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android / toolchain / rustc / 32f7835b4f844d645621e83c89a3178ef87b0d69 / . / compiler / rustc_parse / src / parser / item.rs
blob: acf3867cf8920608c2ad4b40858c0de037656210 [file] [log] [blame]
use super::diagnostics::{dummy_arg, ConsumeClosingDelim, Error};
use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
use super::{AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, TrailingToken};
use rustc_ast::ast::*;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
use rustc_ast::{self as ast, AttrVec, Attribute, DUMMY_NODE_ID};
use rustc_ast::{Async, Const, Defaultness, IsAuto, Mutability, Unsafe, UseTree, UseTreeKind};
use rustc_ast::{BindingMode, Block, FnDecl, FnSig, Param, SelfKind};
use rustc_ast::{EnumDef, FieldDef, Generics, TraitRef, Ty, TyKind, Variant, VariantData};
use rustc_ast::{FnHeader, ForeignItem, Path, PathSegment, Visibility, VisibilityKind};
use rustc_ast::{MacArgs, MacCall, MacDelimiter};
use rustc_ast_pretty::pprust;
use rustc_errors::{struct_span_err, Applicability, PResult, StashKey};
use rustc_span::edition::{Edition, LATEST_STABLE_EDITION};
use rustc_span::source_map::{self, Span};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use std::convert::TryFrom;
use std::mem;
use tracing::debug;
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, span) = self.parse_mod(&token::Eof)?;
let proc_macros = Vec::new(); // Filled in by `proc_macro_harness::inject()`.
Ok(ast::Crate { attrs, items, span, proc_macros })
}
/// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
fn parse_item_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety();
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(token::Brace))?;
let (mut inner_attrs, items, inner_span) =
self.parse_mod(&token::CloseDelim(token::Brace))?;
attrs.append(&mut 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, (Vec<Attribute>, Vec<P<Item>>, Span)> {
let lo = self.token.span;
let attrs = self.parse_inner_attributes()?;
let mut items = vec![];
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.struct_span_err(self.token.span, msg);
err.span_label(self.token.span, "expected item");
return Err(err);
}
}
Ok((attrs, items, lo.to(self.prev_token.span)))
}
}
pub(super) type ItemInfo = (Ident, ItemKind);
impl<'a> Parser<'a> {
pub fn parse_item(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<P<Item>>> {
self.parse_item_(|_| true, force_collect).map(|i| i.map(P))
}
fn parse_item_(
&mut self,
req_name: ReqName,
force_collect: ForceCollect,
) -> PResult<'a, Option<Item>> {
let attrs = self.parse_outer_attributes()?;
self.parse_item_common(attrs, true, false, req_name, force_collect)
}
pub(super) fn parse_item_common(
&mut self,
attrs: AttrWrapper,
mac_allowed: bool,
attrs_allowed: bool,
req_name: ReqName,
force_collect: ForceCollect,
) -> PResult<'a, Option<Item>> {
// Don't use `maybe_whole` so that we have precise control
// over when we bump the parser
if let token::Interpolated(nt) = &self.token.kind {
if let token::NtItem(item) = &**nt {
let mut item = item.clone();
self.bump();
attrs.prepend_to_nt_inner(&mut item.attrs);
return Ok(Some(item.into_inner()));
}
};
let mut unclosed_delims = vec![];
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, req_name);
unclosed_delims.append(&mut this.unclosed_delims);
Ok((item?, TrailingToken::None))
})?;
self.unclosed_delims.append(&mut unclosed_delims);
Ok(item)
}
fn parse_item_common_(
&mut self,
mut attrs: Vec<Attribute>,
mac_allowed: bool,
attrs_allowed: bool,
req_name: ReqName,
) -> 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, req_name)?;
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.
self.error_on_unmatched_vis(&vis);
self.error_on_unmatched_defaultness(def);
if !attrs_allowed {
self.recover_attrs_no_item(&attrs)?;
}
Ok(None)
}
/// Error in-case a non-inherited visibility was parsed but no item followed.
fn error_on_unmatched_vis(&self, vis: &Visibility) {
if let VisibilityKind::Inherited = vis.kind {
return;
}
let vs = pprust::vis_to_string(&vis);
let vs = vs.trim_end();
self.struct_span_err(vis.span, &format!("visibility `{}` is not followed by an item", vs))
.span_label(vis.span, "the visibility")
.help(&format!("you likely meant to define an item, e.g., `{} fn foo() {{}}`", vs))
.emit();
}
/// Error in-case a `default` was parsed but no item followed.
