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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /compiler/rustc_parse/src/parser
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_parse/src/parser')
-rw-r--r--compiler/rustc_parse/src/parser/attr.rs444
-rw-r--r--compiler/rustc_parse/src/parser/attr_wrapper.rs464
-rw-r--r--compiler/rustc_parse/src/parser/diagnostics.rs2740
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs3288
-rw-r--r--compiler/rustc_parse/src/parser/generics.rs350
-rw-r--r--compiler/rustc_parse/src/parser/item.rs2426
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs1481
-rw-r--r--compiler/rustc_parse/src/parser/nonterminal.rs203
-rw-r--r--compiler/rustc_parse/src/parser/pat.rs1151
-rw-r--r--compiler/rustc_parse/src/parser/path.rs754
-rw-r--r--compiler/rustc_parse/src/parser/stmt.rs648
-rw-r--r--compiler/rustc_parse/src/parser/ty.rs891
12 files changed, 14840 insertions, 0 deletions
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
new file mode 100644
index 000000000..acdbddf40
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -0,0 +1,444 @@
+use super::{AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, PathStyle};
+use rustc_ast as ast;
+use rustc_ast::attr;
+use rustc_ast::token::{self, Delimiter, Nonterminal};
+use rustc_ast_pretty::pprust;
+use rustc_errors::{error_code, Diagnostic, PResult};
+use rustc_span::{sym, BytePos, Span};
+use std::convert::TryInto;
+
+use tracing::debug;
+
+// Public for rustfmt usage
+#[derive(Debug)]
+pub enum InnerAttrPolicy<'a> {
+ Permitted,
+ Forbidden { reason: &'a str, saw_doc_comment: bool, prev_outer_attr_sp: Option<Span> },
+}
+
+const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
+ permitted in this context";
+
+pub(super) const DEFAULT_INNER_ATTR_FORBIDDEN: InnerAttrPolicy<'_> = InnerAttrPolicy::Forbidden {
+ reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG,
+ saw_doc_comment: false,
+ prev_outer_attr_sp: None,
+};
+
+enum OuterAttributeType {
+ DocComment,
+ DocBlockComment,
+ Attribute,
+}
+
+impl<'a> Parser<'a> {
+ /// Parses attributes that appear before an item.
+ pub(super) fn parse_outer_attributes(&mut self) -> PResult<'a, AttrWrapper> {
+ let mut outer_attrs: Vec<ast::Attribute> = Vec::new();
+ let mut just_parsed_doc_comment = false;
+ let start_pos = self.token_cursor.num_next_calls;
+ loop {
+ let attr = if self.check(&token::Pound) {
+ let prev_outer_attr_sp = outer_attrs.last().map(|attr| attr.span);
+
+ let inner_error_reason = if just_parsed_doc_comment {
+ "an inner attribute is not permitted following an outer doc comment"
+ } else if prev_outer_attr_sp.is_some() {
+ "an inner attribute is not permitted following an outer attribute"
+ } else {
+ DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
+ };
+ let inner_parse_policy = InnerAttrPolicy::Forbidden {
+ reason: inner_error_reason,
+ saw_doc_comment: just_parsed_doc_comment,
+ prev_outer_attr_sp,
+ };
+ just_parsed_doc_comment = false;
+ Some(self.parse_attribute(inner_parse_policy)?)
+ } else if let token::DocComment(comment_kind, attr_style, data) = self.token.kind {
+ if attr_style != ast::AttrStyle::Outer {
+ let span = self.token.span;
+ let mut err = self.sess.span_diagnostic.struct_span_err_with_code(
+ span,
+ "expected outer doc comment",
+ error_code!(E0753),
+ );
+ if let Some(replacement_span) = self.annotate_following_item_if_applicable(
+ &mut err,
+ span,
+ match comment_kind {
+ token::CommentKind::Line => OuterAttributeType::DocComment,
+ token::CommentKind::Block => OuterAttributeType::DocBlockComment,
+ },
+ ) {
+ err.note(
+ "inner doc comments like this (starting with `//!` or `/*!`) can \
+ only appear before items",
+ );
+ err.span_suggestion_verbose(
+ replacement_span,
+ "you might have meant to write a regular comment",
+ "",
+ rustc_errors::Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ }
+ self.bump();
+ just_parsed_doc_comment = true;
+ // Always make an outer attribute - this allows us to recover from a misplaced
+ // inner attribute.
