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fuchsia / third_party / rust / 4ce792ded6da82f57d91adb077e90352b0142a46 / . / src / librustc_parse / parser / item.rs
blob: 31db7fc5f759d086c2abafe01cfc5564d2b65297 [file] [log] [blame]
use super::diagnostics::{dummy_arg, ConsumeClosingDelim, Error};
use super::{FollowedByType, Parser, PathStyle};
use crate::maybe_whole;
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, PResult, StashKey};
use rustc_span::source_map::{self, respan, Span};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::BytePos;
use syntax::ast::{self, AttrKind, AttrStyle, AttrVec, Attribute, Ident, DUMMY_NODE_ID};
use syntax::ast::{AssocItem, AssocItemKind, Item, ItemKind, UseTree, UseTreeKind};
use syntax::ast::{BindingMode, Block, FnDecl, FnSig, Mac, MacArgs, MacDelimiter, Param, SelfKind};
use syntax::ast::{Constness, Defaultness, Extern, IsAsync, IsAuto, PathSegment, StrLit, Unsafety};
use syntax::ast::{EnumDef, Generics, StructField, TraitRef, Ty, TyKind, Variant, VariantData};
use syntax::ast::{FnHeader, ForeignItem, ForeignItemKind, Mutability, Visibility, VisibilityKind};
use syntax::print::pprust;
use syntax::ptr::P;
use syntax::token;
use syntax::tokenstream::{DelimSpan, TokenStream, TokenTree};
use log::debug;
use std::mem;
pub(super) type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
impl<'a> Parser<'a> {
pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
let attrs = self.parse_outer_attributes()?;
self.parse_item_(attrs, true, false)
}
pub(super) fn parse_item_(
&mut self,
attrs: Vec<Attribute>,
macros_allowed: bool,
attributes_allowed: bool,
) -> PResult<'a, Option<P<Item>>> {
let mut unclosed_delims = vec![];
let (ret, tokens) = self.collect_tokens(|this| {
let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
unclosed_delims.append(&mut this.unclosed_delims);
item
})?;
self.unclosed_delims.append(&mut unclosed_delims);
// 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
})
}))
}
/// Parses one of the items allowed by the flags.
fn parse_item_implementation(
&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.token.span;
let vis = self.parse_visibility(FollowedByType::No)?;
if self.eat_keyword(kw::Use) {
// USE ITEM
let item_ = ItemKind::Use(P(self.parse_use_tree()?));
self.expect_semi()?;
let span = lo.to(self.prev_span);
let item = self.mk_item(span, Ident::invalid(), item_, vis, attrs);
return Ok(Some(item));
}
if self.eat_keyword(kw::Extern) {
let extern_sp = self.prev_span;
if self.eat_keyword(kw::Crate) {
return Ok(Some(self.parse_item_extern_crate(lo, vis, attrs)?));
}
let abi = self.parse_abi();
if self.eat_keyword(kw::Fn) {
// EXTERN FUNCTION ITEM
let fn_span = self.prev_span;
let header = FnHeader {
unsafety: Unsafety::Normal,
asyncness: respan(fn_span, IsAsync::NotAsync),
constness: respan(fn_span, Constness::NotConst),
ext: Extern::from_abi(abi),
};
return self.parse_item_fn(lo, vis, attrs, header);
} else if self.check(&token::OpenDelim(token::Brace)) {
return Ok(Some(self.parse_item_foreign_mod(lo, abi, vis, attrs, extern_sp)?));
}
self.unexpected()?;
}
if self.is_static_global() {
self.bump();
// STATIC ITEM
let m = self.parse_mutability();
let info = self.parse_item_const(Some(m))?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.eat_keyword(kw::Const) {
let const_span = self.prev_span;
if [kw::Fn, kw::Unsafe, kw::Extern].iter().any(|k| self.check_keyword(*k)) {
// CONST FUNCTION ITEM
let unsafety = self.parse_unsafety();
if self.check_keyword(kw::Extern) {
self.sess.gated_spans.gate(sym::const_extern_fn, lo.to(self.token.span));
}
let ext = self.parse_extern()?;
self.expect_keyword(kw::Fn)?;
let header = FnHeader {
unsafety,
asyncness: respan(const_span, IsAsync::NotAsync),
constness: respan(const_span, Constness::Const),
ext,
};
return self.parse_item_fn(lo, vis, attrs, header);
}
// CONST ITEM
if self.eat_keyword(kw::Mut) {
let prev_span = self.prev_span;
self.struct_span_err(prev_span, "const globals cannot be mutable")
.span_label(prev_span, "cannot be mutable")
.span_suggestion(
const_span,
"you might want to declare a static instead",
"static".to_owned(),
Applicability::MaybeIncorrect,
)
.emit();
}
let info = self.parse_item_const(None)?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
// Parses `async unsafe? fn`.
if self.check_keyword(kw::Async) {
let async_span = self.token.span;
if self.is_keyword_ahead(1, &[kw::Fn]) || self.is_keyword_ahead(2, &[kw::Fn]) {
// ASYNC FUNCTION ITEM
self.bump(); // `async`
let unsafety = self.parse_unsafety(); // `unsafe`?
self.expect_keyword(kw::Fn)?; // `fn`
let fn_span = self.prev_span;
let asyncness = respan(
async_span,
IsAsync::Async {
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
},
);
self.ban_async_in_2015(async_span);
let header = FnHeader {
unsafety,
asyncness,
constness: respan(fn_span, Constness::NotConst),
ext: Extern::None,
};
return self.parse_item_fn(lo, vis, attrs, header);
}
}
if self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto]) {
// UNSAFE TRAIT ITEM
self.bump(); // `unsafe`
let info = self.parse_item_trait(lo, Unsafety::Unsafe)?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.check_keyword(kw::Impl)
|| self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
|| self.check_keyword(kw::Default) && self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe])
{
// IMPL ITEM
let defaultness = self.parse_defaultness();
let unsafety = self.parse_unsafety();
self.expect_keyword(kw::Impl)?;
let info = self.parse_item_impl(unsafety, defaultness)?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.check_keyword(kw::Fn) {
// FUNCTION ITEM
self.bump();
let fn_span = self.prev_span;
let header = FnHeader {
unsafety: Unsafety::Normal,
asyncness: respan(fn_span, IsAsync::NotAsync),
constness: respan(fn_span, Constness::NotConst),
ext: Extern::None,
};
return self.parse_item_fn(lo, vis, attrs, header);
}
if self.check_keyword(kw::Unsafe)
&& self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace))
{
// UNSAFE FUNCTION ITEM
self.bump(); // `unsafe`
// `{` is also expected after `unsafe`; in case of error, include it in the diagnostic.