fn error_on_unmatched_defaultness(&self, def: Defaultness) {
if let Defaultness::Default(sp) = def {
self.struct_span_err(sp, "`default` is not followed by an item")
.span_label(sp, "the `default` qualifier")
.note("only `fn`, `const`, `type`, or `impl` items may be prefixed by `default`")
.emit();
}
}
/// 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 {
let msg = format!("{} {} cannot be `default`", kind.article(), kind.descr());
self.struct_span_err(span, &msg)
.span_label(span, "`default` because of this")
.note("only associated `fn`, `const`, and `type` items can be `default`")
.emit();
}
}
/// Parses one of the items allowed by the flags.
fn parse_item_kind(
&mut self,
attrs: &mut Vec<Attribute>,
macros_allowed: bool,
lo: Span,
vis: &Visibility,
def: &mut Defaultness,
req_name: ReqName,
) -> PResult<'a, Option<ItemInfo>> {
let def_final = def == &Defaultness::Final;
let mut def = || mem::replace(def, Defaultness::Final);
let info = if self.eat_keyword(kw::Use) {
// USE ITEM
let tree = self.parse_use_tree()?;
// If wildcard or glob-like brace syntax doesn't have `;`,
// the user may not know `*` or `{}` should be the last.
if let Err(mut e) = self.expect_semi() {
match tree.kind {
UseTreeKind::Glob => {
e.note("the wildcard token must be last on the path").emit();
}
UseTreeKind::Nested(..) => {
e.note("glob-like brace syntax must be last on the path").emit();
}
_ => (),
}
return Err(e);
}
(Ident::invalid(), ItemKind::Use(tree))
} else if self.check_fn_front_matter(def_final) {
// FUNCTION ITEM
let (ident, sig, generics, body) = self.parse_fn(attrs, req_name, lo)?;
(ident, ItemKind::Fn(box FnKind(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();
self.expect_keyword(kw::Extern)?;
self.parse_item_foreign_mod(attrs, unsafety)?
} else if self.is_static_global() {
// STATIC ITEM
self.bump(); // `static`
let m = self.parse_mutability();
let (ident, ty, expr) = self.parse_item_global(Some(m))?;
(ident, ItemKind::Static(ty, m, expr))
} else if let Const::Yes(const_span) = self.parse_constness() {
// 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, ty, expr) = self.parse_item_global(None)?;
(ident, ItemKind::Const(def(), 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.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.eat_keyword(kw::Macro) {
// MACROS 2.0 ITEM
self.parse_item_decl_macro(lo)?
} else if self.is_macro_rules_item() {
// MACRO_RULES ITEM
self.parse_item_macro_rules(vis)?
} else if vis.kind.is_pub() && self.isnt_macro_invocation() {
self.recover_missing_kw_before_item()?;
return Ok(None);
} else if macros_allowed && self.check_path() {
// MACRO INVOCATION ITEM
(Ident::invalid(), ItemKind::MacCall(self.parse_item_macro(vis)?))
} else {
return Ok(None);
};
Ok(Some(info))
}
/// 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_crate_vis() // no: `crate::b`, yes: `crate $item`
|| self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
|| 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`
|| self.is_macro_rules_item() // no: `macro_rules::b`, yes: `macro_rules! mac`
}
/// 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::ModSep)
}
/// 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;
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
);
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",
);
}
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,
);
}
Err(err)
} else {
Ok(())
}
}
/// 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)?; // `!`
let args = self.parse_mac_args()?; // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
self.eat_semi_for_macro_if_needed(&args);
self.complain_if_pub_macro(vis, false);
Ok(MacCall { path, args, prior_type_ascription: self.last_type_ascription })
}
/// 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) = match attrs {
[] => return Ok(()),
[x0 @ xn] | [x0, .., xn] => (x0, xn),
};
let msg = if end.is_doc_comment() {
"expected item after doc comment"
} else {
"expected item after attributes"
};
let mut err = self.struct_span_err(end.span, msg);
if end.is_doc_comment() {
err.span_label(end.span, "this doc comment doesn't document anything");
}
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.
