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fuchsia / third_party / rust / 6e1d94708a0a4a35ca7e46c6cac98adf62fe800e / . / compiler / rustc_parse / src / parser / item.rs
blob: df6996dbc458bfb0837ed95b1bddf94f22a35ff3 [file] [log] [blame]
use super::diagnostics::{dummy_arg, ConsumeClosingDelim};
use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
use super::{
AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, Trailing, TrailingToken,
};
use crate::errors::{self, MacroExpandsToAdtField};
use crate::fluent_generated as fluent;
use crate::maybe_whole;
use ast::token::IdentIsRaw;
use rustc_ast::ast::*;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
use rustc_ast::util::case::Case;
use rustc_ast::{self as ast};
use rustc_ast_pretty::pprust;
use rustc_errors::{codes::*, struct_span_code_err, Applicability, PResult, StashKey};
use rustc_span::edit_distance::edit_distance;
use rustc_span::edition::Edition;
use rustc_span::source_map;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{Span, DUMMY_SP};
use std::fmt::Write;
use std::mem;
use thin_vec::{thin_vec, ThinVec};
impl<'a> Parser<'a> {
/// 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, ast::Crate> {
let (attrs, items, spans) = self.parse_mod(&token::Eof)?;
Ok(ast::Crate { attrs, items, spans, id: DUMMY_NODE_ID, is_placeholder: false })
}
/// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
fn parse_item_mod(&mut self, attrs: &mut AttrVec) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety(Case::Sensitive);
self.expect_keyword(kw::Mod)?;
let id = self.parse_ident()?;
let mod_kind = if self.eat(&token::Semi) {
ModKind::Unloaded
} else {
self.expect(&token::OpenDelim(Delimiter::Brace))?;
let (inner_attrs, items, inner_span) =
self.parse_mod(&token::CloseDelim(Delimiter::Brace))?;
attrs.extend(inner_attrs);
ModKind::Loaded(items, Inline::Yes, inner_span)
};
Ok((id, ItemKind::Mod(unsafety, mod_kind)))
}
/// Parses the contents of a module (inner attributes followed by module items).
pub fn parse_mod(
&mut self,
term: &TokenKind,
) -> PResult<'a, (AttrVec, ThinVec<P<Item>>, ModSpans)> {
let lo = self.token.span;
let attrs = self.parse_inner_attributes()?;
let post_attr_lo = self.token.span;
let mut items = ThinVec::new();
while let Some(item) = self.parse_item(ForceCollect::No)? {
items.push(item);
self.maybe_consume_incorrect_semicolon(&items);
}
if !self.eat(term) {
let token_str = super::token_descr(&self.token);
if !self.maybe_consume_incorrect_semicolon(&items) {
let msg = format!("expected item, found {token_str}");
let mut err = self.dcx().struct_span_err(self.token.span, msg);
let span = self.token.span;
if self.is_kw_followed_by_ident(kw::Let) {
err.span_label(
span,
"consider using `const` or `static` instead of `let` for global variables",
);
} else {
err.span_label(span, "expected item")
.note("for a full list of items that can appear in modules, see <https://doc.rust-lang.org/reference/items.html>");
};
return Err(err);
}
}
let inject_use_span = post_attr_lo.data().with_hi(post_attr_lo.lo());
let mod_spans = ModSpans { inner_span: lo.to(self.prev_token.span), inject_use_span };
Ok((attrs, items, mod_spans))
}
}
pub(super) type ItemInfo = (Ident, ItemKind);
impl<'a> Parser<'a> {
pub fn parse_item(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<P<Item>>> {
let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
self.parse_item_(fn_parse_mode, force_collect).map(|i| i.map(P))
}
fn parse_item_(
&mut self,
fn_parse_mode: FnParseMode,
force_collect: ForceCollect,
) -> PResult<'a, Option<Item>> {
self.recover_diff_marker();
let attrs = self.parse_outer_attributes()?;
self.recover_diff_marker();
self.parse_item_common(attrs, true, false, fn_parse_mode, force_collect)
}
pub(super) fn parse_item_common(
&mut self,
attrs: AttrWrapper,
mac_allowed: bool,
attrs_allowed: bool,
fn_parse_mode: FnParseMode,
force_collect: ForceCollect,
) -> PResult<'a, Option<Item>> {
maybe_whole!(self, NtItem, |item| {
attrs.prepend_to_nt_inner(&mut item.attrs);
Some(item.into_inner())
});
let item =
self.collect_tokens_trailing_token(attrs, force_collect, |this: &mut Self, attrs| {
let item =
this.parse_item_common_(attrs, mac_allowed, attrs_allowed, fn_parse_mode);
Ok((item?, TrailingToken::None))
})?;
Ok(item)
}
fn parse_item_common_(
&mut self,
mut attrs: AttrVec,
mac_allowed: bool,
attrs_allowed: bool,
fn_parse_mode: FnParseMode,
) -> PResult<'a, Option<Item>> {
let lo = self.token.span;
let vis = self.parse_visibility(FollowedByType::No)?;
let mut def = self.parse_defaultness();
let kind = self.parse_item_kind(
&mut attrs,
mac_allowed,
lo,
&vis,
&mut def,
fn_parse_mode,
Case::Sensitive,
)?;
if let Some((ident, kind)) = kind {
self.error_on_unconsumed_default(def, &kind);
let span = lo.to(self.prev_token.span);
let id = DUMMY_NODE_ID;
let item = Item { ident, attrs, id, kind, vis, span, tokens: None };
return Ok(Some(item));
}
// At this point, we have failed to parse an item.
if !matches!(vis.kind, VisibilityKind::Inherited) {
self.dcx().emit_err(errors::VisibilityNotFollowedByItem { span: vis.span, vis });
}
if let Defaultness::Default(span) = def {
self.dcx().emit_err(errors::DefaultNotFollowedByItem { span });
}
if !attrs_allowed {
self.recover_attrs_no_item(&attrs)?;
}
Ok(None)
}
/// Error in-case `default` was parsed in an in-appropriate context.
fn error_on_unconsumed_default(&self, def: Defaultness, kind: &ItemKind) {
if let Defaultness::Default(span) = def {
self.dcx().emit_err(errors::InappropriateDefault {
span,
article: kind.article(),
descr: kind.descr(),
});
}
}
/// Parses one of the items allowed by the flags.
fn parse_item_kind(
&mut self,
attrs: &mut AttrVec,
macros_allowed: bool,
lo: Span,
vis: &Visibility,
def: &mut Defaultness,
fn_parse_mode: FnParseMode,
case: Case,
) -> PResult<'a, Option<ItemInfo>> {
let def_final = def == &Defaultness::Final;
let mut def_ = || mem::replace(def, Defaultness::Final);
let info = if self.eat_keyword_case(kw::Use, case) {
self.parse_use_item()?
} else if self.check_fn_front_matter(def_final, case) {
// FUNCTION ITEM
let (ident, sig, generics, body) =
self.parse_fn(attrs, fn_parse_mode, lo, vis, case)?;
(ident, ItemKind::Fn(Box::new(Fn { defaultness: def_(), sig, generics, body })))
} else if self.eat_keyword(kw::Extern) {
if self.eat_keyword(kw::Crate) {
// EXTERN CRATE
self.parse_item_extern_crate()?
} else {
// EXTERN BLOCK
self.parse_item_foreign_mod(attrs, Unsafe::No)?
}
} else if self.is_unsafe_foreign_mod() {
// EXTERN BLOCK
let unsafety = self.parse_unsafety(Case::Sensitive);
self.expect_keyword(kw::Extern)?;
self.parse_item_foreign_mod(attrs, unsafety)?
} else if self.is_static_global() {
// STATIC ITEM
self.bump(); // `static`
let mutability = self.parse_mutability();
let (ident, item) = self.parse_static_item(mutability)?;
(ident, ItemKind::Static(Box::new(item)))
} else if let Const::Yes(const_span) = self.parse_constness(Case::Sensitive) {
// CONST ITEM
if self.token.is_keyword(kw::Impl) {
// recover from `const impl`, suggest `impl const`
self.recover_const_impl(const_span, attrs, def_())?
} else {
self.recover_const_mut(const_span);
let (ident, generics, ty, expr) = self.parse_const_item()?;
(
ident,
ItemKind::Const(Box::new(ConstItem {
defaultness: def_(),
generics,
ty,
expr,
})),
)
}
} else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
// TRAIT ITEM
self.parse_item_trait(attrs, lo)?
} else if self.check_keyword(kw::Impl)
|| self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
{
// IMPL ITEM
self.parse_item_impl(attrs, def_())?
} else if self.is_reuse_path_item() {
self.parse_item_delegation()?
} else if self.check_keyword(kw::Mod)
|| self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
{
// MODULE ITEM
self.parse_item_mod(attrs)?
} else if self.eat_keyword(kw::Type) {
// TYPE ITEM
self.parse_type_alias(def_())?
} else if self.eat_keyword(kw::Enum) {
// ENUM ITEM
self.parse_item_enum()?
} else if self.eat_keyword(kw::Struct) {
// STRUCT ITEM
self.parse_item_struct()?
} else if self.is_kw_followed_by_ident(kw::Union) {
// UNION ITEM
self.bump(); // `union`
self.parse_item_union()?
} else if self.is_builtin() {
// BUILTIN# ITEM
return self.parse_item_builtin();
} else if self.eat_keyword(kw::Macro) {
// MACROS 2.0 ITEM
self.parse_item_decl_macro(lo)?
} else if let IsMacroRulesItem::Yes { has_bang } = self.is_macro_rules_item() {
// MACRO_RULES ITEM
self.parse_item_macro_rules(vis, has_bang)?