self.check(&token::OpenDelim(token::Brace));
let ext = self.parse_extern()?;
self.expect_keyword(kw::Fn)?;
let fn_span = self.prev_span;
let header = FnHeader {
unsafety: Unsafety::Unsafe,
asyncness: respan(fn_span, IsAsync::NotAsync),
constness: respan(fn_span, Constness::NotConst),
ext,
};
return self.parse_item_fn(lo, vis, attrs, header);
}
if self.eat_keyword(kw::Mod) {
// MODULE ITEM
let info = self.parse_item_mod(&attrs[..])?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.eat_keyword(kw::Type) {
// TYPE ITEM
let (ident, ty, generics) = self.parse_type_alias()?;
let kind = ItemKind::TyAlias(ty, generics);
return self.mk_item_with_info(attrs, lo, vis, (ident, kind, None));
}
if self.eat_keyword(kw::Enum) {
// ENUM ITEM
let info = self.parse_item_enum()?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.check_keyword(kw::Trait)
|| (self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait]))
{
// TRAIT ITEM
let info = self.parse_item_trait(lo, Unsafety::Normal)?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.eat_keyword(kw::Struct) {
// STRUCT ITEM
let info = self.parse_item_struct()?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if self.is_union_item() {
// UNION ITEM
self.bump();
let info = self.parse_item_union()?;
return self.mk_item_with_info(attrs, lo, vis, info);
}
if let Some(macro_def) = self.eat_macro_def(&attrs, &vis, lo)? {
return Ok(Some(macro_def));
}
// Verify whether 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 vis.node.is_pub() && 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.token.span);
let full_sp = self.prev_span.to(self.token.span);
let ident_sp = self.token.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.struct_span_err(sp, "missing `struct` for struct definition");
err.span_suggestion_short(
sp,
&msg,
" struct ".into(),
Applicability::MaybeIncorrect, // speculative
);
return Err(err);
} else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
let ident = self.parse_ident().unwrap();
self.bump(); // `(`
let kw_name = self.recover_first_param();
self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
self.bump(); // `{`
("fn", kw_name, false)
} else if self.check(&token::OpenDelim(token::Brace)) {
self.bump(); // `{`
("fn", kw_name, false)
} else if self.check(&token::Colon) {
let kw = "struct";
(kw, kw, false)
} else {
("fn` or `struct", "function or struct", true)
};
let msg = format!("missing `{}` for {} definition", kw, kw_name);
let mut err = self.struct_span_err(sp, &msg);
if !ambiguous {
self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
let suggestion =
format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name);
err.span_suggestion_short(
sp,
&suggestion,
format!(" {} ", kw),
Applicability::MachineApplicable,
);
} else {
if let Ok(snippet) = self.span_to_snippet(ident_sp) {
err.span_suggestion(
full_sp,
"if you meant to call a macro, try",
format!("{}!", snippet),
// this is the `ambiguous` conditional branch
Applicability::MaybeIncorrect,
);
} else {
err.help(
"if you meant to call a macro, remove the `pub` \
and add a trailing `!` after the identifier",
);
}
}
return Err(err);
} else if self.look_ahead(1, |t| *t == token::Lt) {
let ident = self.parse_ident().unwrap();
self.eat_to_tokens(&[&token::Gt]);
self.bump(); // `>`
let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
("fn", self.recover_first_param(), false)
} else if self.check(&token::OpenDelim(token::Brace)) {
("struct", "struct", false)
} else {
("fn` or `struct", "function or struct", true)
};
let msg = format!("missing `{}` for {} definition", kw, kw_name);
let mut err = self.struct_span_err(sp, &msg);
if !ambiguous {
err.span_suggestion_short(
sp,
&format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
format!(" {} ", kw),
Applicability::MachineApplicable,
);
}
return Err(err);
}
}
self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, vis)
}
pub(super) fn mk_item_with_info(
&self,
attrs: Vec<Attribute>,
lo: Span,
vis: Visibility,
info: ItemInfo,
) -> PResult<'a, Option<P<Item>>> {
let (ident, item, extra_attrs) = info;
let span = lo.to(self.prev_span);
let attrs = Self::maybe_append(attrs, extra_attrs);
Ok(Some(self.mk_item(span, ident, item, vis, attrs)))
}
fn maybe_append<T>(mut lhs: Vec<T>, mut rhs: Option<Vec<T>>) -> Vec<T> {
if let Some(ref mut rhs) = rhs {
lhs.append(rhs);
}
lhs
}
/// 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()
&& !(self.is_async_fn() && self.token.span.rust_2015())
{
// MACRO INVOCATION ITEM
let prev_span = self.prev_span;
self.complain_if_pub_macro(&visibility.node, prev_span);
// Item macro
let path = self.parse_path(PathStyle::Mod)?;
self.expect(&token::Not)?;
let args = self.parse_mac_args()?;
if args.need_semicolon() && !self.eat(&token::Semi) {
self.report_invalid_macro_expansion_item();
}
let hi = self.prev_span;
let mac = Mac { path, args, prior_type_ascription: self.last_type_ascription };
let item =
self.mk_item(lo.to(hi), Ident::invalid(), ItemKind::Mac(mac), visibility, attrs);
return Ok(Some(item));
}
// FAILURE TO PARSE ITEM
match visibility.node {
VisibilityKind::Inherited => {}
_ => return Err(self.struct_span_err(self.prev_span, "unmatched visibility `pub`")),
}
if !attributes_allowed && !attrs.is_empty() {
self.expected_item_err(&attrs)?;
}
Ok(None)
}
/// Emits an expected-item-after-attributes error.
fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
let message = match attrs.last() {
Some(&Attribute { kind: AttrKind::DocComment(_), .. }) => {
"expected item after doc comment"
}
_ => "expected item after attributes",
};
let mut err = self.struct_span_err(self.prev_span, message);
if attrs.last().unwrap().is_doc_comment() {
err.span_label(self.prev_span, "this doc comment doesn't document anything");
}
Err(err)
}
pub(super) fn is_async_fn(&self) -> bool {
self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
}
/// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
fn parse_assoc_macro_invoc(
&mut self,
item_kind: &str,
vis: Option<&Visibility>,
at_end: &mut bool,
) -> PResult<'a, Option<Mac>> {
if self.token.is_path_start() && !(self.is_async_fn() && self.token.span.rust_2015()) {
let prev_span = self.prev_span;
let path = self.parse_path(PathStyle::Mod)?;
if path.segments.len() == 1 {
if !self.eat(&token::Not) {
return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
}
} else {
self.expect(&token::Not)?;
}
if let Some(vis) = vis {
self.complain_if_pub_macro(&vis.node, prev_span);
}
*at_end = true;
// eat a matched-delimiter token tree:
let args = self.parse_mac_args()?;
if args.need_semicolon() {
self.expect_semi()?;
}
Ok(Some(Mac { path, args, prior_type_ascription: self.last_type_ascription }))
} else {
Ok(None)
}
}
fn missing_assoc_item_kind_err(
&self,
item_type: &str,
prev_span: Span,
) -> DiagnosticBuilder<'a> {
let expected_kinds = if item_type == "extern" {
"missing `fn`, `type`, or `static`"
} else {
"missing `fn`, `type`, or `const`"
};
// 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
.struct_span_err(sp, &format!("{} for {}-item declaration", expected_kinds, item_type));
err.span_label(sp, expected_kinds);
err
}
/// Parses an implementation item, `impl` keyword is already parsed.
///
/// impl<'a, T> TYPE { /* impl items */ }
/// impl<'a, T> TRAIT for TYPE { /* impl items */ }
/// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
/// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
///
/// We actually parse slightly more relaxed grammar for better error reporting and recovery.
/// `impl` GENERICS `const`? `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
/// `impl` GENERICS `const`? `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
fn parse_item_impl(
&mut self,
unsafety: Unsafety,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
// First, parse generic parameters if necessary.
let mut generics = if self.choose_generics_over_qpath() {
self.parse_generics()?
} else {
let mut generics = Generics::default();
// impl A for B {}
// /\ this is where `generics.span` should point when there are no type params.
generics.span = self.prev_span.shrink_to_hi();
generics
};
let constness = if self.eat_keyword(kw::Const) {
let span = self.prev_span;
self.sess.gated_spans.gate(sym::const_trait_impl, span);
Constness::Const
} else {
Constness::NotConst
};
// Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
self.bump(); // `!`
ast::ImplPolarity::Negative
} else {
ast::ImplPolarity::Positive
};
// Parse both types and traits as a type, then reinterpret if necessary.
let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
{
let span = self.prev_span.between(self.token.span);
self.struct_span_err(span, "missing trait in a trait impl").emit();
P(Ty { kind: TyKind::Path(None, err_path(span)), span, id: DUMMY_NODE_ID })
} else {
self.parse_ty()?
};
// If `for` is missing we try to recover.
let has_for = self.eat_keyword(kw::For);
let missing_for_span = self.prev_span.between(self.token.span);
let ty_second = if self.token == token::DotDot {
// We need to report this error after `cfg` expansion for compatibility reasons
self.bump(); // `..`, do not add it to expected tokens
Some(self.mk_ty(self.prev_span, TyKind::Err))
} else if has_for || self.token.can_begin_type() {
Some(self.parse_ty()?)
} else {
None
};
generics.where_clause = self.parse_where_clause()?;
let (impl_items, attrs) = self.parse_impl_body()?;
let item_kind = match ty_second {
Some(ty_second) => {
// impl Trait for Type
if !has_for {
self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
.span_suggestion_short(
missing_for_span,
"add `for` here",
" for ".to_string(),
Applicability::MachineApplicable,
)
.emit();
}
let ty_first = ty_first.into_inner();
let path = match ty_first.kind {
// This notably includes paths passed through `ty` macro fragments (#46438).
TyKind::Path(None, path) => path,
_ => {
self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
err_path(ty_first.span)
}
};
let trait_ref = TraitRef { path, ref_id: ty_first.id };
ItemKind::Impl {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: Some(trait_ref),
self_ty: ty_second,
items: impl_items,
}
}
None => {
// impl Type
ItemKind::Impl {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: None,
self_ty: ty_first,
items: impl_items,
}
}
};
Ok((Ident::invalid(), item_kind, Some(attrs)))
}
fn parse_impl_body(&mut self) -> PResult<'a, (Vec<AssocItem>, Vec<Attribute>)> {
self.expect(&token::OpenDelim(token::Brace))?;
let attrs = self.parse_inner_attributes()?;
let mut impl_items = Vec::new();
while !self.eat(&token::CloseDelim(token::Brace)) {
let mut at_end = false;
match self.parse_impl_item(&mut at_end) {
Ok(impl_item) => impl_items.push(impl_item),
Err(mut err) => {
err.emit();
if !at_end {
self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
break;
}
}
}
}
Ok((impl_items, attrs))
}
/// Parses defaultness (i.e., `default` or nothing).
fn parse_defaultness(&mut self) -> Defaultness {
// `pub` is included for better error messages
if self.check_keyword(kw::Default)
&& self.is_keyword_ahead(
1,
&[
kw::Impl,
kw::Const,
kw::Async,
kw::Fn,
kw::Unsafe,
kw::Extern,
kw::Type,
kw::Pub,
],
)
{
self.bump(); // `default`
Defaultness::Default
} else {
Defaultness::Final
}
}
/// Parses `auto? trait Foo { ... }` or `trait Foo = Bar;`.
fn parse_item_trait(&mut self, lo: Span, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
// Parse optional `auto` prefix.
let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
self.expect_keyword(kw::Trait)?;
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
// Parse optional colon and supertrait bounds.
let had_colon = self.eat(&token::Colon);
let span_at_colon = self.prev_span;
let bounds =
if had_colon { self.parse_generic_bounds(Some(self.prev_span))? } else { Vec::new() };
let span_before_eq = self.prev_span;
if self.eat(&token::Eq) {
// It's a trait alias.
if had_colon {
let span = span_at_colon.to(span_before_eq);
self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
}
let bounds = self.parse_generic_bounds(None)?;
tps.where_clause = self.parse_where_clause()?;
self.expect_semi()?;
let whole_span = lo.to(self.prev_span);
if is_auto == IsAuto::Yes {
let msg = "trait aliases cannot be `auto`";
self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
}
if unsafety != Unsafety::Normal {
let msg = "trait aliases cannot be `unsafe`";
self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
}
self.sess.gated_spans.gate(sym::trait_alias, whole_span);
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)) {
if let token::DocComment(_) = self.token.kind {
if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
struct_span_err!(
self.diagnostic(),
self.token.span,
E0584,
"found a documentation comment that doesn't document anything",
)
.help(
"doc comments must come before what they document, maybe a \
comment was intended with `//`?",
)
.emit();
self.bump();
continue;
}
}
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.consume_block(token::Brace, ConsumeClosingDelim::Yes);
break;
}
}
}
}
Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
}
}
pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, AssocItem> {
maybe_whole!(self, NtImplItem, |x| x);
self.parse_assoc_item(at_end, |_| true)
}
pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, AssocItem> {
maybe_whole!(self, NtTraitItem, |x| x);
// This is somewhat dubious; We don't want to allow
// param names to be left off if there is a definition...