+ Some(attr::mk_doc_comment(
+ comment_kind,
+ ast::AttrStyle::Outer,
+ data,
+ self.prev_token.span,
+ ))
+ } else {
+ None
+ };
+
+ if let Some(attr) = attr {
+ if attr.style == ast::AttrStyle::Outer {
+ outer_attrs.push(attr);
+ }
+ } else {
+ break;
+ }
+ }
+ Ok(AttrWrapper::new(outer_attrs.into(), start_pos))
+ }
+
+ /// Matches `attribute = # ! [ meta_item ]`.
+ /// `inner_parse_policy` prescribes how to handle inner attributes.
+ // Public for rustfmt usage.
+ pub fn parse_attribute(
+ &mut self,
+ inner_parse_policy: InnerAttrPolicy<'_>,
+ ) -> PResult<'a, ast::Attribute> {
+ debug!(
+ "parse_attribute: inner_parse_policy={:?} self.token={:?}",
+ inner_parse_policy, self.token
+ );
+ let lo = self.token.span;
+ // Attributes can't have attributes of their own [Editor's note: not with that attitude]
+ self.collect_tokens_no_attrs(|this| {
+ if this.eat(&token::Pound) {
+ let style = if this.eat(&token::Not) {
+ ast::AttrStyle::Inner
+ } else {
+ ast::AttrStyle::Outer
+ };
+
+ this.expect(&token::OpenDelim(Delimiter::Bracket))?;
+ let item = this.parse_attr_item(false)?;
+ this.expect(&token::CloseDelim(Delimiter::Bracket))?;
+ let attr_sp = lo.to(this.prev_token.span);
+
+ // Emit error if inner attribute is encountered and forbidden.
+ if style == ast::AttrStyle::Inner {
+ this.error_on_forbidden_inner_attr(attr_sp, inner_parse_policy);
+ }
+
+ Ok(attr::mk_attr_from_item(item, None, style, attr_sp))
+ } else {
+ let token_str = pprust::token_to_string(&this.token);
+ let msg = &format!("expected `#`, found `{token_str}`");
+ Err(this.struct_span_err(this.token.span, msg))
+ }
+ })
+ }
+
+ fn annotate_following_item_if_applicable(
+ &self,
+ err: &mut Diagnostic,
+ span: Span,
+ attr_type: OuterAttributeType,
+ ) -> Option<Span> {
+ let mut snapshot = self.create_snapshot_for_diagnostic();
+ let lo = span.lo()
+ + BytePos(match attr_type {
+ OuterAttributeType::Attribute => 1,
+ _ => 2,
+ });
+ let hi = lo + BytePos(1);
+ let replacement_span = span.with_lo(lo).with_hi(hi);
+ if let OuterAttributeType::DocBlockComment | OuterAttributeType::DocComment = attr_type {
+ snapshot.bump();
+ }
+ loop {
+ // skip any other attributes, we want the item
+ if snapshot.token.kind == token::Pound {
+ if let Err(err) = snapshot.parse_attribute(InnerAttrPolicy::Permitted) {
+ err.cancel();
+ return Some(replacement_span);
+ }
+ } else {
+ break;
+ }
+ }
+ match snapshot.parse_item_common(
+ AttrWrapper::empty(),
+ true,
+ false,
+ FnParseMode { req_name: |_| true, req_body: true },
+ ForceCollect::No,
+ ) {
+ Ok(Some(item)) => {
+ let attr_name = match attr_type {
+ OuterAttributeType::Attribute => "attribute",
+ _ => "doc comment",
+ };
+ err.span_label(
+ item.span,
+ &format!("the inner {} doesn't annotate this {}", attr_name, item.kind.descr()),
+ );
+ err.span_suggestion_verbose(
+ replacement_span,
+ &format!(
+ "to annotate the {}, change the {} from inner to outer style",
+ item.kind.descr(),
+ attr_name
+ ),
+ match attr_type {
+ OuterAttributeType::Attribute => "",
+ OuterAttributeType::DocBlockComment => "*",
+ OuterAttributeType::DocComment => "/",
+ },
+ rustc_errors::Applicability::MachineApplicable,
+ );
+ return None;
+ }
+ Err(item_err) => {
+ item_err.cancel();
+ }
+ Ok(None) => {}
+ }
+ Some(replacement_span)
+ }
+
+ pub(super) fn error_on_forbidden_inner_attr(&self, attr_sp: Span, policy: InnerAttrPolicy<'_>) {
+ if let InnerAttrPolicy::Forbidden { reason, saw_doc_comment, prev_outer_attr_sp } = policy {
+ let prev_outer_attr_note =
+ if saw_doc_comment { "previous doc comment" } else { "previous outer attribute" };
+
+ let mut diag = self.struct_span_err(attr_sp, reason);
+
+ if let Some(prev_outer_attr_sp) = prev_outer_attr_sp {
+ diag.span_label(attr_sp, "not permitted following an outer attribute")
+ .span_label(prev_outer_attr_sp, prev_outer_attr_note);
+ }
+
+ diag.note(
+ "inner attributes, like `#![no_std]`, annotate the item enclosing them, and \
+ are usually found at the beginning of source files",
+ );
+ if self
+ .annotate_following_item_if_applicable(
+ &mut diag,
+ attr_sp,
+ OuterAttributeType::Attribute,
+ )
+ .is_some()
+ {
+ diag.note("outer attributes, like `#[test]`, annotate the item following them");
+ };
+ diag.emit();
+ }
+ }
+
+ /// Parses an inner part of an attribute (the path and following tokens).