} else if self.isnt_macro_invocation()
&& (self.token.is_ident_named(sym::import)
|| self.token.is_ident_named(sym::using)
|| self.token.is_ident_named(sym::include)
|| self.token.is_ident_named(sym::require))
{
return self.recover_import_as_use();
} else if self.isnt_macro_invocation() && vis.kind.is_pub() {
self.recover_missing_kw_before_item()?;
return Ok(None);
} else if self.isnt_macro_invocation() && case == Case::Sensitive {
_ = def_;
// Recover wrong cased keywords
return self.parse_item_kind(
attrs,
macros_allowed,
lo,
vis,
def,
fn_parse_mode,
Case::Insensitive,
);
} else if macros_allowed && self.check_path() {
// MACRO INVOCATION ITEM
(Ident::empty(), ItemKind::MacCall(P(self.parse_item_macro(vis)?)))
} else {
return Ok(None);
};
Ok(Some(info))
}
fn recover_import_as_use(&mut self) -> PResult<'a, Option<(Ident, ItemKind)>> {
let span = self.token.span;
let token_name = super::token_descr(&self.token);
let snapshot = self.create_snapshot_for_diagnostic();
self.bump();
match self.parse_use_item() {
Ok(u) => {
self.dcx().emit_err(errors::RecoverImportAsUse { span, token_name });
Ok(Some(u))
}
Err(e) => {
e.cancel();
self.restore_snapshot(snapshot);
Ok(None)
}
}
}
fn parse_use_item(&mut self) -> PResult<'a, (Ident, ItemKind)> {
let tree = self.parse_use_tree()?;
if let Err(mut e) = self.expect_semi() {
match tree.kind {
UseTreeKind::Glob => {
e.note("the wildcard token must be last on the path");
}
UseTreeKind::Nested { .. } => {
e.note("glob-like brace syntax must be last on the path");
}
_ => (),
}
return Err(e);
}
Ok((Ident::empty(), ItemKind::Use(tree)))
}
/// When parsing a statement, would the start of a path be an item?
pub(super) fn is_path_start_item(&mut self) -> bool {
self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
|| self.is_reuse_path_item()
|| self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
|| self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
|| matches!(self.is_macro_rules_item(), IsMacroRulesItem::Yes{..}) // no: `macro_rules::b`, yes: `macro_rules! mac`
}
fn is_reuse_path_item(&mut self) -> bool {
// no: `reuse ::path` for compatibility reasons with macro invocations
self.token.is_keyword(kw::Reuse)
&& self.look_ahead(1, |t| t.is_path_start() && t.kind != token::PathSep)
}
/// Are we sure this could not possibly be a macro invocation?
fn isnt_macro_invocation(&mut self) -> bool {
self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::PathSep)
}
/// Recover on encountering a struct or method definition where the user
/// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
// Space between `pub` keyword and the identifier
//
// pub S {}
// ^^^ `sp` points here
let sp = self.prev_token.span.between(self.token.span);
let full_sp = self.prev_token.span.to(self.token.span);
let ident_sp = self.token.span;
let ident = if self.look_ahead(1, |t| {
[
token::Lt,
token::OpenDelim(Delimiter::Brace),
token::OpenDelim(Delimiter::Parenthesis),
]
.contains(&t.kind)
}) {
self.parse_ident().unwrap()
} else {
return Ok(());
};
let mut found_generics = false;
if self.check(&token::Lt) {
found_generics = true;
self.eat_to_tokens(&[&token::Gt]);
self.bump(); // `>`
}
let err = if self.check(&token::OpenDelim(Delimiter::Brace)) {
// possible public struct definition where `struct` was forgotten
Some(errors::MissingKeywordForItemDefinition::Struct { span: sp, ident })
} else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
// possible public function or tuple struct definition where `fn`/`struct` was
// forgotten
self.bump(); // `(`
let is_method = self.recover_self_param();
self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::Yes);
let err =
if self.check(&token::RArrow) || self.check(&token::OpenDelim(Delimiter::Brace)) {
self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
self.bump(); // `{`
self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
if is_method {
errors::MissingKeywordForItemDefinition::Method { span: sp, ident }
} else {
errors::MissingKeywordForItemDefinition::Function { span: sp, ident }
}
} else if self.check(&token::Semi) {
errors::MissingKeywordForItemDefinition::Struct { span: sp, ident }
} else {
errors::MissingKeywordForItemDefinition::Ambiguous {
span: sp,
subdiag: if found_generics {
None
} else if let Ok(snippet) = self.span_to_snippet(ident_sp) {
Some(errors::AmbiguousMissingKwForItemSub::SuggestMacro {
span: full_sp,
snippet,
})
} else {
Some(errors::AmbiguousMissingKwForItemSub::HelpMacro)
},
}
};
Some(err)
} else if found_generics {
Some(errors::MissingKeywordForItemDefinition::Ambiguous { span: sp, subdiag: None })
} else {
None
};
if let Some(err) = err { Err(self.dcx().create_err(err)) } else { Ok(()) }
}
fn parse_item_builtin(&mut self) -> PResult<'a, Option<ItemInfo>> {
// To be expanded
return Ok(None);
}
/// Parses an item macro, e.g., `item!();`.
fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, MacCall> {
let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
self.expect(&token::Not)?; // `!`
match self.parse_delim_args() {
// `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
Ok(args) => {
self.eat_semi_for_macro_if_needed(&args);
self.complain_if_pub_macro(vis, false);
Ok(MacCall { path, args })
}
Err(mut err) => {
// Maybe the user misspelled `macro_rules` (issue #91227)
if self.token.is_ident()
&& path.segments.len() == 1
&& edit_distance("macro_rules", &path.segments[0].ident.to_string(), 2)
.is_some()
{
err.span_suggestion(
path.span,
"perhaps you meant to define a macro",
"macro_rules",
Applicability::MachineApplicable,
);
}
Err(err)
}
}
}
/// Recover if we parsed attributes and expected an item but there was none.
fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
let ([start @ end] | [start, .., end]) = attrs else {
return Ok(());
};
let msg = if end.is_doc_comment() {
"expected item after doc comment"
} else {
"expected item after attributes"
};
let mut err = self.dcx().struct_span_err(end.span, msg);
if end.is_doc_comment() {
err.span_label(end.span, "this doc comment doesn't document anything");
} else if self.token.kind == TokenKind::Semi {
err.span_suggestion_verbose(
self.token.span,
"consider removing this semicolon",
"",
Applicability::MaybeIncorrect,
);
}
if let [.., penultimate, _] = attrs {
err.span_label(start.span.to(penultimate.span), "other attributes here");
}
Err(err)
}
fn is_async_fn(&self) -> bool {
self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
}
fn parse_polarity(&mut self) -> ast::ImplPolarity {
// Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
self.bump(); // `!`
ast::ImplPolarity::Negative(self.prev_token.span)
} else {
ast::ImplPolarity::Positive
}
}
/// Parses an implementation item.
///
/// ```ignore (illustrative)
/// 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.
/// ```ebnf
/// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
/// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
/// ```
fn parse_item_impl(
&mut self,
attrs: &mut AttrVec,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety(Case::Sensitive);
self.expect_keyword(kw::Impl)?;
// First, parse generic parameters if necessary.
let mut generics = if self.choose_generics_over_qpath(0) {
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_token.span.shrink_to_hi();
generics
};
let constness = self.parse_constness(Case::Sensitive);
if let Const::Yes(span) = constness {
self.psess.gated_spans.gate(sym::const_trait_impl, span);
}
// Parse stray `impl async Trait`
if (self.token.uninterpolated_span().at_least_rust_2018()
&& self.token.is_keyword(kw::Async))
|| self.is_kw_followed_by_ident(kw::Async)
{
self.bump();
self.dcx().emit_err(errors::AsyncImpl { span: self.prev_token.span });
}
let polarity = self.parse_polarity();
// Parse both types and traits as a type, then reinterpret if necessary.
let err_path = |span| ast::Path::from_ident(Ident::new(kw::Empty, span));
let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
{
let span = self.prev_token.span.between(self.token.span);
self.dcx().emit_err(errors::MissingTraitInTraitImpl {
span,
for_span: span.to(self.token.span),
});
P(Ty {
kind: TyKind::Path(None, err_path(span)),
span,
id: DUMMY_NODE_ID,
tokens: None,
})
} else {
self.parse_ty_with_generics_recovery(&generics)?
};
// If `for` is missing we try to recover.
let has_for = self.eat_keyword(kw::For);
let missing_for_span = self.prev_token.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
// AST validation later detects this `TyKind::Dummy` and emits an
// error. (#121072 will hopefully remove all this special handling
// of the obsolete `impl Trait for ..` and then this can go away.)
Some(self.mk_ty(self.prev_token.span, TyKind::Dummy))
} 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 = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
let item_kind = match ty_second {
Some(ty_second) => {
// impl Trait for Type
if !has_for {
self.dcx().emit_err(errors::MissingForInTraitImpl { span: missing_for_span });
}
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,
other => {
if let TyKind::ImplTrait(_, bounds, None) = other
&& let [bound] = bounds.as_slice()
{
// Suggest removing extra `impl` keyword:
// `impl<T: Default> impl Default for Wrapper<T>`
// ^^^^^
let extra_impl_kw = ty_first.span.until(bound.span());
self.dcx().emit_err(errors::ExtraImplKeywordInTraitImpl {
extra_impl_kw,
impl_trait_span: ty_first.span,
});
} else {
self.dcx().emit_err(errors::ExpectedTraitInTraitImplFoundType {
span: ty_first.span,
});
}
err_path(ty_first.span)
}
};
let trait_ref = TraitRef { path, ref_id: ty_first.id };
ItemKind::Impl(Box::new(Impl {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: Some(trait_ref),
self_ty: ty_second,
items: impl_items,
}))
}
None => {
// impl Type
ItemKind::Impl(Box::new(Impl {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: None,
self_ty: ty_first,
items: impl_items,
}))
}
};
Ok((Ident::empty(), item_kind))
}
fn parse_item_delegation(&mut self) -> PResult<'a, ItemInfo> {
let span = self.token.span;
self.expect_keyword(kw::Reuse)?;
let (qself, path) = if self.eat_lt() {
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
(None, self.parse_path(PathStyle::Expr)?)