///
/// ```
/// 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,
attrs: &mut Vec<Attribute>,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety();
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();
if let Const::Yes(span) = constness {
self.sess.gated_spans.gate(sym::const_trait_impl, 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.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,
tokens: None,
})
} 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_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
Some(self.mk_ty(self.prev_token.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 = 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.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(box ImplKind {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: Some(trait_ref),
self_ty: ty_second,
items: impl_items,
})
}
None => {
// impl Type
ItemKind::Impl(box ImplKind {
unsafety,
polarity,
defaultness,
constness,
generics,
of_trait: None,
self_ty: ty_first,
items: impl_items,
})
}
};
Ok((Ident::invalid(), item_kind))
}
fn parse_item_list<T>(
&mut self,
attrs: &mut Vec<Attribute>,
mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
) -> PResult<'a, Vec<T>> {
let open_brace_span = self.token.span;
self.expect(&token::OpenDelim(token::Brace))?;
attrs.append(&mut self.parse_inner_attributes()?);
let mut items = Vec::new();
while !self.eat(&token::CloseDelim(token::Brace)) {
if self.recover_doc_comment_before_brace() {
continue;
}
match parse_item(self) {
Ok(None) => {
// We have to bail or we'll potentially never make progress.
let non_item_span = self.token.span;
self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
self.struct_span_err(non_item_span, "non-item in item list")
.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")
.emit();
break;
}
Ok(Some(item)) => items.extend(item),
Err(mut err) => {
self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
err.span_label(open_brace_span, "while parsing this item list starting here")
.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(token::Brace)) {
struct_span_err!(
self.diagnostic(),
self.token.span,
E0584,
"found a documentation comment that doesn't document anything",
)
.span_label(self.token.span, "this doc comment doesn't document anything")
.help(
"doc comments must come before what they document, maybe a \
comment was intended with `//`?",
)
.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 Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
let unsafety = self.parse_unsafety();
// 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_token.span;
let bounds = if had_colon {
self.parse_generic_bounds(Some(self.prev_token.span))?
} 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.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_token.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 let Unsafe::Yes(_) = unsafety {
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)))
} else {
// It's a normal trait.
tps.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 TraitKind(is_auto, unsafety, tps, bounds, items))))
}
}
pub fn parse_impl_item(
&mut self,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
self.parse_assoc_item(|_| true, force_collect)
}
pub fn parse_trait_item(
&mut self,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
self.parse_assoc_item(|edition| edition >= Edition::Edition2018, force_collect)
}
/// Parses associated items.
fn parse_assoc_item(
&mut self,
req_name: ReqName,
force_collect: ForceCollect,
) -> PResult<'a, Option<Option<P<AssocItem>>>> {
Ok(self.parse_item_(req_name, 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(a, _, b) => {
self.struct_span_err(span, "associated `static` items are not allowed")
.emit();
AssocItemKind::Const(Defaultness::Final, a, b)
}
_ => 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:
/// ```
/// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
/// ```
/// The `"type"` has already been eaten.
fn parse_type_alias(&mut self, def: 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(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, ItemKind::TyAlias(box TyAliasKind(def, generics, bounds, default))))
}
/// 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: Vec::new(), span: lo.shrink_to_lo(), tokens: None };
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_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 {
UseTreeKind::Nested(self.parse_use_tree_list()?)
})
}
/// Parses a `UseTreeKind::Nested(list)`.
///
/// ```text
/// 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, Ident> {
match self.token.ident() {
Some((ident @ Ident { name: kw::Underscore, .. }, false)) => {
self.bump();
Ok(ident)
}
_ => self.parse_ident(),
}
}
/// Parses `extern crate` links.
///
/// # Examples
///
/// ```
/// 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 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_token.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,
attrs: &mut Vec<Attribute>,
unsafety: Unsafe,
) -> PResult<'a, ItemInfo> {
let abi = self.parse_abi(); // ABI?