//
// We don't allow param names to be left off in edition 2018.
self.parse_assoc_item(at_end, |t| t.span.rust_2018())
}
/// Parses associated items.
fn parse_assoc_item(
&mut self,
at_end: &mut bool,
is_name_required: fn(&token::Token) -> bool,
) -> PResult<'a, AssocItem> {
let attrs = self.parse_outer_attributes()?;
let mut unclosed_delims = vec![];
let (mut item, tokens) = self.collect_tokens(|this| {
let item = this.parse_assoc_item_(at_end, attrs, is_name_required);
unclosed_delims.append(&mut this.unclosed_delims);
item
})?;
self.unclosed_delims.append(&mut unclosed_delims);
// 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_assoc_item_(
&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>,
is_name_required: fn(&token::Token) -> bool,
) -> PResult<'a, AssocItem> {
let lo = self.token.span;
let vis = self.parse_visibility(FollowedByType::No)?;
let defaultness = self.parse_defaultness();
let (name, kind, generics) = if self.eat_keyword(kw::Type) {
self.parse_assoc_ty()?
} else if self.is_const_item() {
self.parse_assoc_const()?
} else if let Some(mac) = self.parse_assoc_macro_invoc("associated", Some(&vis), at_end)? {
(Ident::invalid(), AssocItemKind::Macro(mac), Generics::default())
} else {
self.parse_assoc_fn(at_end, &mut attrs, is_name_required)?
};
Ok(AssocItem {
id: DUMMY_NODE_ID,
span: lo.to(self.prev_span),
ident: name,
attrs,
vis,
defaultness,
generics,
kind,
tokens: None,
})
}
/// Returns `true` if we are looking at `const ID`
/// (returns `false` for things like `const fn`, etc.).
fn is_const_item(&self) -> bool {
self.token.is_keyword(kw::Const) && !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
}
/// This parses the grammar:
///
/// AssocConst = "const" Ident ":" Ty "=" Expr ";"
fn parse_assoc_const(&mut self) -> PResult<'a, (Ident, AssocItemKind, Generics)> {
self.expect_keyword(kw::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
self.expect_semi()?;
Ok((ident, AssocItemKind::Const(ty, expr), Generics::default()))
}
/// Parses the following grammar:
///
/// AssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
fn parse_assoc_ty(&mut self) -> PResult<'a, (Ident, AssocItemKind, Generics)> {
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_generic_bounds(None)? } 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_semi()?;
Ok((ident, AssocItemKind::TyAlias(bounds, default), generics))
}
/// Parses a `UseTree`.
///
/// ```
/// USE_TREE = [`::`] `*` |
/// [`::`] `{` USE_TREE_LIST `}` |
/// PATH `::` `*` |
/// PATH `::` `{` USE_TREE_LIST `}` |
/// PATH [`as` IDENT]
/// ```
fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
let lo = self.token.span;
let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
let kind = if self.check(&token::OpenDelim(token::Brace))
|| self.check(&token::BinOp(token::Star))
|| self.is_import_coupler()
{
// `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
let mod_sep_ctxt = self.token.span.ctxt();
if self.eat(&token::ModSep) {
prefix
.segments
.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
}
self.parse_use_tree_glob_or_nested()?
} else {
// `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
prefix = self.parse_path(PathStyle::Mod)?;
if self.eat(&token::ModSep) {
self.parse_use_tree_glob_or_nested()?
} else {
UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
}
};
Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
}
/// Parses `*` or `{...}`.
fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
Ok(if self.eat(&token::BinOp(token::Star)) {
UseTreeKind::Glob
} else {
UseTreeKind::Nested(self.parse_use_tree_list()?)
})
}
/// Parses a `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_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
.map(|(r, _)| r)
}
fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
}
fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
match self.token.kind {
token::Ident(name, false) if name == kw::Underscore => {
let span = self.token.span;
self.bump();
Ok(Ident::new(name, span))
}
_ => self.parse_ident(),
}
}
/// Parses `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>> {
// Accept `extern crate name-like-this` for better diagnostics
let orig_name = self.parse_crate_name_with_dashes()?;
let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
(rename, Some(orig_name.name))
} else {
(orig_name, None)
};
self.expect_semi()?;
let span = lo.to(self.prev_span);
Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
}
fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
let error_msg = "crate name using dashes are not valid in `extern crate` statements";
let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
in the code";
let mut ident = if self.token.is_keyword(kw::SelfLower) {
self.parse_path_segment_ident()
} else {
self.parse_ident()
}?;
let mut idents = vec![];
let mut replacement = vec![];
let mut fixed_crate_name = false;
// Accept `extern crate name-like-this` for better diagnostics.
let dash = token::BinOp(token::BinOpToken::Minus);
if self.token == dash {
// Do not include `-` as part of the expected tokens list.
while self.eat(&dash) {
fixed_crate_name = true;
replacement.push((self.prev_span, "_".to_string()));
idents.push(self.parse_ident()?);
}
}
if fixed_crate_name {
let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
let mut fixed_name = format!("{}", ident.name);
for part in idents {
fixed_name.push_str(&format!("_{}", part.name));
}
ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
self.struct_span_err(fixed_name_sp, error_msg)
.span_label(fixed_name_sp, "dash-separated idents are not valid")
.multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
.emit();
}
Ok(ident)
}
/// Parses `extern` for foreign ABIs modules.
///
/// `extern` is expected to have been
/// consumed before calling this method.