};
let rename = if self.eat_keyword(kw::As) { Some(self.parse_ident()?) } else { None };
let body = if self.check(&token::OpenDelim(Delimiter::Brace)) {
Some(self.parse_block()?)
} else {
self.expect(&token::Semi)?;
None
};
let span = span.to(self.prev_token.span);
self.psess.gated_spans.gate(sym::fn_delegation, span);
let ident = rename.unwrap_or_else(|| path.segments.last().unwrap().ident);
let deleg = Delegation { id: DUMMY_NODE_ID, qself, path, rename, body };
Ok((ident, ItemKind::Delegation(Box::new(deleg))))
}
fn parse_item_list<T>(
&mut self,
attrs: &mut AttrVec,
mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
) -> PResult<'a, ThinVec<T>> {
let open_brace_span = self.token.span;
// Recover `impl Ty;` instead of `impl Ty {}`
if self.token == TokenKind::Semi {
self.dcx().emit_err(errors::UseEmptyBlockNotSemi { span: self.token.span });
self.bump();
return Ok(ThinVec::new());
}
self.expect(&token::OpenDelim(Delimiter::Brace))?;
attrs.extend(self.parse_inner_attributes()?);
let mut items = ThinVec::new();
while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
if self.recover_doc_comment_before_brace() {
continue;
}
self.recover_diff_marker();
match parse_item(self) {
Ok(None) => {
let mut is_unnecessary_semicolon = !items.is_empty()
// When the close delim is `)` in a case like the following, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
// but the actual `token.kind` is `token::CloseDelim(Delimiter::Brace)`.
// This is because the `token.kind` of the close delim is treated as the same as
// that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
// Therefore, `token.kind` should not be compared here.
//
// issue-60075.rs
// ```
// trait T {
// fn qux() -> Option<usize> {
// let _ = if true {
// });
// ^ this close delim
// Some(4)
// }
// ```
&& self
.span_to_snippet(self.prev_token.span)
.is_ok_and(|snippet| snippet == "}")
&& self.token.kind == token::Semi;
let mut semicolon_span = self.token.span;
if !is_unnecessary_semicolon {
// #105369, Detect spurious `;` before assoc fn body
is_unnecessary_semicolon = self.token == token::OpenDelim(Delimiter::Brace)
&& self.prev_token.kind == token::Semi;
semicolon_span = self.prev_token.span;
}
// We have to bail or we'll potentially never make progress.
let non_item_span = self.token.span;
let is_let = self.token.is_keyword(kw::Let);
let mut err =
self.dcx().struct_span_err(non_item_span, "non-item in item list");
self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
if is_let {
err.span_suggestion(
non_item_span,
"consider using `const` instead of `let` for associated const",
"const",
Applicability::MachineApplicable,
);
} else {
err.span_label(open_brace_span, "item list starts here")
.span_label(non_item_span, "non-item starts here")
.span_label(self.prev_token.span, "item list ends here");
}
if is_unnecessary_semicolon {
err.span_suggestion(
semicolon_span,
"consider removing this semicolon",
"",
Applicability::MaybeIncorrect,
);
}
err.emit();
break;
}
Ok(Some(item)) => items.extend(item),
Err(err) => {
self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
err.with_span_label(
open_brace_span,
"while parsing this item list starting here",
)
.with_span_label(self.prev_token.span, "the item list ends here")
.emit();
break;
}
}
}
Ok(items)
}
/// Recover on a doc comment before `}`.
fn recover_doc_comment_before_brace(&mut self) -> bool {
if let token::DocComment(..) = self.token.kind {
if self.look_ahead(1, |tok| tok == &token::CloseDelim(Delimiter::Brace)) {
// FIXME: merge with `DocCommentDoesNotDocumentAnything` (E0585)
struct_span_code_err!(
self.dcx(),
self.token.span,
E0584,
"found a documentation comment that doesn't document anything",
)
.with_span_label(self.token.span, "this doc comment doesn't document anything")
.with_help(
"doc comments must come before what they document, if a comment was \
intended use `//`",
)
.emit();
self.bump();
return true;
}
}
false
}
/// Parses defaultness (i.e., `default` or nothing).
fn parse_defaultness(&mut self) -> Defaultness {
// We are interested in `default` followed by another identifier.
// However, we must avoid keywords that occur as binary operators.
// Currently, the only applicable keyword is `as` (`default as Ty`).
if self.check_keyword(kw::Default)
&& self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
{
self.bump(); // `default`
Defaultness::Default(self.prev_token.uninterpolated_span())
} else {
Defaultness::Final
}
}
/// Is this an `(unsafe auto? | auto) trait` item?
fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
// auto trait
self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
// unsafe auto trait
|| self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
}
/// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
fn parse_item_trait(&mut self, attrs: &mut AttrVec, lo: Span) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety(Case::Sensitive);
// Parse optional `auto` prefix.
let is_auto = if self.eat_keyword(kw::Auto) {
self.psess.gated_spans.gate(sym::auto_traits, self.prev_token.span);
IsAuto::Yes
} else {
IsAuto::No
};
self.expect_keyword(kw::Trait)?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
// Parse optional colon and supertrait bounds.
let had_colon = self.eat(&token::Colon);
let span_at_colon = self.prev_token.span;
let bounds = if had_colon { self.parse_generic_bounds()? } else { Vec::new() };
let span_before_eq = self.prev_token.span;
if self.eat(&token::Eq) {
// It's a trait alias.
if had_colon {
let span = span_at_colon.to(span_before_eq);
self.dcx().emit_err(errors::BoundsNotAllowedOnTraitAliases { span });
}
let bounds = self.parse_generic_bounds()?;
generics.where_clause = self.parse_where_clause()?;
self.expect_semi()?;
let whole_span = lo.to(self.prev_token.span);
if is_auto == IsAuto::Yes {
self.dcx().emit_err(errors::TraitAliasCannotBeAuto { span: whole_span });
}
if let Unsafe::Yes(_) = unsafety {
self.dcx().emit_err(errors::TraitAliasCannotBeUnsafe { span: whole_span });
}
self.psess.gated_spans.gate(sym::trait_alias, whole_span);
Ok((ident, ItemKind::TraitAlias(generics, bounds)))
} else {
// It's a normal trait.
generics.where_clause = self.parse_where_clause()?;
let items = self.parse_item_list(attrs, |p| p.parse_trait_item(ForceCollect::No))?;
Ok((
ident,
ItemKind::Trait(Box::new(Trait { is_auto, unsafety, generics, bounds, items })),
))
}
}
pub fn parse_impl_item(
&mut self,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
self.parse_assoc_item(fn_parse_mode, force_collect)
}
pub fn parse_trait_item(
&mut self,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
let fn_parse_mode =
FnParseMode { req_name: |edition| edition >= Edition::Edition2018, req_body: false };
self.parse_assoc_item(fn_parse_mode, force_collect)
}
/// Parses associated items.
fn parse_assoc_item(
&mut self,
fn_parse_mode: FnParseMode,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
|Item { attrs, id, span, vis, ident, kind, tokens }| {
let kind = match AssocItemKind::try_from(kind) {
Ok(kind) => kind,
Err(kind) => match kind {
ItemKind::Static(box StaticItem { ty, mutability: _, expr }) => {
self.dcx().emit_err(errors::AssociatedStaticItemNotAllowed { span });
AssocItemKind::Const(Box::new(ConstItem {
defaultness: Defaultness::Final,
generics: Generics::default(),
ty,
expr,
}))
}
_ => return self.error_bad_item_kind(span, &kind, "`trait`s or `impl`s"),
},
};
Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
},
))
}
/// Parses a `type` alias with the following grammar:
/// ```ebnf
/// TypeAlias = "type" Ident Generics (":" GenericBounds)? WhereClause ("=" Ty)? WhereClause ";" ;
/// ```
/// The `"type"` has already been eaten.
fn parse_type_alias(&mut self, defaultness: Defaultness) -> PResult<'a, ItemInfo> {
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()? } else { Vec::new() };
let before_where_clause = self.parse_where_clause()?;
let ty = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
let after_where_clause = self.parse_where_clause()?;
let where_clauses = TyAliasWhereClauses {
before: TyAliasWhereClause {
has_where_token: before_where_clause.has_where_token,
span: before_where_clause.span,
},
after: TyAliasWhereClause {
has_where_token: after_where_clause.has_where_token,
span: after_where_clause.span,
},
split: before_where_clause.predicates.len(),
};
let mut predicates = before_where_clause.predicates;
predicates.extend(after_where_clause.predicates);
let where_clause = WhereClause {
has_where_token: before_where_clause.has_where_token
|| after_where_clause.has_where_token,
predicates,
span: DUMMY_SP,
};
generics.where_clause = where_clause;
self.expect_semi()?;
Ok((
ident,
ItemKind::TyAlias(Box::new(TyAlias {
defaultness,
generics,
where_clauses,
bounds,
ty,
})),
))
}
/// Parses a `UseTree`.
///
/// ```text
/// 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: ThinVec::new(), span: lo.shrink_to_lo(), tokens: None };
let kind = if self.check(&token::OpenDelim(Delimiter::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::PathSep) {
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::PathSep) {
self.parse_use_tree_glob_or_nested()?
} else {
// Recover from using a colon as path separator.
while self.eat_noexpect(&token::Colon) {
self.dcx()
.emit_err(errors::SingleColonImportPath { span: self.prev_token.span });
// We parse the rest of the path and append it to the original prefix.
self.parse_path_segments(&mut prefix.segments, PathStyle::Mod, None)?;
prefix.span = lo.to(self.prev_token.span);
}
UseTreeKind::Simple(self.parse_rename()?)