let items = self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No))?;
let module = ast::ForeignMod { unsafety, abi, items };
Ok((Ident::invalid(), 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>>>> {
Ok(self.parse_item_(|_| true, 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(_, a, b) => {
self.error_on_foreign_const(span, ident);
ForeignItemKind::Static(a, Mutability::Not, b)
}
_ => 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: &str) -> Option<T> {
let span = self.sess.source_map().guess_head_span(span);
let descr = kind.descr();
self.struct_span_err(span, &format!("{} is not supported in {}", descr, ctx))
.help(&format!("consider moving the {} out to a nearby module scope", descr))
.emit();
None
}
fn error_on_foreign_const(&self, span: Span, ident: Ident) {
self.struct_span_err(ident.span, "extern items cannot be `const`")
.span_suggestion(
span.with_hi(ident.span.lo()),
"try using a static value",
"static ".to_string(),
Applicability::MachineApplicable,
)
.note("for more information, visit https://doc.rust-lang.org/std/keyword.extern.html")
.emit();
}
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(token::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.struct_span_err(span, "const globals cannot be mutable")
.span_label(span, "cannot be mutable")
.span_suggestion(
const_span,
"you might want to declare a static instead",
"static".to_owned(),
Applicability::MaybeIncorrect,
)
.emit();
}
}
/// Recover on `const impl` with `const` already eaten.
fn recover_const_impl(
&mut self,
const_span: Span,
attrs: &mut Vec<Attribute>,
defaultness: Defaultness,
) -> PResult<'a, ItemInfo> {
let impl_span = self.token.span;
let mut err = self.expected_ident_found();
// 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(mut recovery_error) => {
// Recovery failed, raise the "expected identifier" error
recovery_error.cancel();
return Err(err);
}
};
match impl_info.1 {
ItemKind::Impl(box ImplKind {
of_trait: Some(ref trai), ref mut 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.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 `["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_global(
&mut self,
m: Option<Mutability>,
) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
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.eat(&token::Colon) {
self.parse_ty()?
} else {
self.recover_missing_const_type(id, m)
};
let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
self.expect_semi()?;
Ok((id, ty, expr))
}
/// We were supposed to parse `:` but the `:` was missing.
/// 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, tokens: None })
}
/// 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)))
}
fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
let variant_attrs = self.parse_outer_attributes()?;
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_ident()?;
let struct_def = if this.check(&token::OpenDelim(token::Brace)) {
// Parse a struct variant.
let (fields, recovered) = this.parse_record_struct_body()?;
VariantData::Struct(fields, recovered)
} else if this.check(&token::OpenDelim(token::Paren)) {
VariantData::Tuple(this.parse_tuple_struct_body()?, DUMMY_NODE_ID)
} else {
VariantData::Unit(DUMMY_NODE_ID)
};
let disr_expr =
if this.eat(&token::Eq) { Some(this.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(this.prev_token.span),
is_placeholder: false,
};
Ok((Some(vr), TrailingToken::MaybeComma))
},
)
}
/// 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)))
}
/// 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)))
}
fn parse_record_struct_body(&mut self) -> PResult<'a, (Vec<FieldDef>, /* 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_field_def().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<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 lo = p.token.span;
let vis = p.parse_visibility(FollowedByType::Yes)?;
let ty = p.parse_ty()?;
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) -> PResult<'a, FieldDef> {
let attrs = self.parse_outer_attributes()?;
self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
let lo = this.token.span;
let vis = this.parse_visibility(FollowedByType::No)?;
Ok((this.parse_single_struct_field(lo, vis, attrs)?, TrailingToken::None))
})
}
/// Parses a structure field declaration.
fn parse_single_struct_field(
&mut self,
lo: Span,
vis: Visibility,
attrs: Vec<Attribute>,
) -> PResult<'a, FieldDef> {
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_token.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 && comma_after_doc_seen {
seen_comma = true;
}
if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
err.emit();
} else {
if !seen_comma {
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_token.span.shrink_to_hi();
let mut err = self.struct_span_err(
sp,
&format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
);
// Try to recover extra trailing angle brackets
let mut recovered = false;
if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
if let Some(last_segment) = segments.last() {
recovered = self.check_trailing_angle_brackets(
last_segment,
&[&token::Comma, &token::CloseDelim(token::Brace)],
);
if recovered {
// 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
err.cancel();
}
}
}
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();
recovered = true;
}
if recovered {
// Make sure an error was emitted (either by recovering an angle bracket,
// or by finding an identifier as the next token), since we're
// going to continue parsing
assert!(self.sess.span_diagnostic.has_errors());
} 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, FieldDef> {
let name = self.parse_ident_common(false)?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
Ok(FieldDef {
span: lo.to(self.prev_token.span),
ident: Some(name),
vis,
id: DUMMY_NODE_ID,
ty,
attrs,
is_placeholder: false,
})
}
/// Parses a declarative macro 2.0 definition.