+ /// The tokens must be either a delimited token stream, or empty token stream,
+ /// or the "legacy" key-value form.
+ /// PATH `(` TOKEN_STREAM `)`
+ /// PATH `[` TOKEN_STREAM `]`
+ /// PATH `{` TOKEN_STREAM `}`
+ /// PATH
+ /// PATH `=` UNSUFFIXED_LIT
+ /// The delimiters or `=` are still put into the resulting token stream.
+ pub fn parse_attr_item(&mut self, capture_tokens: bool) -> PResult<'a, ast::AttrItem> {
+ let item = match self.token.kind {
+ token::Interpolated(ref nt) => match **nt {
+ Nonterminal::NtMeta(ref item) => Some(item.clone().into_inner()),
+ _ => None,
+ },
+ _ => None,
+ };
+ Ok(if let Some(item) = item {
+ self.bump();
+ item
+ } else {
+ let do_parse = |this: &mut Self| {
+ let path = this.parse_path(PathStyle::Mod)?;
+ let args = this.parse_attr_args()?;
+ Ok(ast::AttrItem { path, args, tokens: None })
+ };
+ // Attr items don't have attributes
+ if capture_tokens { self.collect_tokens_no_attrs(do_parse) } else { do_parse(self) }?
+ })
+ }
+
+ /// Parses attributes that appear after the opening of an item. These should
+ /// be preceded by an exclamation mark, but we accept and warn about one
+ /// terminated by a semicolon.
+ ///
+ /// Matches `inner_attrs*`.
+ pub(crate) fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
+ let mut attrs: Vec<ast::Attribute> = vec![];
+ loop {
+ let start_pos: u32 = self.token_cursor.num_next_calls.try_into().unwrap();
+ // Only try to parse if it is an inner attribute (has `!`).
+ let attr = if self.check(&token::Pound) && self.look_ahead(1, |t| t == &token::Not) {
+ Some(self.parse_attribute(InnerAttrPolicy::Permitted)?)
+ } else if let token::DocComment(comment_kind, attr_style, data) = self.token.kind {
+ if attr_style == ast::AttrStyle::Inner {
+ self.bump();
+ Some(attr::mk_doc_comment(comment_kind, attr_style, data, self.prev_token.span))
+ } else {
+ None
+ }
+ } else {
+ None
+ };
+ if let Some(attr) = attr {
+ let end_pos: u32 = self.token_cursor.num_next_calls.try_into().unwrap();
+ // If we are currently capturing tokens, mark the location of this inner attribute.
+ // If capturing ends up creating a `LazyTokenStream`, we will include
+ // this replace range with it, removing the inner attribute from the final
+ // `AttrAnnotatedTokenStream`. Inner attributes are stored in the parsed AST note.
+ // During macro expansion, they are selectively inserted back into the
+ // token stream (the first inner attribute is removed each time we invoke the
+ // corresponding macro).