}
};
Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.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 {
let lo = self.token.span;
UseTreeKind::Nested {
items: self.parse_use_tree_list()?,
span: lo.to(self.prev_token.span),
}
})
}
/// Parses a `UseTreeKind::Nested(list)`.
///
/// ```text
/// USE_TREE_LIST = ∅ | (USE_TREE `,`)* USE_TREE [`,`]
/// ```
fn parse_use_tree_list(&mut self) -> PResult<'a, ThinVec<(UseTree, ast::NodeId)>> {
self.parse_delim_comma_seq(Delimiter::Brace, |p| {
p.recover_diff_marker();
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, Ident> {
match self.token.ident() {
Some((ident @ Ident { name: kw::Underscore, .. }, IdentIsRaw::No)) => {
self.bump();
Ok(ident)
}
_ => self.parse_ident(),
}
}
/// Parses `extern crate` links.
///
/// # Examples
///
/// ```ignore (illustrative)
/// extern crate foo;
/// extern crate bar as foo;
/// ```
fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
// 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()?;
Ok((item_name, ItemKind::ExternCrate(orig_name)))
}
fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, Ident> {
let ident = if self.token.is_keyword(kw::SelfLower) {
self.parse_path_segment_ident()
} else {
self.parse_ident()
}?;
let dash = token::BinOp(token::BinOpToken::Minus);
if self.token != dash {
return Ok(ident);
}
// Accept `extern crate name-like-this` for better diagnostics.
let mut dashes = vec![];
let mut idents = vec![];
while self.eat(&dash) {
dashes.push(self.prev_token.span);
idents.push(self.parse_ident()?);
}
let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
let mut fixed_name = ident.name.to_string();
for part in idents {
write!(fixed_name, "_{}", part.name).unwrap();
}
self.dcx().emit_err(errors::ExternCrateNameWithDashes {
span: fixed_name_sp,
sugg: errors::ExternCrateNameWithDashesSugg { dashes },
});
Ok(Ident::from_str_and_span(&fixed_name, fixed_name_sp))
}
/// 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,
attrs: &mut AttrVec,
mut unsafety: Unsafe,
) -> PResult<'a, ItemInfo> {
let abi = self.parse_abi(); // ABI?
if unsafety == Unsafe::No
&& self.token.is_keyword(kw::Unsafe)
&& self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Brace))
{
self.expect(&token::OpenDelim(Delimiter::Brace)).unwrap_err().emit();
unsafety = Unsafe::Yes(self.token.span);
self.eat_keyword(kw::Unsafe);
}
let module = ast::ForeignMod {
unsafety,
abi,
items: self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No))?,
};
Ok((Ident::empty(), ItemKind::ForeignMod(module)))
}
/// Parses a foreign item (one in an `extern { ... }` block).
pub fn parse_foreign_item(
&mut self,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: false };
Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
|Item { attrs, id, span, vis, ident, kind, tokens }| {
let kind = match ForeignItemKind::try_from(kind) {
Ok(kind) => kind,
Err(kind) => match kind {
ItemKind::Const(box ConstItem { ty, expr, .. }) => {
let const_span = Some(span.with_hi(ident.span.lo()))
.filter(|span| span.can_be_used_for_suggestions());
self.dcx().emit_err(errors::ExternItemCannotBeConst {
ident_span: ident.span,
const_span,
});
ForeignItemKind::Static(Box::new(StaticForeignItem {
ty,
mutability: Mutability::Not,
expr,
}))
}
_ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
},
};
Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
},
))
}
fn error_bad_item_kind<T>(&self, span: Span, kind: &ItemKind, ctx: &'static str) -> Option<T> {
// FIXME(#100717): needs variant for each `ItemKind` (instead of using `ItemKind::descr()`)
let span = self.psess.source_map().guess_head_span(span);
let descr = kind.descr();
self.dcx().emit_err(errors::BadItemKind { span, descr, ctx });
None
}
fn is_unsafe_foreign_mod(&self) -> bool {
self.token.is_keyword(kw::Unsafe)
&& self.is_keyword_ahead(1, &[kw::Extern])
&& self.look_ahead(
2 + self.look_ahead(2, |t| t.can_begin_literal_maybe_minus() as usize),
|t| t.kind == token::OpenDelim(Delimiter::Brace),
)
}
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;
}
matches!(token.kind, token::BinOp(token::Or) | token::OrOr)
})
} else {
false
}
}
/// Recover on `const mut` with `const` already eaten.
fn recover_const_mut(&mut self, const_span: Span) {
if self.eat_keyword(kw::Mut) {
let span = self.prev_token.span;
self.dcx()
.emit_err(errors::ConstGlobalCannotBeMutable { ident_span: span, const_span });
} else if self.eat_keyword(kw::Let) {
let span = self.prev_token.span;
self.dcx().emit_err(errors::ConstLetMutuallyExclusive { span: const_span.to(span) });
}
}
/// Recover on `const impl` with `const` already eaten.
fn recover_const_impl(
&mut self,
const_span: Span,
attrs: &mut AttrVec,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
let impl_span = self.token.span;
let err = self.expected_ident_found_err();
// Only try to recover if this is implementing a trait for a type
let mut impl_info = match self.parse_item_impl(attrs, defaultness) {
Ok(impl_info) => impl_info,
Err(recovery_error) => {
// Recovery failed, raise the "expected identifier" error
recovery_error.cancel();
return Err(err);
}
};
match &mut impl_info.1 {
ItemKind::Impl(box Impl { of_trait: Some(trai), constness, .. }) => {
*constness = Const::Yes(const_span);
let before_trait = trai.path.span.shrink_to_lo();
let const_up_to_impl = const_span.with_hi(impl_span.lo());
err.with_multipart_suggestion(
"you might have meant to write a const trait impl",
vec![(const_up_to_impl, "".to_owned()), (before_trait, "const ".to_owned())],
Applicability::MaybeIncorrect,
)
.emit();
}
ItemKind::Impl { .. } => return Err(err),
_ => unreachable!(),
}
Ok(impl_info)
}
/// Parse a static item with the prefix `"static" "mut"?` already parsed and stored in `mutability`.
///
/// ```ebnf
/// Static = "static" "mut"? $ident ":" $ty (= $expr)? ";" ;
/// ```
fn parse_static_item(&mut self, mutability: Mutability) -> PResult<'a, (Ident, StaticItem)> {
let ident = self.parse_ident()?;
if self.token.kind == TokenKind::Lt && self.may_recover() {
let generics = self.parse_generics()?;
self.dcx().emit_err(errors::StaticWithGenerics { span: generics.span });
}
// Parse the type of a static item. That is, the `":" $ty` fragment.
// FIXME: This could maybe benefit from `.may_recover()`?
let ty = match (self.eat(&token::Colon), self.check(&token::Eq) | self.check(&token::Semi))
{
(true, false) => self.parse_ty()?,
// If there wasn't a `:` or the colon was followed by a `=` or `;`, recover a missing type.
(colon, _) => self.recover_missing_global_item_type(colon, Some(mutability)),
};
let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
self.expect_semi()?;
Ok((ident, StaticItem { ty, mutability, expr }))
}
/// Parse a constant item with the prefix `"const"` already parsed.
///
/// ```ebnf
/// Const = "const" ($ident | "_") Generics ":" $ty (= $expr)? WhereClause ";" ;
/// ```
fn parse_const_item(&mut self) -> PResult<'a, (Ident, Generics, P<Ty>, Option<P<ast::Expr>>)> {
let ident = self.parse_ident_or_underscore()?;
let mut generics = self.parse_generics()?;
// Check the span for emptiness instead of the list of parameters in order to correctly
// recognize and subsequently flag empty parameter lists (`<>`) as unstable.
if !generics.span.is_empty() {
self.psess.gated_spans.gate(sym::generic_const_items, generics.span);
}
// Parse the type of a constant item. That is, the `":" $ty` fragment.
// FIXME: This could maybe benefit from `.may_recover()`?
let ty = match (
self.eat(&token::Colon),
self.check(&token::Eq) | self.check(&token::Semi) | self.check_keyword(kw::Where),
) {
(true, false) => self.parse_ty()?,
// If there wasn't a `:` or the colon was followed by a `=`, `;` or `where`, recover a missing type.
(colon, _) => self.recover_missing_global_item_type(colon, None),
};
// Proactively parse a where-clause to be able to provide a good error message in case we
// encounter the item body following it.
let before_where_clause =
if self.may_recover() { self.parse_where_clause()? } else { WhereClause::default() };
let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
let after_where_clause = self.parse_where_clause()?;
// Provide a nice error message if the user placed a where-clause before the item body.
// Users may be tempted to write such code if they are still used to the deprecated
// where-clause location on type aliases and associated types. See also #89122.
if before_where_clause.has_where_token
&& let Some(expr) = &expr
{
self.dcx().emit_err(errors::WhereClauseBeforeConstBody {
span: before_where_clause.span,
name: ident.span,
body: expr.span,
sugg: if !after_where_clause.has_where_token {
self.psess.source_map().span_to_snippet(expr.span).ok().map(|body| {
errors::WhereClauseBeforeConstBodySugg {
left: before_where_clause.span.shrink_to_lo(),
snippet: body,
right: before_where_clause.span.shrink_to_hi().to(expr.span),
}
})
} else {
// FIXME(generic_const_items): Provide a structured suggestion to merge the first
// where-clause into the second one.
None
},
});
}
// Merge the predicates of both where-clauses since either one can be relevant.
