
} else {
// `use path::foo;` or `use path::foo as bar;`
let rename = self.parse_rename()?.
unwrap_or(prefix.segments.last().unwrap().identifier);
UseTreeKind::Simple(rename)
}
};
Ok(UseTree {
span: lo.to(self.prev_span),
kind,
prefix,
})
}
/// Parse UseTreeKind::Nested(list)
///
/// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
&token::CloseDelim(token::Brace),
SeqSep::trailing_allowed(token::Comma), |this| {
Ok((this.parse_use_tree(true)?, ast::DUMMY_NODE_ID))
})
}
fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
if self.eat_keyword(keywords::As) {
self.parse_ident().map(Some)
} else {
Ok(None)
}
}
/// Parses a source module as a crate. This is the main
/// entry point for the parser.
pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
let lo = self.span;
Ok(ast::Crate {
attrs: self.parse_inner_attributes()?,
module: self.parse_mod_items(&token::Eof, lo)?,
span: lo.to(self.span),
})
}
pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
let ret = match self.token {
token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
_ => return None
};
self.bump();
Some(ret)
}
pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
match self.parse_optional_str() {
Some((s, style, suf)) => {
let sp = self.prev_span;
self.expect_no_suffix(sp, "string literal", suf);
Ok((s, style))
}
_ => Err(self.fatal("expected string literal"))
}
}
}