+ let range = start_pos..end_pos;
+ if let Capturing::Yes = self.capture_state.capturing {
+ self.capture_state.inner_attr_ranges.insert(attr.id, (range, vec![]));
+ }
+ attrs.push(attr);
+ } else {
+ break;
+ }
+ }
+ Ok(attrs)
+ }
+
+ pub(crate) fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
+ let lit = self.parse_lit()?;
+ debug!("checking if {:?} is unusuffixed", lit);
+
+ if !lit.kind.is_unsuffixed() {
+ self.struct_span_err(lit.span, "suffixed literals are not allowed in attributes")
+ .help(
+ "instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), \
+ use an unsuffixed version (`1`, `1.0`, etc.)",
+ )
+ .emit();
+ }
+
+ Ok(lit)
+ }
+
+ /// Parses `cfg_attr(pred, attr_item_list)` where `attr_item_list` is comma-delimited.
+ pub fn parse_cfg_attr(&mut self) -> PResult<'a, (ast::MetaItem, Vec<(ast::AttrItem, Span)>)> {
+ let cfg_predicate = self.parse_meta_item()?;
+ self.expect(&token::Comma)?;
+
+ // Presumably, the majority of the time there will only be one attr.
+ let mut expanded_attrs = Vec::with_capacity(1);
+ while self.token.kind != token::Eof {
+ let lo = self.token.span;
+ let item = self.parse_attr_item(true)?;
+ expanded_attrs.push((item, lo.to(self.prev_token.span)));
+ if !self.eat(&token::Comma) {
+ break;
+ }
+ }
+
+ Ok((cfg_predicate, expanded_attrs))
+ }
+
+ /// Matches `COMMASEP(meta_item_inner)`.
+ pub(crate) fn parse_meta_seq_top(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
+ // Presumably, the majority of the time there will only be one attr.
+ let mut nmis = Vec::with_capacity(1);
+ while self.token.kind != token::Eof {
+ nmis.push(self.parse_meta_item_inner()?);
+ if !self.eat(&token::Comma) {
+ break;
+ }
+ }
+ Ok(nmis)
+ }
+
+ /// Matches the following grammar (per RFC 1559).
+ /// ```ebnf
+ /// meta_item : PATH ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
+ /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
+ /// ```
+ pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
+ let nt_meta = match self.token.kind {
+ token::Interpolated(ref nt) => match **nt {
+ token::NtMeta(ref e) => Some(e.clone()),
+ _ => None,
+ },
+ _ => None,
+ };
+
+ if let Some(item) = nt_meta {
+ return match item.meta(item.path.span) {
+ Some(meta) => {
+ self.bump();
+ Ok(meta)
+ }
+ None => self.unexpected(),
+ };
+ }
+
+ let lo = self.token.span;
+ let path = self.parse_path(PathStyle::Mod)?;
+ let kind = self.parse_meta_item_kind()?;
+ let span = lo.to(self.prev_token.span);
+ Ok(ast::MetaItem { path, kind, span })
+ }
+
+ pub(crate) fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
+ Ok(if self.eat(&token::Eq) {
+ ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
+ } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ // Matches `meta_seq = ( COMMASEP(meta_item_inner) )`.
+ let (list, _) = self.parse_paren_comma_seq(|p| p.parse_meta_item_inner())?;
+ ast::MetaItemKind::List(list)
+ } else {
+ ast::MetaItemKind::Word
+ })
+ }
+
+ /// Matches `meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;`.
+ fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
+ match self.parse_unsuffixed_lit() {
+ Ok(lit) => return Ok(ast::NestedMetaItem::Literal(lit)),
+ Err(err) => err.cancel(),
+ }
+
+ match self.parse_meta_item() {
+ Ok(mi) => return Ok(ast::NestedMetaItem::MetaItem(mi)),
+ Err(err) => err.cancel(),
+ }
+
+ let found = pprust::token_to_string(&self.token);
+ let msg = format!("expected unsuffixed literal or identifier, found `{found}`");
+ Err(self.struct_span_err(self.token.span, &msg))
+ }
+}
+
+pub fn maybe_needs_tokens(attrs: &[ast::Attribute]) -> bool {
+ // One of the attributes may either itself be a macro,
+ // or expand to macro attributes (`cfg_attr`).