// If we didn't parse a body (which is valid for associated consts in traits) and we were
// allowed to recover, `before_where_clause` contains the predicates, otherwise they are
// in `after_where_clause`. Further, both of them might contain predicates iff two
// where-clauses were provided which is syntactically ill-formed but we want to recover from
// it and treat them as one large where-clause.
let mut predicates = before_where_clause.predicates;
predicates.extend(after_where_clause.predicates);
let where_clause = WhereClause {
has_where_token: before_where_clause.has_where_token
|| after_where_clause.has_where_token,
predicates,
span: if after_where_clause.has_where_token {
after_where_clause.span
} else {
before_where_clause.span
},
};
if where_clause.has_where_token {
self.psess.gated_spans.gate(sym::generic_const_items, where_clause.span);
}
generics.where_clause = where_clause;
self.expect_semi()?;
Ok((ident, generics, ty, expr))
}
/// We were supposed to parse `":" $ty` but the `:` or the type was missing.
/// This means that the type is missing.
fn recover_missing_global_item_type(
&mut self,
colon_present: bool,
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 colon = match colon_present {
true => "",
false => ":",
};
let span = self.prev_token.span.shrink_to_hi();
let err = self.dcx().create_err(errors::MissingConstType { span, colon, kind });
err.stash(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: ast::DUMMY_NODE_ID, tokens: None })
}
/// Parses an enum declaration.
fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
if self.token.is_keyword(kw::Struct) {
let span = self.prev_token.span.to(self.token.span);
let err = errors::EnumStructMutuallyExclusive { span };
if self.look_ahead(1, |t| t.is_ident()) {
self.bump();
self.dcx().emit_err(err);
} else {
return Err(self.dcx().create_err(err));
}
}
let prev_span = self.prev_token.span;
let id = self.parse_ident()?;
let mut generics = self.parse_generics()?;
generics.where_clause = self.parse_where_clause()?;
// Possibly recover `enum Foo;` instead of `enum Foo {}`
let (variants, _) = if self.token == TokenKind::Semi {
self.dcx().emit_err(errors::UseEmptyBlockNotSemi { span: self.token.span });
self.bump();
(thin_vec![], Trailing::No)
} else {
self.parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant(id.span))
.map_err(|mut err| {
err.span_label(id.span, "while parsing this enum");
if self.token == token::Colon {
let snapshot = self.create_snapshot_for_diagnostic();
self.bump();
match self.parse_ty() {
Ok(_) => {
err.span_suggestion_verbose(
prev_span,
"perhaps you meant to use `struct` here",
"struct",
Applicability::MaybeIncorrect,
);
}
Err(e) => {
e.cancel();
}
}
self.restore_snapshot(snapshot);
}
self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
self.bump(); // }
err
})?
};
let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
Ok((id, ItemKind::Enum(enum_definition, generics)))
}
fn parse_enum_variant(&mut self, span: Span) -> PResult<'a, Option<Variant>> {
self.recover_diff_marker();
let variant_attrs = self.parse_outer_attributes()?;
self.recover_diff_marker();
let help = "enum variants can be `Variant`, `Variant = <integer>`, \
`Variant(Type, ..., TypeN)` or `Variant { fields: Types }`";
self.collect_tokens_trailing_token(
variant_attrs,
ForceCollect::No,
|this, variant_attrs| {
let vlo = this.token.span;
let vis = this.parse_visibility(FollowedByType::No)?;
if !this.recover_nested_adt_item(kw::Enum)? {
return Ok((None, TrailingToken::None));
}
let ident = this.parse_field_ident("enum", vlo)?;
if this.token == token::Not {
if let Err(err) = this.unexpected() {
err.with_note(fluent::parse_macro_expands_to_enum_variant).emit();
}
this.bump();
this.parse_delim_args()?;
return Ok((None, TrailingToken::MaybeComma));
}
let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
// Parse a struct variant.
let (fields, recovered) =
match this.parse_record_struct_body("struct", ident.span, false) {
Ok((fields, recovered)) => (fields, recovered),
Err(mut err) => {
if this.token == token::Colon {
// We handle `enum` to `struct` suggestion in the caller.
return Err(err);
}
this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
this.bump(); // }
err.span_label(span, "while parsing this enum");
err.help(help);
let guar = err.emit();
(thin_vec![], Recovered::Yes(guar))
}
};
VariantData::Struct { fields, recovered: recovered.into() }
} else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
let body = match this.parse_tuple_struct_body() {
Ok(body) => body,
Err(mut err) => {
if this.token == token::Colon {
// We handle `enum` to `struct` suggestion in the caller.
return Err(err);
}
this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis)]);
this.bump(); // )
err.span_label(span, "while parsing this enum");
err.help(help);
err.emit();
thin_vec![]
}
};
VariantData::Tuple(body, DUMMY_NODE_ID)
} else {
VariantData::Unit(DUMMY_NODE_ID)
};
let disr_expr =
if this.eat(&token::Eq) { Some(this.parse_expr_anon_const()?) } else { None };
let vr = ast::Variant {
ident,
vis,
id: DUMMY_NODE_ID,
attrs: variant_attrs,
data: struct_def,
disr_expr,
span: vlo.to(this.prev_token.span),
is_placeholder: false,
};
Ok((Some(vr), TrailingToken::MaybeComma))
},
)
.map_err(|mut err| {
err.help(help);
err
})
}
/// 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) {
let tuple_struct_body;
(generics.where_clause, tuple_struct_body) =
self.parse_struct_where_clause(class_name, generics.span)?;
if let Some(body) = tuple_struct_body {
// If we see a misplaced tuple struct body: `struct Foo<T> where T: Copy, (T);`
let body = VariantData::Tuple(body, DUMMY_NODE_ID);
self.expect_semi()?;
body
} else 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(
"struct",
class_name.span,
generics.where_clause.has_where_token,
)?;
VariantData::Struct { fields, recovered: recovered.into() }
}
// 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(Delimiter::Brace) {
let (fields, recovered) = self.parse_record_struct_body(
"struct",
class_name.span,
generics.where_clause.has_where_token,
)?;
VariantData::Struct { fields, recovered: recovered.into() }
// Tuple-style struct definition with optional where-clause.
} else if self.token == token::OpenDelim(Delimiter::Parenthesis) {
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 err =
errors::UnexpectedTokenAfterStructName::new(self.token.span, self.token.clone());
return Err(self.dcx().create_err(err));
};
Ok((class_name, ItemKind::Struct(vdata, generics)))
}
/// 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(
"union",
class_name.span,
generics.where_clause.has_where_token,
)?;
VariantData::Struct { fields, recovered: recovered.into() }
} else if self.token == token::OpenDelim(Delimiter::Brace) {
let (fields, recovered) = self.parse_record_struct_body(
"union",
class_name.span,
generics.where_clause.has_where_token,
)?;
VariantData::Struct { fields, recovered: recovered.into() }
} 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.dcx().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)))
}
pub(crate) fn parse_record_struct_body(
&mut self,
adt_ty: &str,
ident_span: Span,
parsed_where: bool,
) -> PResult<'a, (ThinVec<FieldDef>, Recovered)> {
let mut fields = ThinVec::new();
let mut recovered = Recovered::No;
if self.eat(&token::OpenDelim(Delimiter::Brace)) {
while self.token != token::CloseDelim(Delimiter::Brace) {
match self.parse_field_def(adt_ty) {
Ok(field) => {
fields.push(field);
}
Err(mut err) => {
self.consume_block(Delimiter::Brace, ConsumeClosingDelim::No);
err.span_label(ident_span, format!("while parsing this {adt_ty}"));
let guar = err.emit();
recovered = Recovered::Yes(guar);
break;
}
}
}
self.eat(&token::CloseDelim(Delimiter::Brace));
} else {
let token_str = super::token_descr(&self.token);
let msg = format!(
"expected {}`{{` after struct name, found {}",
if parsed_where { "" } else { "`where`, or " },
token_str
);
let mut err = self.dcx().struct_span_err(self.token.span, msg);
err.span_label(
self.token.span,
format!(
"expected {}`{{` after struct name",
if parsed_where { "" } else { "`where`, or " }
),
);
return Err(err);
}
Ok((fields, recovered))
}
pub(super) fn parse_tuple_struct_body(&mut self) -> PResult<'a, ThinVec<FieldDef>> {
// 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()?;
p.collect_tokens_trailing_token(attrs, ForceCollect::No, |p, attrs| {
let mut snapshot = None;
if p.is_diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) {
// Account for `<<<<<<<` diff markers. We can't proactively error here because
// that can be a valid type start, so we snapshot and reparse only we've
// encountered another parse error.
snapshot = Some(p.create_snapshot_for_diagnostic());
}
let lo = p.token.span;
let vis = match p.parse_visibility(FollowedByType::Yes) {
Ok(vis) => vis,
Err(err) => {
if let Some(ref mut snapshot) = snapshot {
snapshot.recover_diff_marker();
}
return Err(err);
}
};
let ty = match p.parse_ty() {
Ok(ty) => ty,
Err(err) => {
if let Some(ref mut snapshot) = snapshot {
snapshot.recover_diff_marker();
}
return Err(err);
}
};
Ok((
FieldDef {
span: lo.to(ty.span),
vis,
ident: None,
id: DUMMY_NODE_ID,
ty,
attrs,
is_placeholder: false,
},
TrailingToken::MaybeComma,
))
})
})
.map(|(r, _)| r)
}
/// Parses an element of a struct declaration.
fn parse_field_def(&mut self, adt_ty: &str) -> PResult<'a, FieldDef> {
self.recover_diff_marker();
let attrs = self.parse_outer_attributes()?;
self.recover_diff_marker();
self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
let lo = this.token.span;
let vis = this.parse_visibility(FollowedByType::No)?;
this.parse_single_struct_field(adt_ty, lo, vis, attrs)
.map(|field| (field, TrailingToken::None))
})
}
/// Parses a structure field declaration.