/// The `macro` keyword has already been parsed.
/// ```
/// 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(token::Brace)) {
self.parse_mac_args()? // `MacBody`
} else if self.check(&token::OpenDelim(token::Paren)) {
let params = self.parse_token_tree(); // `MacParams`
let pspan = params.span();
if !self.check(&token::OpenDelim(token::Brace)) {
return self.unexpected();
}
let body = self.parse_token_tree(); // `MacBody`
// Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
let bspan = body.span();
let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
let tokens = TokenStream::new(vec![params.into(), arrow.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();
};
self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: false })))
}
/// Is this unambiguously the start of a `macro_rules! foo` item definition?
fn is_macro_rules_item(&mut self) -> bool {
self.check_keyword(kw::MacroRules)
&& self.look_ahead(1, |t| *t == token::Not)
&& self.look_ahead(2, |t| t.is_ident())
}
/// Parses a `macro_rules! foo { ... }` declarative macro.
fn parse_item_macro_rules(&mut self, vis: &Visibility) -> PResult<'a, ItemInfo> {
self.expect_keyword(kw::MacroRules)?; // `macro_rules`
self.expect(&token::Not)?; // `!`
let ident = self.parse_ident()?;
let body = self.parse_mac_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 {
let msg = format!("can't qualify macro_rules invocation with `{}`", vstr);
self.struct_span_err(vis.span, &msg)
.span_suggestion(
vis.span,
"try exporting the macro",
"#[macro_export]".to_owned(),
Applicability::MaybeIncorrect, // speculative
)
.emit();
} else {
self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
.span_suggestion(
vis.span,
"remove the visibility",
String::new(),
Applicability::MachineApplicable,
)
.help(&format!("try adjusting the macro to put `{}` inside the invocation", vstr))
.emit();
}
}
fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
if args.need_semicolon() && !self.eat(&token::Semi) {
self.report_invalid_macro_expansion_item(args);
}
}
fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
let span = args.span().expect("undelimited macro call");
let mut err = self.struct_span_err(
span,
"macros that expand to items must be delimited with braces or followed by a semicolon",
);
if self.unclosed_delims.is_empty() {
let DelimSpan { open, close } = match args {
MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
MacArgs::Delimited(dspan, ..) => *dspan,
};
err.multipart_suggestion(
"change the delimiters to curly braces",
vec![(open, "{".to_string()), (close, '}'.to_string())],
Applicability::MaybeIncorrect,
);
} else {
err.span_suggestion(
span,
"change the delimiters to curly braces",
" { /* items */ }".to_string(),
Applicability::HasPlaceholders,
);
}
err.span_suggestion(
span.shrink_to_hi(),
"add a semicolon",
';'.to_string(),
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.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)
}
}
/// 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.
type ReqName = fn(Edition) -> 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 Vec<Attribute>,
req_name: ReqName,
sig_lo: Span,
) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
let header = self.parse_fn_front_matter()?; // `const ... fn`
let ident = self.parse_ident()?; // `foo`
let mut generics = self.parse_generics()?; // `<'a, T, ...>`
let decl = self.parse_fn_decl(req_name, AllowPlus::Yes, RecoverReturnSign::Yes)?; // `(p: u8, ...)`
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)?; // `;` 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 Vec<Attribute>,
ident: &Ident,
sig_hi: &mut Span,
) -> PResult<'a, Option<P<Block>>> {
let (inner_attrs, body) = if self.eat(&token::Semi) {
// Include the trailing semicolon in the span of the signature
*sig_hi = self.prev_token.span;
(Vec::new(), None)
} else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
self.parse_inner_attrs_and_block().map(|(attrs, body)| (attrs, Some(body)))?