+ attrs.iter().any(|attr| {
+ if attr.is_doc_comment() {
+ return false;
+ }
+ attr.ident().map_or(true, |ident| {
+ ident.name == sym::cfg_attr || !rustc_feature::is_builtin_attr_name(ident.name)
+ })
+ })
+}
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
new file mode 100644
index 000000000..6c750ff42
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -0,0 +1,464 @@
+use super::{Capturing, FlatToken, ForceCollect, Parser, ReplaceRange, TokenCursor, TrailingToken};
+use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::tokenstream::{AttrAnnotatedTokenStream, AttributesData, CreateTokenStream};
+use rustc_ast::tokenstream::{AttrAnnotatedTokenTree, DelimSpan, LazyTokenStream, Spacing};
+use rustc_ast::{self as ast};
+use rustc_ast::{AttrVec, Attribute, HasAttrs, HasTokens};
+use rustc_errors::PResult;
+use rustc_span::{sym, Span};
+
+use std::convert::TryInto;
+use std::ops::Range;
+
+/// A wrapper type to ensure that the parser handles outer attributes correctly.
+/// When we parse outer attributes, we need to ensure that we capture tokens
+/// for the attribute target. This allows us to perform cfg-expansion on
+/// a token stream before we invoke a derive proc-macro.
+///
+/// This wrapper prevents direct access to the underlying `Vec<ast::Attribute>`.
+/// Parsing code can only get access to the underlying attributes
+/// by passing an `AttrWrapper` to `collect_tokens_trailing_tokens`.
+/// This makes it difficult to accidentally construct an AST node
+/// (which stores a `Vec<ast::Attribute>`) without first collecting tokens.
+///
+/// This struct has its own module, to ensure that the parser code
+/// cannot directly access the `attrs` field
+#[derive(Debug, Clone)]
+pub struct AttrWrapper {
+ attrs: AttrVec,
+ // The start of the outer attributes in the token cursor.
+ // This allows us to create a `ReplaceRange` for the entire attribute
+ // target, including outer attributes.
+ start_pos: usize,
+}
+
+// This struct is passed around very frequently,
+// so make sure it doesn't accidentally get larger
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(AttrWrapper, 16);
+
+impl AttrWrapper {
+ pub(super) fn new(attrs: AttrVec, start_pos: usize) -> AttrWrapper {
+ AttrWrapper { attrs, start_pos }
+ }
+ pub fn empty() -> AttrWrapper {
+ AttrWrapper { attrs: AttrVec::new(), start_pos: usize::MAX }
+ }
+ // FIXME: Delay span bug here?
+ pub(crate) fn take_for_recovery(self) -> AttrVec {
+ self.attrs
+ }
+
+ // FIXME: require passing an NT to prevent misuse of this method
+ pub(crate) fn prepend_to_nt_inner(self, attrs: &mut Vec<Attribute>) {
+ let mut self_attrs: Vec<_> = self.attrs.into();
+ std::mem::swap(attrs, &mut self_attrs);
+ attrs.extend(self_attrs);
+ }
+
+ pub fn is_empty(&self) -> bool {
+ self.attrs.is_empty()
+ }
+
+ pub fn maybe_needs_tokens(&self) -> bool {
+ crate::parser::attr::maybe_needs_tokens(&self.attrs)
+ }
+}
+
+/// Returns `true` if `attrs` contains a `cfg` or `cfg_attr` attribute
+fn has_cfg_or_cfg_attr(attrs: &[Attribute]) -> bool {
+ // NOTE: Builtin attributes like `cfg` and `cfg_attr` cannot be renamed via imports.
+ // Therefore, the absence of a literal `cfg` or `cfg_attr` guarantees that
+ // we don't need to do any eager expansion.
+ attrs.iter().any(|attr| {
+ attr.ident().map_or(false, |ident| ident.name == sym::cfg || ident.name == sym::cfg_attr)
+ })
+}
+
+// Produces a `TokenStream` on-demand. Using `cursor_snapshot`
+// and `num_calls`, we can reconstruct the `TokenStream` seen
+// by the callback. This allows us to avoid producing a `TokenStream`
+// if it is never needed - for example, a captured `macro_rules!`
+// argument that is never passed to a proc macro.
+// In practice token stream creation happens rarely compared to
+// calls to `collect_tokens` (see some statistics in #78736),
+// so we are doing as little up-front work as possible.
+//
+// This also makes `Parser` very cheap to clone, since
+// there is no intermediate collection buffer to clone.