fn parse_single_struct_field(
&mut self,
adt_ty: &str,
lo: Span,
vis: Visibility,
attrs: AttrVec,
) -> PResult<'a, FieldDef> {
let mut seen_comma: bool = false;
let a_var = self.parse_name_and_ty(adt_ty, lo, vis, attrs)?;
if self.token == token::Comma {
seen_comma = true;
}
if self.eat(&token::Semi) {
let sp = self.prev_token.span;
let mut err =
self.dcx().struct_span_err(sp, format!("{adt_ty} fields are separated by `,`"));
err.span_suggestion_short(
sp,
"replace `;` with `,`",
",",
Applicability::MachineApplicable,
);
return Err(err);
}
match self.token.kind {
token::Comma => {
self.bump();
}
token::CloseDelim(Delimiter::Brace) => {}
token::DocComment(..) => {
let previous_span = self.prev_token.span;
let mut err = errors::DocCommentDoesNotDocumentAnything {
span: self.token.span,
missing_comma: None,
};
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 && comma_after_doc_seen {
seen_comma = true;
}
if comma_after_doc_seen || self.token == token::CloseDelim(Delimiter::Brace) {
self.dcx().emit_err(err);
} else {
if !seen_comma {
let sp = previous_span.shrink_to_hi();
err.missing_comma = Some(sp);
}
return Err(self.dcx().create_err(err));
}
}
_ => {
let sp = self.prev_token.span.shrink_to_hi();
let msg =
format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token));
// Try to recover extra trailing angle brackets
if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
if let Some(last_segment) = segments.last() {
let guar = self.check_trailing_angle_brackets(
last_segment,
&[&token::Comma, &token::CloseDelim(Delimiter::Brace)],
);
if let Some(_guar) = guar {
// Handle a case like `Vec<u8>>,` where we can continue parsing fields
// after the comma
self.eat(&token::Comma);
// `check_trailing_angle_brackets` already emitted a nicer error, as
// proven by the presence of `_guar`. We can continue parsing.
return Ok(a_var);
}
}
}
let mut err = self.dcx().struct_span_err(sp, msg);
if self.token.is_ident()
|| (self.token.kind == TokenKind::Pound
&& (self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Bracket))))
{
// This is likely another field, TokenKind::Pound is used for `#[..]`
// attribute for next field. Emit the diagnostic and continue parsing.
err.span_suggestion(
sp,
"try adding a comma",
",",
Applicability::MachineApplicable,
);
err.emit();
} else {
return Err(err);
}
}
}
Ok(a_var)
}
fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
if let Err(err) = self.expect(&token::Colon) {
let sm = self.psess.source_map();
let eq_typo = self.token.kind == token::Eq && self.look_ahead(1, |t| t.is_path_start());
let semi_typo = self.token.kind == token::Semi
&& self.look_ahead(1, |t| {
t.is_path_start()
// We check that we are in a situation like `foo; bar` to avoid bad suggestions
// when there's no type and `;` was used instead of a comma.
&& match (sm.lookup_line(self.token.span.hi()), sm.lookup_line(t.span.lo())) {
(Ok(l), Ok(r)) => l.line == r.line,
_ => true,
}
});
if eq_typo || semi_typo {
self.bump();
// Gracefully handle small typos.
err.with_span_suggestion_short(
self.prev_token.span,
"field names and their types are separated with `:`",
":",
Applicability::MachineApplicable,
)
.emit();
} else {
return Err(err);
}
}
Ok(())
}
/// Parses a structure field.
fn parse_name_and_ty(
&mut self,
adt_ty: &str,
lo: Span,
vis: Visibility,
attrs: AttrVec,
) -> PResult<'a, FieldDef> {
let name = self.parse_field_ident(adt_ty, lo)?;
if self.token.kind == token::Not {
if let Err(mut err) = self.unexpected() {
// Encounter the macro invocation
err.subdiagnostic(self.dcx(), MacroExpandsToAdtField { adt_ty });
return Err(err);
}
}
self.expect_field_ty_separator()?;
let ty = self.parse_ty_for_field_def()?;
if self.token.kind == token::Colon && self.look_ahead(1, |tok| tok.kind != token::Colon) {
self.dcx().emit_err(errors::SingleColonStructType { span: self.token.span });
}
if self.token.kind == token::Eq {
self.bump();
let const_expr = self.parse_expr_anon_const()?;
let sp = ty.span.shrink_to_hi().to(const_expr.value.span);
self.dcx().emit_err(errors::EqualsStructDefault { span: sp });
}
Ok(FieldDef {
span: lo.to(self.prev_token.span),
ident: Some(name),
vis,
id: DUMMY_NODE_ID,
ty,
attrs,
is_placeholder: false,
})
}
/// Parses a field identifier. Specialized version of `parse_ident_common`
/// for better diagnostics and suggestions.
fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
let (ident, is_raw) = self.ident_or_err(true)?;
if ident.name == kw::Underscore {
self.psess.gated_spans.gate(sym::unnamed_fields, lo);
} else if matches!(is_raw, IdentIsRaw::No) && ident.is_reserved() {
let snapshot = self.create_snapshot_for_diagnostic();
let err = if self.check_fn_front_matter(false, Case::Sensitive) {
let inherited_vis =
Visibility { span: DUMMY_SP, kind: VisibilityKind::Inherited, tokens: None };
// We use `parse_fn` to get a span for the function
let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
match self.parse_fn(
&mut AttrVec::new(),
fn_parse_mode,
lo,
&inherited_vis,
Case::Insensitive,
) {
Ok(_) => {
self.dcx().struct_span_err(
lo.to(self.prev_token.span),
format!("functions are not allowed in {adt_ty} definitions"),
)
.with_help(
"unlike in C++, Java, and C#, functions are declared in `impl` blocks",
)
.with_help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information")
}
Err(err) => {
err.cancel();
self.restore_snapshot(snapshot);
self.expected_ident_found_err()
}
}
} else if self.eat_keyword(kw::Struct) {
match self.parse_item_struct() {
Ok((ident, _)) => self
.dcx()
.struct_span_err(
lo.with_hi(ident.span.hi()),
format!("structs are not allowed in {adt_ty} definitions"),
)
.with_help(
"consider creating a new `struct` definition instead of nesting",
),
Err(err) => {
err.cancel();
self.restore_snapshot(snapshot);
self.expected_ident_found_err()
}
}
} else {
let mut err = self.expected_ident_found_err();
if self.eat_keyword_noexpect(kw::Let)
&& let removal_span = self.prev_token.span.until(self.token.span)
&& let Ok(ident) = self
.parse_ident_common(false)
// Cancel this error, we don't need it.
.map_err(|err| err.cancel())
&& self.token.kind == TokenKind::Colon
{
err.span_suggestion(
removal_span,
"remove this `let` keyword",
String::new(),
Applicability::MachineApplicable,
);
err.note("the `let` keyword is not allowed in `struct` fields");
err.note("see <https://doc.rust-lang.org/book/ch05-01-defining-structs.html> for more information");
err.emit();
return Ok(ident);
} else {
self.restore_snapshot(snapshot);
}
err
};
return Err(err);
}
self.bump();
Ok(ident)
}
/// Parses a declarative macro 2.0 definition.
/// The `macro` keyword has already been parsed.
/// ```ebnf
/// MacBody = "{" TOKEN_STREAM "}" ;
/// MacParams = "(" TOKEN_STREAM ")" ;
/// DeclMac = "macro" Ident MacParams? MacBody ;
/// ```
fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
let ident = self.parse_ident()?;
let body = if self.check(&token::OpenDelim(Delimiter::Brace)) {
self.parse_delim_args()? // `MacBody`
} else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
let params = self.parse_token_tree(); // `MacParams`
let pspan = params.span();
if !self.check(&token::OpenDelim(Delimiter::Brace)) {
self.unexpected()?;
}
let body = self.parse_token_tree(); // `MacBody`
// Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
let bspan = body.span();
let arrow = TokenTree::token_alone(token::FatArrow, pspan.between(bspan)); // `=>`
let tokens = TokenStream::new(vec![params, arrow, body]);
let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
P(DelimArgs { dspan, delim: Delimiter::Brace, tokens })
} else {
self.unexpected_any()?
};
self.psess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: false })))
}
/// Is this a possibly malformed start of a `macro_rules! foo` item definition?
fn is_macro_rules_item(&mut self) -> IsMacroRulesItem {
if self.check_keyword(kw::MacroRules) {
let macro_rules_span = self.token.span;
if self.look_ahead(1, |t| *t == token::Not) && self.look_ahead(2, |t| t.is_ident()) {
return IsMacroRulesItem::Yes { has_bang: true };
} else if self.look_ahead(1, |t| (t.is_ident())) {
// macro_rules foo
self.dcx().emit_err(errors::MacroRulesMissingBang {
span: macro_rules_span,
hi: macro_rules_span.shrink_to_hi(),
});
return IsMacroRulesItem::Yes { has_bang: false };
}
}
IsMacroRulesItem::No
}
/// Parses a `macro_rules! foo { ... }` declarative macro.
fn parse_item_macro_rules(
&mut self,
vis: &Visibility,
has_bang: bool,
) -> PResult<'a, ItemInfo> {
self.expect_keyword(kw::MacroRules)?; // `macro_rules`
if has_bang {
self.expect(&token::Not)?; // `!`
}
let ident = self.parse_ident()?;
if self.eat(&token::Not) {
// Handle macro_rules! foo!
let span = self.prev_token.span;
self.dcx().emit_err(errors::MacroNameRemoveBang { span });
}
let body = self.parse_delim_args()?;
self.eat_semi_for_macro_if_needed(&body);
self.complain_if_pub_macro(vis, true);
Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: true })))
}
/// Item macro invocations or `macro_rules!` definitions need inherited visibility.