///
/// # Examples
///
/// ```ignore (only-for-syntax-highlight)
/// extern "C" {}
/// extern {}
/// ```
fn parse_item_foreign_mod(
&mut self,
lo: Span,
abi: Option<StrLit>,
visibility: Visibility,
mut attrs: Vec<Attribute>,
extern_sp: Span,
) -> PResult<'a, P<Item>> {
self.expect(&token::OpenDelim(token::Brace))?;
attrs.extend(self.parse_inner_attributes()?);
let mut foreign_items = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
foreign_items.push(self.parse_foreign_item(extern_sp)?);
}
let prev_span = self.prev_span;
let m = ast::ForeignMod { abi, items: foreign_items };
let invalid = Ident::invalid();
Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
}
/// Parses a foreign item.
pub fn parse_foreign_item(&mut self, extern_sp: Span) -> PResult<'a, ForeignItem> {
maybe_whole!(self, NtForeignItem, |ni| ni);
let attrs = self.parse_outer_attributes()?;
let lo = self.token.span;
let visibility = self.parse_visibility(FollowedByType::No)?;
// FOREIGN STATIC ITEM
// Treat `const` as `static` for error recovery, but don't add it to expected tokens.
if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
if self.token.is_keyword(kw::Const) {
let mut err =
self.struct_span_err(self.token.span, "extern items cannot be `const`");
// The user wrote 'const fn'
if self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe]) {
err.emit();
// Consume `const`
self.bump();
// Consume `unsafe` if present, since `extern` blocks
// don't allow it. This will leave behind a plain 'fn'
self.eat_keyword(kw::Unsafe);
// Treat 'const fn` as a plain `fn` for error recovery purposes.
// We've already emitted an error, so compilation is guaranteed
// to fail
return Ok(self.parse_item_foreign_fn(visibility, lo, attrs, extern_sp)?);
}
err.span_suggestion(
self.token.span,
"try using a static value",
"static".to_owned(),
Applicability::MachineApplicable,
);
err.emit();
}
self.bump(); // `static` or `const`
return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
}
// FOREIGN FUNCTION ITEM
if self.check_keyword(kw::Fn) {
return Ok(self.parse_item_foreign_fn(visibility, lo, attrs, extern_sp)?);
}
// FOREIGN TYPE ITEM
if self.check_keyword(kw::Type) {
return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
}
match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
Some(mac) => Ok(ForeignItem {
ident: Ident::invalid(),
span: lo.to(self.prev_span),
id: DUMMY_NODE_ID,
attrs,
vis: visibility,
kind: ForeignItemKind::Macro(mac),
tokens: None,
}),
None => {
if !attrs.is_empty() {
self.expected_item_err(&attrs)?;
}
self.unexpected()
}
}
}
/// Parses 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.parse_mutability();
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let hi = self.token.span;
self.expect_semi()?;
Ok(ForeignItem {
ident,
attrs,
kind: ForeignItemKind::Static(ty, mutbl),
id: DUMMY_NODE_ID,
span: lo.to(hi),
vis,
tokens: None,
})
}
/// Parses 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(kw::Type)?;
let ident = self.parse_ident()?;
let hi = self.token.span;
self.expect_semi()?;
Ok(ast::ForeignItem {
ident,
attrs,
kind: ForeignItemKind::Ty,
id: DUMMY_NODE_ID,
span: lo.to(hi),
vis,
tokens: None,
})
}
fn is_static_global(&mut self) -> bool {
if self.check_keyword(kw::Static) {
// Check if this could be a closure.
!self.look_ahead(1, |token| {
if token.is_keyword(kw::Move) {
return true;
}
match token.kind {
token::BinOp(token::Or) | token::OrOr => true,
_ => false,
}
})
} else {
false
}
}
/// Parse `["const" | ("static" "mut"?)] $ident ":" $ty = $expr` with
/// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
///
/// When `m` is `"const"`, `$ident` may also be `"_"`.
fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
// Parse the type of a `const` or `static mut?` item.
// That is, the `":" $ty` fragment.
let ty = if self.token == token::Eq {
self.recover_missing_const_type(id, m)
} else {
// Not `=` so expect `":"" $ty` as usual.
self.expect(&token::Colon)?;
self.parse_ty()?
};
self.expect(&token::Eq)?;
let e = self.parse_expr()?;
self.expect_semi()?;
let item = match m {
Some(m) => ItemKind::Static(ty, m, e),
None => ItemKind::Const(ty, e),
};
Ok((id, item, None))
}
/// We were supposed to parse `:` but instead, we're already at `=`.
/// This means that the type is missing.
fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
// Construct the error and stash it away with the hope
// that typeck will later enrich the error with a type.
let kind = match m {
Some(Mutability::Mut) => "static mut",
Some(Mutability::Not) => "static",
None => "const",
};
let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
err.span_suggestion(
id.span,
"provide a type for the item",
format!("{}: <type>", id),
Applicability::HasPlaceholders,
);
err.stash(id.span, StashKey::ItemNoType);
// The user intended that the type be inferred,
// so treat this as if the user wrote e.g. `const A: _ = expr;`.
P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID })
}
/// Parses the grammar:
/// Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
fn parse_type_alias(&mut self) -> PResult<'a, (Ident, P<Ty>, Generics)> {
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_semi()?;
Ok((ident, ty, tps))
}
/// Parses 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()?;
let (variants, _) =
self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
self.recover_stmt();
e
})?;
let enum_definition =
EnumDef { variants: variants.into_iter().filter_map(|v| v).collect() };
Ok((id, ItemKind::Enum(enum_definition, generics), None))
}
fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
let variant_attrs = self.parse_outer_attributes()?;
let vlo = self.token.span;
let vis = self.parse_visibility(FollowedByType::No)?;
if !self.recover_nested_adt_item(kw::Enum)? {
return Ok(None);
}
let ident = self.parse_ident()?;
let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
// Parse a struct variant.