+#[derive(Clone)]
+struct LazyTokenStreamImpl {
+ start_token: (Token, Spacing),
+ cursor_snapshot: TokenCursor,
+ num_calls: usize,
+ break_last_token: bool,
+ replace_ranges: Box<[ReplaceRange]>,
+}
+
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(LazyTokenStreamImpl, 144);
+
+impl CreateTokenStream for LazyTokenStreamImpl {
+ fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
+ // The token produced by the final call to `{,inlined_}next` was not
+ // actually consumed by the callback. The combination of chaining the
+ // initial token and using `take` produces the desired result - we
+ // produce an empty `TokenStream` if no calls were made, and omit the
+ // final token otherwise.
+ let mut cursor_snapshot = self.cursor_snapshot.clone();
+ let tokens =
+ std::iter::once((FlatToken::Token(self.start_token.0.clone()), self.start_token.1))
+ .chain((0..self.num_calls).map(|_| {
+ let token = cursor_snapshot.next(cursor_snapshot.desugar_doc_comments);
+ (FlatToken::Token(token.0), token.1)
+ }))
+ .take(self.num_calls);
+
+ if !self.replace_ranges.is_empty() {
+ let mut tokens: Vec<_> = tokens.collect();
+ let mut replace_ranges = self.replace_ranges.clone();
+ replace_ranges.sort_by_key(|(range, _)| range.start);
+
+ #[cfg(debug_assertions)]
+ {
+ for [(range, tokens), (next_range, next_tokens)] in replace_ranges.array_windows() {
+ assert!(
+ range.end <= next_range.start || range.end >= next_range.end,
+ "Replace ranges should either be disjoint or nested: ({:?}, {:?}) ({:?}, {:?})",
+ range,
+ tokens,
+ next_range,
+ next_tokens,
+ );
+ }
+ }
+
+ // Process the replace ranges, starting from the highest start
+ // position and working our way back. If have tokens like:
+ //
+ // `#[cfg(FALSE)]` struct Foo { #[cfg(FALSE)] field: bool }`
+ //
+ // Then we will generate replace ranges for both
+ // the `#[cfg(FALSE)] field: bool` and the entire
+ // `#[cfg(FALSE)]` struct Foo { #[cfg(FALSE)] field: bool }`
+ //
+ // By starting processing from the replace range with the greatest
+ // start position, we ensure that any replace range which encloses
+ // another replace range will capture the *replaced* tokens for the inner
+ // range, not the original tokens.
+ for (range, new_tokens) in replace_ranges.iter().rev() {
+ assert!(!range.is_empty(), "Cannot replace an empty range: {:?}", range);
+ // Replace ranges are only allowed to decrease the number of tokens.
+ assert!(
+ range.len() >= new_tokens.len(),
+ "Range {:?} has greater len than {:?}",
+ range,
+ new_tokens
+ );
+
+ // Replace any removed tokens with `FlatToken::Empty`.
+ // This keeps the total length of `tokens` constant throughout the
+ // replacement process, allowing us to use all of the `ReplaceRanges` entries
+ // without adjusting indices.
+ let filler = std::iter::repeat((FlatToken::Empty, Spacing::Alone))
+ .take(range.len() - new_tokens.len());
+
+ tokens.splice(
+ (range.start as usize)..(range.end as usize),
+ new_tokens.clone().into_iter().chain(filler),
+ );
+ }
+ make_token_stream(tokens.into_iter(), self.break_last_token)
+ } else {
+ make_token_stream(tokens, self.break_last_token)
+ }
+ }
+}
+
+impl<'a> Parser<'a> {
+ /// Records all tokens consumed by the provided callback,
+ /// including the current token. These tokens are collected
+ /// into a `LazyTokenStream`, and returned along with the result
+ /// of the callback.
+ ///
+ /// Note: If your callback consumes an opening delimiter
+ /// (including the case where you call `collect_tokens`
+ /// when the current token is an opening delimiter),
+ /// you must also consume the corresponding closing delimiter.
+ ///
+ /// That is, you can consume
+ /// `something ([{ }])` or `([{}])`, but not `([{}]`
+ ///
+ /// This restriction shouldn't be an issue in practice,
+ /// since this function is used to record the tokens for
+ /// a parsed AST item, which always has matching delimiters.