/// If that's not the case, emit an error.
fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
if let VisibilityKind::Inherited = vis.kind {
return;
}
let vstr = pprust::vis_to_string(vis);
let vstr = vstr.trim_end();
if macro_rules {
self.dcx().emit_err(errors::MacroRulesVisibility { span: vis.span, vis: vstr });
} else {
self.dcx().emit_err(errors::MacroInvocationVisibility { span: vis.span, vis: vstr });
}
}
fn eat_semi_for_macro_if_needed(&mut self, args: &DelimArgs) {
if args.need_semicolon() && !self.eat(&token::Semi) {
self.report_invalid_macro_expansion_item(args);
}
}
fn report_invalid_macro_expansion_item(&self, args: &DelimArgs) {
let span = args.dspan.entire();
let mut err = self.dcx().struct_span_err(
span,
"macros that expand to items must be delimited with braces or followed by a semicolon",
);
// FIXME: This will make us not emit the help even for declarative
// macros within the same crate (that we can fix), which is sad.
if !span.from_expansion() {
let DelimSpan { open, close } = args.dspan;
err.multipart_suggestion(
"change the delimiters to curly braces",
vec![(open, "{".to_string()), (close, '}'.to_string())],
Applicability::MaybeIncorrect,
);
err.span_suggestion(
span.with_neighbor(self.token.span).shrink_to_hi(),
"add a semicolon",
';',
Applicability::MaybeIncorrect,
);
}
err.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(ForceCollect::No)?;
self.dcx().emit_err(errors::NestedAdt {
span: kw_token.span,
item: item.unwrap().span,
kw_str,
keyword: keyword.as_str(),
});
// We successfully parsed the item but we must inform the caller about nested problem.
return Ok(false);
}
Ok(true)
}
}
/// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
///
/// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
///
/// This function pointer accepts an edition, because in edition 2015, trait declarations
/// were allowed to omit parameter names. In 2018, they became required.
type ReqName = fn(Edition) -> bool;
/// Parsing configuration for functions.
///
/// The syntax of function items is slightly different within trait definitions,
/// impl blocks, and modules. It is still parsed using the same code, just with
/// different flags set, so that even when the input is wrong and produces a parse
/// error, it still gets into the AST and the rest of the parser and
/// type checker can run.
#[derive(Clone, Copy)]
pub(crate) struct FnParseMode {
/// A function pointer that decides if, per-parameter `p`, `p` must have a
/// pattern or just a type. This field affects parsing of the parameters list.
///
/// ```text
/// fn foo(alef: A) -> X { X::new() }
/// -----^^ affects parsing this part of the function signature
/// |
/// if req_name returns false, then this name is optional
///
/// fn bar(A) -> X;
/// ^
/// |
/// if req_name returns true, this is an error
/// ```
///
/// Calling this function pointer should only return false if:
///
/// * The item is being parsed inside of a trait definition.
/// Within an impl block or a module, it should always evaluate
/// to true.
/// * The span is from Edition 2015. In particular, you can get a
/// 2015 span inside a 2021 crate using macros.
pub req_name: ReqName,
/// If this flag is set to `true`, then plain, semicolon-terminated function
/// prototypes are not allowed here.
///
/// ```text
/// fn foo(alef: A) -> X { X::new() }
/// ^^^^^^^^^^^^
/// |
/// this is always allowed
///
/// fn bar(alef: A, bet: B) -> X;
/// ^
/// |
/// if req_body is set to true, this is an error
/// ```
///
/// This field should only be set to false if the item is inside of a trait
/// definition or extern block. Within an impl block or a module, it should
/// always be set to true.
pub req_body: bool,
}
/// Parsing of functions and methods.
impl<'a> Parser<'a> {
/// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
fn parse_fn(
&mut self,
attrs: &mut AttrVec,
fn_parse_mode: FnParseMode,
sig_lo: Span,
vis: &Visibility,
case: Case,
) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
let fn_span = self.token.span;
let header = self.parse_fn_front_matter(vis, case)?; // `const ... fn`
let ident = self.parse_ident()?; // `foo`
let mut generics = self.parse_generics()?; // `<'a, T, ...>`
let decl = match self.parse_fn_decl(
fn_parse_mode.req_name,
AllowPlus::Yes,
RecoverReturnSign::Yes,
) {
Ok(decl) => decl,
Err(old_err) => {
// If we see `for Ty ...` then user probably meant `impl` item.
if self.token.is_keyword(kw::For) {
old_err.cancel();
return Err(self.dcx().create_err(errors::FnTypoWithImpl { fn_span }));
} else {
return Err(old_err);
}
}
};
generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
let mut sig_hi = self.prev_token.span;
let body = self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body)?; // `;` or `{ ... }`.
let fn_sig_span = sig_lo.to(sig_hi);
Ok((ident, FnSig { header, decl, span: fn_sig_span }, generics, body))
}
/// Parse the "body" of a function.
/// This can either be `;` when there's no body,
/// or e.g. a block when the function is a provided one.
fn parse_fn_body(
&mut self,
attrs: &mut AttrVec,
ident: &Ident,
sig_hi: &mut Span,
req_body: bool,
) -> PResult<'a, Option<P<Block>>> {
let has_semi = if req_body {
self.token.kind == TokenKind::Semi
} else {
// Only include `;` in list of expected tokens if body is not required
self.check(&TokenKind::Semi)
};
let (inner_attrs, body) = if has_semi {
// Include the trailing semicolon in the span of the signature
self.expect_semi()?;
*sig_hi = self.prev_token.span;
(AttrVec::new(), None)
} else if self.check(&token::OpenDelim(Delimiter::Brace)) || self.token.is_whole_block() {
self.parse_block_common(self.token.span, BlockCheckMode::Default, false)
.map(|(attrs, body)| (attrs, Some(body)))?
} else if self.token.kind == token::Eq {
// Recover `fn foo() = $expr;`.
self.bump(); // `=`
let eq_sp = self.prev_token.span;
let _ = self.parse_expr()?;
self.expect_semi()?; // `;`
let span = eq_sp.to(self.prev_token.span);
let guar = self.dcx().emit_err(errors::FunctionBodyEqualsExpr {
span,
sugg: errors::FunctionBodyEqualsExprSugg { eq: eq_sp, semi: self.prev_token.span },
});
(AttrVec::new(), Some(self.mk_block_err(span, guar)))
} else {
let expected = if req_body {
&[token::OpenDelim(Delimiter::Brace)][..]
} else {
&[token::Semi, token::OpenDelim(Delimiter::Brace)]
};
if let Err(mut err) = self.expected_one_of_not_found(&[], expected) {
if self.token.kind == token::CloseDelim(Delimiter::Brace) {
// The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
// the AST for typechecking.
err.span_label(ident.span, "while parsing this `fn`");
err.emit();
} else {
// check for typo'd Fn* trait bounds such as
// fn foo<F>() where F: FnOnce -> () {}
if self.token.kind == token::RArrow {
let machine_applicable = [sym::FnOnce, sym::FnMut, sym::Fn]
.into_iter()
.any(|s| self.prev_token.is_ident_named(s));
err.subdiagnostic(
self.dcx(),
errors::FnTraitMissingParen {
span: self.prev_token.span,
machine_applicable,
},
);
}
return Err(err);
}
}
(AttrVec::new(), None)
};
attrs.extend(inner_attrs);
Ok(body)
}
/// Is the current token the start of an `FnHeader` / not a valid parse?
///
/// `check_pub` adds additional `pub` to the checks in case users place it
/// wrongly, can be used to ensure `pub` never comes after `default`.
pub(super) fn check_fn_front_matter(&mut self, check_pub: bool, case: Case) -> bool {
// We use an over-approximation here.
// `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
// `pub` is added in case users got confused with the ordering like `async pub fn`,
// only if it wasn't preceded by `default` as `default pub` is invalid.
let quals: &[Symbol] = if check_pub {
&[kw::Pub, kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
} else {
&[kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
};
self.check_keyword_case(kw::Fn, case) // Definitely an `fn`.
// `$qual fn` or `$qual $qual`:
|| quals.iter().any(|&kw| self.check_keyword_case(kw, case))
&& self.look_ahead(1, |t| {
// `$qual fn`, e.g. `const fn` or `async fn`.
t.is_keyword_case(kw::Fn, case)
// Two qualifiers `$qual $qual` is enough, e.g. `async unsafe`.
|| (
(
t.is_non_raw_ident_where(|i|
quals.contains(&i.name)
// Rule out 2015 `const async: T = val`.
&& i.is_reserved()
)
|| case == Case::Insensitive
&& t.is_non_raw_ident_where(|i| quals.iter().any(|qual| qual.as_str() == i.name.as_str().to_lowercase()))
)
// Rule out `unsafe extern {`.
&& !self.is_unsafe_foreign_mod()
// Rule out `async gen {` and `async gen move {`
&& !self.is_async_gen_block())
})
// `extern ABI fn`
|| self.check_keyword_case(kw::Extern, case)
&& self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
&& (self.look_ahead(2, |t| t.is_keyword_case(kw::Fn, case)) ||
// this branch is only for better diagnostic in later, `pub` is not allowed here
(self.may_recover()
&& self.look_ahead(2, |t| t.is_keyword(kw::Pub))
&& self.look_ahead(3, |t| t.is_keyword_case(kw::Fn, case))))
}
/// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
/// up to and including the `fn` keyword. The formal grammar is:
///
/// ```text
/// Extern = "extern" StringLit? ;
/// FnQual = "const"? "async"? "unsafe"? Extern? ;
/// FnFrontMatter = FnQual "fn" ;
/// ```
///
/// `vis` represents the visibility that was already parsed, if any. Use
/// `Visibility::Inherited` when no visibility is known.
pub(super) fn parse_fn_front_matter(
&mut self,
orig_vis: &Visibility,
case: Case,
) -> PResult<'a, FnHeader> {
let sp_start = self.token.span;
let constness = self.parse_constness(case);
let async_start_sp = self.token.span;
let coroutine_kind = self.parse_coroutine_kind(case);
let unsafe_start_sp = self.token.span;
let unsafety = self.parse_unsafety(case);
let ext_start_sp = self.token.span;
let ext = self.parse_extern(case);
if let Some(CoroutineKind::Async { span, .. }) = coroutine_kind {
if span.is_rust_2015() {
self.dcx().emit_err(errors::AsyncFnIn2015 {
span,
help: errors::HelpUseLatestEdition::new(),
});
}
}
match coroutine_kind {
Some(CoroutineKind::Gen { span, .. }) | Some(CoroutineKind::AsyncGen { span, .. }) => {
self.psess.gated_spans.gate(sym::gen_blocks, span);
}
Some(CoroutineKind::Async { .. }) | None => {}
}
if !self.eat_keyword_case(kw::Fn, case) {
// 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.