let (fields, recovered) = self.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
} else if self.check(&token::OpenDelim(token::Paren)) {
VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID)
} else {
VariantData::Unit(DUMMY_NODE_ID)
};
let disr_expr =
if self.eat(&token::Eq) { Some(self.parse_anon_const_expr()?) } else { None };
let vr = ast::Variant {
ident,
vis,
id: DUMMY_NODE_ID,
attrs: variant_attrs,
data: struct_def,
disr_expr,
span: vlo.to(self.prev_span),
is_placeholder: false,
};
Ok(Some(vr))
}
/// Parses `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(kw::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(DUMMY_NODE_ID)
} else {
// If we see: `struct Foo<T> where T: Copy { ... }`
let (fields, recovered) = self.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
}
// No `where` so: `struct Foo<T>;`
} else if self.eat(&token::Semi) {
VariantData::Unit(DUMMY_NODE_ID)
// Record-style struct definition
} else if self.token == token::OpenDelim(token::Brace) {
let (fields, recovered) = self.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
// 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()?, DUMMY_NODE_ID);
generics.where_clause = self.parse_where_clause()?;
self.expect_semi()?;
body
} else {
let token_str = super::token_descr(&self.token);
let msg = &format!(
"expected `where`, `{{`, `(`, or `;` after struct name, found {}",
token_str
);
let mut err = self.struct_span_err(self.token.span, msg);
err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
return Err(err);
};
Ok((class_name, ItemKind::Struct(vdata, generics), None))
}
/// Parses `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(kw::Where) {
generics.where_clause = self.parse_where_clause()?;
let (fields, recovered) = self.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
} else if self.token == token::OpenDelim(token::Brace) {
let (fields, recovered) = self.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
} else {
let token_str = super::token_descr(&self.token);
let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
let mut err = self.struct_span_err(self.token.span, msg);
err.span_label(self.token.span, "expected `where` or `{` after union name");
return Err(err);
};
Ok((class_name, ItemKind::Union(vdata, generics), None))
}
pub(super) fn is_union_item(&self) -> bool {
self.token.is_keyword(kw::Union)
&& self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
}
fn parse_record_struct_body(
&mut self,
) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
let mut fields = Vec::new();
let mut recovered = false;
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.consume_block(token::Brace, ConsumeClosingDelim::No);
recovered = true;
e
});
match field {
Ok(field) => fields.push(field),
Err(mut err) => {
err.emit();
break;
}
}
}
self.eat(&token::CloseDelim(token::Brace));
} else {
let token_str = super::token_descr(&self.token);
let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
let mut err = self.struct_span_err(self.token.span, msg);
err.span_label(self.token.span, "expected `where`, or `{` after struct name");
return Err(err);
}
Ok((fields, recovered))
}
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
self.parse_paren_comma_seq(|p| {
let attrs = p.parse_outer_attributes()?;
let lo = p.token.span;
let vis = p.parse_visibility(FollowedByType::Yes)?;
let ty = p.parse_ty()?;
Ok(StructField {
span: lo.to(ty.span),
vis,
ident: None,
id: DUMMY_NODE_ID,
ty,
attrs,
is_placeholder: false,
})
})
.map(|(r, _)| r)
}
/// Parses an element of a struct declaration.
fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
let attrs = self.parse_outer_attributes()?;
let lo = self.token.span;
let vis = self.parse_visibility(FollowedByType::No)?;
self.parse_single_struct_field(lo, vis, attrs)
}
/// Parses a structure field declaration.
fn parse_single_struct_field(
&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute>,
) -> PResult<'a, StructField> {
let mut seen_comma: bool = false;
let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
if self.token == token::Comma {
seen_comma = true;
}
match self.token.kind {
token::Comma => {
self.bump();
}
token::CloseDelim(token::Brace) => {}
token::DocComment(_) => {
let previous_span = self.prev_span;
let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
self.bump(); // consume the doc comment
let comma_after_doc_seen = self.eat(&token::Comma);
// `seen_comma` is always false, because we are inside doc block
// condition is here to make code more readable
if seen_comma == false && comma_after_doc_seen == true {
seen_comma = true;
}
if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
err.emit();
} else {
if seen_comma == false {
let sp = self.sess.source_map().next_point(previous_span);
err.span_suggestion(
sp,
"missing comma here",
",".into(),
Applicability::MachineApplicable,
);
}
return Err(err);
}
}
_ => {
let sp = self.prev_span.shrink_to_hi();
let mut err = self.struct_span_err(
sp,
&format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
);
if self.token.is_ident() {
// This is likely another field; emit the diagnostic and keep going
err.span_suggestion(
sp,
"try adding a comma",
",".into(),
Applicability::MachineApplicable,
);
err.emit();
} else {
return Err(err);
}
}
}
Ok(a_var)
}
/// Parses 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: DUMMY_NODE_ID,
ty,
attrs,
is_placeholder: false,
})
}
pub(super) fn eat_macro_def(
&mut self,
attrs: &[Attribute],
vis: &Visibility,
lo: Span,
) -> PResult<'a, Option<P<Item>>> {
let (ident, def) = if self.eat_keyword(kw::Macro) {
let ident = self.parse_ident()?;
let body = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_mac_args()?
} else if self.check(&token::OpenDelim(token::Paren)) {
let params = self.parse_token_tree();
let pspan = params.span();
let body = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_token_tree()
} else {
return self.unexpected();
};
let bspan = body.span();
let tokens = TokenStream::new(vec![
params.into(),
TokenTree::token(token::FatArrow, pspan.between(bspan)).into(),
body.into(),
]);
let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
} else {
return self.unexpected();
};
(ident, ast::MacroDef { body, legacy: false })
} else if self.check_keyword(sym::macro_rules)
&& self.look_ahead(1, |t| *t == token::Not)
&& self.look_ahead(2, |t| t.is_ident())
{
let prev_span = self.prev_span;
self.complain_if_pub_macro(&vis.node, prev_span);
self.bump();
self.bump();
let ident = self.parse_ident()?;
let body = self.parse_mac_args()?;
if body.need_semicolon() && !self.eat(&token::Semi) {
self.report_invalid_macro_expansion_item();
}
(ident, ast::MacroDef { body, legacy: true })
} else {
return Ok(None);
};
let span = lo.to(self.prev_span);
if !def.legacy {
self.sess.gated_spans.gate(sym::decl_macro, span);
}
Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
}
fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
match *vis {
VisibilityKind::Inherited => {}
_ => {
let mut err = if self.token.is_keyword(sym::macro_rules) {
let mut err =
self.struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
err.span_suggestion(
sp,
"try exporting the macro",
"#[macro_export]".to_owned(),
Applicability::MaybeIncorrect, // speculative
);
err
} else {
let mut err =
self.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.emit();
}
}
}
fn report_invalid_macro_expansion_item(&self) {
let has_close_delim = self
.sess
.source_map()
.span_to_snippet(self.prev_span)
.map(|s| s.ends_with(")") || s.ends_with("]"))
.unwrap_or(false);
let right_brace_span = if has_close_delim {
// it's safe to peel off one character only when it has the close delim
self.prev_span.with_lo(self.prev_span.hi() - BytePos(1))
} else {
self.prev_span.shrink_to_hi()
};
self.struct_span_err(
self.prev_span,
"macros that expand to items must be delimited with braces or followed by a semicolon",
)
.multipart_suggestion(
"change the delimiters to curly braces",
vec![
(self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), "{".to_string()),
(right_brace_span, '}'.to_string()),
],
Applicability::MaybeIncorrect,
)
.span_suggestion(
self.prev_span.shrink_to_hi(),
"add a semicolon",
';'.to_string(),
Applicability::MaybeIncorrect,
)
.emit();
}
/// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
/// it is, we try to parse the item and report error about nested types.
fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
if (self.token.is_keyword(kw::Enum)
|| self.token.is_keyword(kw::Struct)
|| self.token.is_keyword(kw::Union))
&& self.look_ahead(1, |t| t.is_ident())
{
let kw_token = self.token.clone();
let kw_str = pprust::token_to_string(&kw_token);
let item = self.parse_item()?;
self.struct_span_err(
kw_token.span,
&format!("`{}` definition cannot be nested inside `{}`", kw_str, keyword),
)
.span_suggestion(
item.unwrap().span,
&format!("consider creating a new `{}` definition instead of nesting", kw_str),
String::new(),
Applicability::MaybeIncorrect,
)
.emit();
// We successfully parsed the item but we must inform the caller about nested problem.
return Ok(false);
}
Ok(true)
}
fn mk_item(
&self,
span: Span,
ident: Ident,
kind: ItemKind,
vis: Visibility,
attrs: Vec<Attribute>,
) -> P<Item> {
P(Item { ident, attrs, id: DUMMY_NODE_ID, kind, vis, span, tokens: None })
}
}
/// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
pub(super) struct ParamCfg {
/// Is `self` is allowed as the first parameter?
pub is_self_allowed: bool,
/// `is_name_required` decides if, per-parameter,
/// the parameter must have a pattern or just a type.
pub is_name_required: fn(&token::Token) -> bool,
}
/// Parsing of functions and methods.
impl<'a> Parser<'a> {
/// Parses an item-position function declaration.
fn parse_item_fn(
&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute>,
header: FnHeader,
) -> PResult<'a, Option<P<Item>>> {
let (ident, decl, generics) =
self.parse_fn_sig(ParamCfg { is_self_allowed: false, is_name_required: |_| true })?;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
let kind = ItemKind::Fn(FnSig { decl, header }, generics, body);
self.mk_item_with_info(attrs, lo, vis, (ident, kind, Some(inner_attrs)))
}
/// Parses a function declaration from a foreign module.
fn parse_item_foreign_fn(
&mut self,
vis: ast::Visibility,
lo: Span,
attrs: Vec<Attribute>,
extern_sp: Span,
) -> PResult<'a, ForeignItem> {
self.expect_keyword(kw::Fn)?;
let (ident, decl, generics) =
self.parse_fn_sig(ParamCfg { is_self_allowed: false, is_name_required: |_| true })?;
let span = lo.to(self.token.span);
self.parse_semi_or_incorrect_foreign_fn_body(&ident, extern_sp)?;
Ok(ast::ForeignItem {
ident,
attrs,
kind: ForeignItemKind::Fn(decl, generics),
id: DUMMY_NODE_ID,
span,
vis,
tokens: None,
})
}
fn parse_assoc_fn(
&mut self,
at_end: &mut bool,
attrs: &mut Vec<Attribute>,
is_name_required: fn(&token::Token) -> bool,
) -> PResult<'a, (Ident, AssocItemKind, Generics)> {
let header = self.parse_fn_front_matter()?;
let (ident, decl, generics) =
self.parse_fn_sig(ParamCfg { is_self_allowed: true, is_name_required })?;
let sig = FnSig { header, decl };
let body = self.parse_assoc_fn_body(at_end, attrs)?;
Ok((ident, AssocItemKind::Fn(sig, body), generics))
}
/// Parse the "body" of a method in an associated item definition.
/// This can either be `;` when there's no body,
/// or e.g. a block when the method is a provided one.
fn parse_assoc_fn_body(
&mut self,
at_end: &mut bool,
attrs: &mut Vec<Attribute>,
) -> PResult<'a, Option<P<Block>>> {
Ok(match self.token.kind {
token::Semi => {
debug!("parse_assoc_fn_body(): parsing required method");
self.bump();
*at_end = true;
None
}
token::OpenDelim(token::Brace) => {
debug!("parse_assoc_fn_body(): parsing provided method");
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
token::Interpolated(ref nt) => match **nt {
token::NtBlock(..) => {
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
_ => return self.expected_semi_or_open_brace(),
},
_ => return self.expected_semi_or_open_brace(),
})
}
/// 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.
fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
let is_const_fn = self.eat_keyword(kw::Const);
let const_span = self.prev_span;
let asyncness = self.parse_asyncness();
if let IsAsync::Async { .. } = asyncness {
self.ban_async_in_2015(self.prev_span);
}
let asyncness = respan(self.prev_span, asyncness);
let unsafety = self.parse_unsafety();
let (constness, unsafety, ext) = if is_const_fn {
(respan(const_span, Constness::Const), unsafety, Extern::None)
} else {
let ext = self.parse_extern()?;
(respan(self.prev_span, Constness::NotConst), unsafety, ext)
};
if !self.eat_keyword(kw::Fn) {
// It is possible for `expect_one_of` to recover given the contents of
// `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
// account for this.
if !self.expect_one_of(&[], &[])? {
unreachable!()
}
}
Ok(FnHeader { constness, unsafety, asyncness, ext })
}
/// Parse the "signature", including the identifier, parameters, and generics of a function.
fn parse_fn_sig(&mut self, cfg: ParamCfg) -> PResult<'a, (Ident, P<FnDecl>, Generics)> {
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let decl = self.parse_fn_decl(cfg, true)?;
generics.where_clause = self.parse_where_clause()?;
Ok((ident, decl, generics))
}
/// Parses the parameter list and result type of a function declaration.
pub(super) fn parse_fn_decl(
&mut self,
cfg: ParamCfg,
ret_allow_plus: bool,
) -> PResult<'a, P<FnDecl>> {
Ok(P(FnDecl {
inputs: self.parse_fn_params(cfg)?,
output: self.parse_ret_ty(ret_allow_plus, true)?,
}))
}
/// Parses the parameter list of a function, including the `(` and `)` delimiters.
fn parse_fn_params(&mut self, mut cfg: ParamCfg) -> PResult<'a, Vec<Param>> {
let is_trait_item = cfg.is_self_allowed;
// Parse the arguments, starting out with `self` being possibly allowed...
let (mut params, _) = self.parse_paren_comma_seq(|p| {
let param = p.parse_param_general(&cfg, is_trait_item).or_else(|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 (issue #34264).