} else if self.token.kind == token::Eq {
// Recover `fn foo() = $expr;`.
self.bump(); // `=`
let eq_sp = self.prev_token.span;
let _ = self.parse_expr()?;
self.expect_semi()?; // `;`
let span = eq_sp.to(self.prev_token.span);
self.struct_span_err(span, "function body cannot be `= expression;`")
.multipart_suggestion(
"surround the expression with `{` and `}` instead of `=` and `;`",
vec![(eq_sp, "{".to_string()), (self.prev_token.span, " }".to_string())],
Applicability::MachineApplicable,
)
.emit();
(Vec::new(), Some(self.mk_block_err(span)))
} else {
if let Err(mut err) =
self.expected_one_of_not_found(&[], &[token::Semi, token::OpenDelim(token::Brace)])
{
if self.token.kind == token::CloseDelim(token::Brace) {
// The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
// the AST for typechecking.
err.span_label(ident.span, "while parsing this `fn`");
err.emit();
(Vec::new(), None)
} else {
return Err(err);
}
} else {
unreachable!()
}
};
attrs.extend(inner_attrs);
Ok(body)
}
/// Is the current token the start of an `FnHeader` / not a valid parse?
///
/// `check_pub` adds additional `pub` to the checks in case users place it
/// wrongly, can be used to ensure `pub` never comes after `default`.
pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
// We use an over-approximation here.
// `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
// `pub` is added in case users got confused with the ordering like `async pub fn`,
// only if it wasn't preceeded by `default` as `default pub` is invalid.
let quals: &[Symbol] = if check_pub {
&[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
} else {
&[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
};
self.check_keyword(kw::Fn) // Definitely an `fn`.
// `$qual fn` or `$qual $qual`:
|| quals.iter().any(|&kw| self.check_keyword(kw))
&& self.look_ahead(1, |t| {
// `$qual fn`, e.g. `const fn` or `async fn`.
t.is_keyword(kw::Fn)
// 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()
// Rule out unsafe extern block.
&& !self.is_unsafe_foreign_mod())
})
// `extern ABI fn`
|| self.check_keyword(kw::Extern)
&& self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
&& self.look_ahead(2, |t| t.is_keyword(kw::Fn))
}
/// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
/// up to and including the `fn` keyword. The formal grammar is:
///
/// ```
/// Extern = "extern" StringLit? ;
/// FnQual = "const"? "async"? "unsafe"? Extern? ;
/// FnFrontMatter = FnQual "fn" ;
/// ```
pub(super) fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
let sp_start = self.token.span;
let constness = self.parse_constness();
let asyncness = self.parse_asyncness();
let unsafety = self.parse_unsafety();
let ext = self.parse_extern();
if let Async::Yes { span, .. } = asyncness {
self.ban_async_in_2015(span);
}
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.
match self.expect_one_of(&[], &[]) {
Ok(true) => {}
Ok(false) => unreachable!(),
Err(mut err) => {
// Recover incorrect visibility order such as `async pub`.
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 vis = self.parse_visibility(FollowedByType::No)?;
let vs = pprust::vis_to_string(&vis);
let vs = vs.trim_end();
err.span_suggestion(
sp_start.to(self.prev_token.span),
&format!("visibility `{}` must come before `{}`", vs, snippet),
format!("{} {}", vs, snippet),
Applicability::MachineApplicable,
);
}
}
return Err(err);
}
}
}
Ok(FnHeader { constness, unsafety, asyncness, ext })
}
/// We are parsing `async fn`. If we are on Rust 2015, emit an error.
fn ban_async_in_2015(&self, span: Span) {
if span.rust_2015() {
let diag = self.diagnostic();
struct_span_err!(diag, span, E0670, "`async fn` is not permitted in Rust 2015")
.span_label(span, "to use `async fn`, switch to Rust 2018 or later")
.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION))
.note("for more on editions, read https://doc.rust-lang.org/edition-guide")
.emit();
}
}
/// 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.
fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
let mut first_param = true;
// Parse the arguments, starting out with `self` being allowed...
let (mut params, _) = self.parse_paren_comma_seq(|p| {
let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
e.emit();
let lo = p.prev_token.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::Empty, lo.to(p.prev_token.span))))
});
// ...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.into();
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.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)
{
err.emit();
Ok((dummy_arg(ident), 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.clone();
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(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 = this.unexpected();
}
match ty {
Ok(ty) => {
let ident = Ident::new(kw::Empty, this.prev_token.span);
let bm = BindingMode::ByValue(Mutability::Not);
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(mut err) => {
err.cancel();
*this = parser_snapshot_before_ty;
this.recover_arg_parse()?
}
}
};
let span = lo.until(this.token.span);
Ok((
Param {
attrs: attrs.into(),
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, false)) => {
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::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_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| {
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_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(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",
}
}
}