match self.expect_one_of(&[], &[]) {
Ok(Recovered::Yes(_)) => {}
Ok(Recovered::No) => unreachable!(),
Err(mut err) => {
// Qualifier keywords ordering check
enum WrongKw {
Duplicated(Span),
Misplaced(Span),
}
// We may be able to recover
let mut recover_constness = constness;
let mut recover_coroutine_kind = coroutine_kind;
let mut recover_unsafety = unsafety;
// This will allow the machine fix to directly place the keyword in the correct place or to indicate
// that the keyword is already present and the second instance should be removed.
let wrong_kw = if self.check_keyword(kw::Const) {
match constness {
Const::Yes(sp) => Some(WrongKw::Duplicated(sp)),
Const::No => {
recover_constness = Const::Yes(self.token.span);
Some(WrongKw::Misplaced(async_start_sp))
}
}
} else if self.check_keyword(kw::Async) {
match coroutine_kind {
Some(CoroutineKind::Async { span, .. }) => {
Some(WrongKw::Duplicated(span))
}
Some(CoroutineKind::AsyncGen { span, .. }) => {
Some(WrongKw::Duplicated(span))
}
Some(CoroutineKind::Gen { .. }) => {
recover_coroutine_kind = Some(CoroutineKind::AsyncGen {
span: self.token.span,
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
});
// FIXME(gen_blocks): This span is wrong, didn't want to think about it.
Some(WrongKw::Misplaced(unsafe_start_sp))
}
None => {
recover_coroutine_kind = Some(CoroutineKind::Async {
span: self.token.span,
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
});
Some(WrongKw::Misplaced(unsafe_start_sp))
}
}
} else if self.check_keyword(kw::Unsafe) {
match unsafety {
Unsafe::Yes(sp) => Some(WrongKw::Duplicated(sp)),
Unsafe::No => {
recover_unsafety = Unsafe::Yes(self.token.span);
Some(WrongKw::Misplaced(ext_start_sp))
}
}
} else {
None
};
// The keyword is already present, suggest removal of the second instance
if let Some(WrongKw::Duplicated(original_sp)) = wrong_kw {
let original_kw = self
.span_to_snippet(original_sp)
.expect("Span extracted directly from keyword should always work");
err.span_suggestion(
self.token.uninterpolated_span(),
format!("`{original_kw}` already used earlier, remove this one"),
"",
Applicability::MachineApplicable,
)
.span_note(original_sp, format!("`{original_kw}` first seen here"));
}
// The keyword has not been seen yet, suggest correct placement in the function front matter
else if let Some(WrongKw::Misplaced(correct_pos_sp)) = wrong_kw {
let correct_pos_sp = correct_pos_sp.to(self.prev_token.span);
if let Ok(current_qual) = self.span_to_snippet(correct_pos_sp) {
let misplaced_qual_sp = self.token.uninterpolated_span();
let misplaced_qual = self.span_to_snippet(misplaced_qual_sp).unwrap();
err.span_suggestion(
correct_pos_sp.to(misplaced_qual_sp),
format!("`{misplaced_qual}` must come before `{current_qual}`"),
format!("{misplaced_qual} {current_qual}"),
Applicability::MachineApplicable,
).note("keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`");
}
}
// Recover incorrect visibility order such as `async pub`
else if self.check_keyword(kw::Pub) {
let sp = sp_start.to(self.prev_token.span);
if let Ok(snippet) = self.span_to_snippet(sp) {
let current_vis = match self.parse_visibility(FollowedByType::No) {
Ok(v) => v,
Err(d) => {
d.cancel();
return Err(err);
}
};
let vs = pprust::vis_to_string(&current_vis);
let vs = vs.trim_end();
// There was no explicit visibility
if matches!(orig_vis.kind, VisibilityKind::Inherited) {
err.span_suggestion(
sp_start.to(self.prev_token.span),
format!("visibility `{vs}` must come before `{snippet}`"),
format!("{vs} {snippet}"),
Applicability::MachineApplicable,
);
}
// There was an explicit visibility
else {
err.span_suggestion(
current_vis.span,
"there is already a visibility modifier, remove one",
"",
Applicability::MachineApplicable,
)
.span_note(orig_vis.span, "explicit visibility first seen here");
}
}
}
// FIXME(gen_blocks): add keyword recovery logic for genness
if wrong_kw.is_some()
&& self.may_recover()
&& self.look_ahead(1, |tok| tok.is_keyword_case(kw::Fn, case))
{
// Advance past the misplaced keyword and `fn`
self.bump();
self.bump();
err.emit();
return Ok(FnHeader {
constness: recover_constness,
unsafety: recover_unsafety,
coroutine_kind: recover_coroutine_kind,
ext,
});
}
return Err(err);
}
}
}
Ok(FnHeader { constness, unsafety, coroutine_kind, ext })
}
/// Parses the parameter list and result type of a function declaration.
pub(super) fn parse_fn_decl(
&mut self,
req_name: ReqName,
ret_allow_plus: AllowPlus,
recover_return_sign: RecoverReturnSign,
) -> PResult<'a, P<FnDecl>> {
Ok(P(FnDecl {
inputs: self.parse_fn_params(req_name)?,
output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes, recover_return_sign)?,
}))
}
/// Parses the parameter list of a function, including the `(` and `)` delimiters.
pub(super) fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, ThinVec<Param>> {
let mut first_param = true;
// Parse the arguments, starting out with `self` being allowed...
if self.token.kind != TokenKind::OpenDelim(Delimiter::Parenthesis)
// might be typo'd trait impl, handled elsewhere
&& !self.token.is_keyword(kw::For)
{
// recover from missing argument list, e.g. `fn main -> () {}`
self.dcx()
.emit_err(errors::MissingFnParams { span: self.prev_token.span.shrink_to_hi() });
return Ok(ThinVec::new());
}
let (mut params, _) = self.parse_paren_comma_seq(|p| {
p.recover_diff_marker();
let snapshot = p.create_snapshot_for_diagnostic();
let param = p.parse_param_general(req_name, first_param).or_else(|e| {
let guar = e.emit();
let lo = p.prev_token.span;
p.restore_snapshot(snapshot);
// Skip every token until next possible arg or end.
p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(Delimiter::Parenthesis)]);
// Create a placeholder argument for proper arg count (issue #34264).
Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span)), guar))
});
// ...now that we've parsed the first argument, `self` is no longer allowed.
first_param = false;
param
})?;
// Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
self.deduplicate_recovered_params_names(&mut params);
Ok(params)
}
/// Parses a single function parameter.
///
/// - `self` is syntactically allowed when `first_param` holds.
fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
let lo = self.token.span;
let attrs = self.parse_outer_attributes()?;
self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
// Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
if let Some(mut param) = this.parse_self_param()? {
param.attrs = attrs;
let res = if first_param { Ok(param) } else { this.recover_bad_self_param(param) };
return Ok((res?, TrailingToken::None));
}
let is_name_required = match this.token.kind {
token::DotDotDot => false,
_ => req_name(this.token.span.with_neighbor(this.prev_token.span).edition()),
};
let (pat, ty) = if is_name_required || this.is_named_param() {
debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
let (pat, colon) = this.parse_fn_param_pat_colon()?;
if !colon {
let mut err = this.unexpected().unwrap_err();
return if let Some(ident) =
this.parameter_without_type(&mut err, pat, is_name_required, first_param)
{
let guar = err.emit();
Ok((dummy_arg(ident, guar), TrailingToken::None))
} else {
Err(err)
};
}
this.eat_incorrect_doc_comment_for_param_type();
(pat, this.parse_ty_for_param()?)
} else {
debug!("parse_param_general ident_to_pat");
let parser_snapshot_before_ty = this.create_snapshot_for_diagnostic();
this.eat_incorrect_doc_comment_for_param_type();
let mut ty = this.parse_ty_for_param();
if ty.is_ok()
&& this.token != token::Comma
&& this.token != token::CloseDelim(Delimiter::Parenthesis)
{
// 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 = this.unexpected_any();
}
match ty {
Ok(ty) => {
let ident = Ident::new(kw::Empty, this.prev_token.span);
let bm = BindingMode::NONE;
let pat = this.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 this.token == token::DotDotDot => return Err(err),
// Recover from attempting to parse the argument as a type without pattern.
Err(err) => {
err.cancel();
this.restore_snapshot(parser_snapshot_before_ty);
this.recover_arg_parse()?
}
}
};
let span = lo.to(this.prev_token.span);
Ok((
Param { attrs, id: ast::DUMMY_NODE_ID, is_placeholder: false, pat, span, ty },
TrailingToken::None,
))
})
}
/// Returns the parsed optional self parameter and whether a self shortcut was used.
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.ident() {
Some((ident, IdentIsRaw::No)) => {
this.bump();
ident
}
_ => 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::PathSep)
};
// 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_token.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| {
this.dcx().emit_err(errors::SelfArgumentPointer { span: this.token.span });
Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_token.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.uninterpolate().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_token.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(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(kw::Mut) => 1,
_ => 0,
};
self.look_ahead(offset, |t| t.is_ident())
&& self.look_ahead(offset + 1, |t| t == &token::Colon)
}
fn recover_self_param(&mut self) -> bool {
matches!(
self.parse_outer_attributes()
.and_then(|_| self.parse_self_param())
.map_err(|e| e.cancel()),
Ok(Some(_))
)
}
}
enum IsMacroRulesItem {
Yes { has_bang: bool },
No,
}