Ok(dummy_arg(Ident::new(kw::Invalid, lo.to(p.prev_span))))
});
// ...now that we've parsed the first argument, `self` is no longer allowed.
cfg.is_self_allowed = false;
param
})?;
// Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
self.deduplicate_recovered_params_names(&mut params);
Ok(params)
}
/// Skips unexpected attributes and doc comments in this position and emits an appropriate
/// error.
/// This version of parse param doesn't necessarily require identifier names.
fn parse_param_general(&mut self, cfg: &ParamCfg, is_trait_item: bool) -> PResult<'a, Param> {
let lo = self.token.span;
let attrs = self.parse_outer_attributes()?;
// Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
if let Some(mut param) = self.parse_self_param()? {
param.attrs = attrs.into();
return if cfg.is_self_allowed {
Ok(param)
} else {
self.recover_bad_self_param(param, is_trait_item)
};
}
let is_name_required = match self.token.kind {
token::DotDotDot => false,
_ => (cfg.is_name_required)(&self.token),
};
let (pat, ty) = if is_name_required || self.is_named_param() {
debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
let pat = self.parse_fn_param_pat()?;
if let Err(mut err) = self.expect(&token::Colon) {
return if let Some(ident) = self.parameter_without_type(
&mut err,
pat,
is_name_required,
cfg.is_self_allowed,
is_trait_item,
) {
err.emit();
Ok(dummy_arg(ident))
} else {
Err(err)
};
}
self.eat_incorrect_doc_comment_for_param_type();
(pat, self.parse_ty_for_param()?)
} else {
debug!("parse_param_general ident_to_pat");
let parser_snapshot_before_ty = self.clone();
self.eat_incorrect_doc_comment_for_param_type();
let mut ty = self.parse_ty_for_param();
if ty.is_ok()
&& self.token != token::Comma
&& self.token != token::CloseDelim(token::Paren)
{
// This wasn't actually a type, but a pattern looking like a type,
// so we are going to rollback and re-parse for recovery.
ty = self.unexpected();
}
match ty {
Ok(ty) => {
let ident = Ident::new(kw::Invalid, self.prev_span);
let bm = BindingMode::ByValue(Mutability::Not);
let pat = self.mk_pat_ident(ty.span, bm, ident);
(pat, ty)
}
// If this is a C-variadic argument and we hit an error, return the error.
Err(err) if self.token == token::DotDotDot => return Err(err),
// Recover from attempting to parse the argument as a type without pattern.
Err(mut err) => {
err.cancel();
mem::replace(self, parser_snapshot_before_ty);
self.recover_arg_parse()?
}
}
};
let span = lo.to(self.token.span);
Ok(Param {
attrs: attrs.into(),
id: ast::DUMMY_NODE_ID,
is_placeholder: false,
pat,
span,
ty,
})
}
/// Returns the parsed optional self parameter and whether a self shortcut was used.
///
/// See `parse_self_param_with_attrs` to collect attributes.
fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
// Extract an identifier *after* having confirmed that the token is one.
let expect_self_ident = |this: &mut Self| {
match this.token.kind {
// Preserve hygienic context.
token::Ident(name, _) => {
let span = this.token.span;
this.bump();
Ident::new(name, span)
}
_ => unreachable!(),
}
};
// Is `self` `n` tokens ahead?
let is_isolated_self = |this: &Self, n| {
this.is_keyword_ahead(n, &[kw::SelfLower])
&& this.look_ahead(n + 1, |t| t != &token::ModSep)
};
// Is `mut self` `n` tokens ahead?
let is_isolated_mut_self =
|this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
// Parse `self` or `self: TYPE`. We already know the current token is `self`.
let parse_self_possibly_typed = |this: &mut Self, m| {
let eself_ident = expect_self_ident(this);
let eself_hi = this.prev_span;
let eself = if this.eat(&token::Colon) {
SelfKind::Explicit(this.parse_ty()?, m)
} else {
SelfKind::Value(m)
};
Ok((eself, eself_ident, eself_hi))
};
// Recover for the grammar `*self`, `*const self`, and `*mut self`.
let recover_self_ptr = |this: &mut Self| {
let msg = "cannot pass `self` by raw pointer";
let span = this.token.span;
this.struct_span_err(span, msg).span_label(span, msg).emit();
Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_span))
};
// 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.token.span;
let (eself, eself_ident, eself_hi) = match self.token.kind {
token::BinOp(token::And) => {
let eself = if is_isolated_self(self, 1) {
// `&self`
self.bump();
SelfKind::Region(None, Mutability::Not)
} else if is_isolated_mut_self(self, 1) {
// `&mut self`
self.bump();
self.bump();
SelfKind::Region(None, Mutability::Mut)
} else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
// `&'lt self`
self.bump();
let lt = self.expect_lifetime();
SelfKind::Region(Some(lt), Mutability::Not)
} else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
// `&'lt mut self`
self.bump();
let lt = self.expect_lifetime();
self.bump();
SelfKind::Region(Some(lt), Mutability::Mut)
} else {
// `&not_self`
return Ok(None);
};
(eself, expect_self_ident(self), self.prev_span)
}
// `*self`
token::BinOp(token::Star) if is_isolated_self(self, 1) => {
self.bump();
recover_self_ptr(self)?
}
// `*mut self` and `*const self`
token::BinOp(token::Star)
if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
{
self.bump();
self.bump();
recover_self_ptr(self)?
}
// `self` and `self: TYPE`
token::Ident(..) if is_isolated_self(self, 0) => {
parse_self_possibly_typed(self, Mutability::Not)?
}
// `mut self` and `mut self: TYPE`
token::Ident(..) if is_isolated_mut_self(self, 0) => {
self.bump();
parse_self_possibly_typed(self, Mutability::Mut)?
}
_ => return Ok(None),
};
let eself = source_map::respan(eself_lo.to(eself_hi), eself);
Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
}
fn is_named_param(&self) -> bool {
let offset = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
_ => 0,
},
token::BinOp(token::And) | token::AndAnd => 1,
_ if self.token.is_keyword(kw::Mut) => 1,
_ => 0,
};
self.look_ahead(offset, |t| t.is_ident())
&& self.look_ahead(offset + 1, |t| t == &token::Colon)
}
fn recover_first_param(&mut self) -> &'static str {
match self
.parse_outer_attributes()
.and_then(|_| self.parse_self_param())
.map_err(|mut e| e.cancel())
{
Ok(Some(_)) => "method",
_ => "function",
}
}
}