+ pub fn collect_tokens_trailing_token<R: HasAttrs + HasTokens>(
+ &mut self,
+ attrs: AttrWrapper,
+ force_collect: ForceCollect,
+ f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, (R, TrailingToken)>,
+ ) -> PResult<'a, R> {
+ // We only bail out when nothing could possibly observe the collected tokens:
+ // 1. We cannot be force collecting tokens (since force-collecting requires tokens
+ // by definition
+ if matches!(force_collect, ForceCollect::No)
+ // None of our outer attributes can require tokens (e.g. a proc-macro)
+ && !attrs.maybe_needs_tokens()
+ // If our target supports custom inner attributes, then we cannot bail
+ // out early, since we may need to capture tokens for a custom inner attribute
+ // invocation.
+ && !R::SUPPORTS_CUSTOM_INNER_ATTRS
+ // Never bail out early in `capture_cfg` mode, since there might be `#[cfg]`
+ // or `#[cfg_attr]` attributes.
+ && !self.capture_cfg
+ {
+ return Ok(f(self, attrs.attrs.into())?.0);
+ }
+
+ let start_token = (self.token.clone(), self.token_spacing);
+ let cursor_snapshot = self.token_cursor.clone();
+
+ let has_outer_attrs = !attrs.attrs.is_empty();
+ let prev_capturing = std::mem::replace(&mut self.capture_state.capturing, Capturing::Yes);
+ let replace_ranges_start = self.capture_state.replace_ranges.len();
+
+ let ret = f(self, attrs.attrs.into());
+
+ self.capture_state.capturing = prev_capturing;
+
+ let (mut ret, trailing) = ret?;
+
+ // When we're not in `capture-cfg` mode, then bail out early if:
+ // 1. Our target doesn't support tokens at all (e.g we're parsing an `NtIdent`)
+ // so there's nothing for us to do.
+ // 2. Our target already has tokens set (e.g. we've parsed something
+ // like `#[my_attr] $item`. The actual parsing code takes care of prepending
+ // any attributes to the nonterminal, so we don't need to modify the
+ // already captured tokens.
+ // Note that this check is independent of `force_collect`- if we already
+ // have tokens, or can't even store them, then there's never a need to
+ // force collection of new tokens.
+ if !self.capture_cfg && matches!(ret.tokens_mut(), None | Some(Some(_))) {
+ return Ok(ret);
+ }
+
+ // This is very similar to the bail out check at the start of this function.
+ // Now that we've parsed an AST node, we have more information available.
+ if matches!(force_collect, ForceCollect::No)
+ // We now have inner attributes available, so this check is more precise
+ // than `attrs.maybe_needs_tokens()` at the start of the function.
+ // As a result, we don't need to check `R::SUPPORTS_CUSTOM_INNER_ATTRS`
+ && !crate::parser::attr::maybe_needs_tokens(ret.attrs())
+ // Subtle: We call `has_cfg_or_cfg_attr` with the attrs from `ret`.
+ // This ensures that we consider inner attributes (e.g. `#![cfg]`),
+ // which require us to have tokens available
+ // We also call `has_cfg_or_cfg_attr` at the beginning of this function,
+ // but we only bail out if there's no possibility of inner attributes
+ // (!R::SUPPORTS_CUSTOM_INNER_ATTRS)
+ // We only capture about `#[cfg]` or `#[cfg_attr]` in `capture_cfg`
+ // mode - during normal parsing, we don't need any special capturing
+ // for those attributes, since they're builtin.
+ && !(self.capture_cfg && has_cfg_or_cfg_attr(ret.attrs()))
+ {
+ return Ok(ret);
+ }
+
+ let mut inner_attr_replace_ranges = Vec::new();
+ // Take the captured ranges for any inner attributes that we parsed.
+ for inner_attr in ret.attrs().iter().filter(|a| a.style == ast::AttrStyle::Inner) {
+ if let Some(attr_range) = self.capture_state.inner_attr_ranges.remove(&inner_attr.id) {
+ inner_attr_replace_ranges.push(attr_range);
+ } else {
+ self.sess
+ .span_diagnostic
+ .delay_span_bug(inner_attr.span, "Missing token range for attribute");
+ }
+ }
+
+ let replace_ranges_end = self.capture_state.replace_ranges.len();
+
+ let cursor_snapshot_next_calls = cursor_snapshot.num_next_calls;
+ let mut end_pos = self.token_cursor.num_next_calls;
+
+ // Capture a trailing token if requested by the callback 'f'
+ match trailing {
+ TrailingToken::None => {}
+ TrailingToken::Semi => {
+ assert_eq!(self.token.kind, token::Semi);
+ end_pos += 1;
+ }
+ TrailingToken::MaybeComma => {
+ if self.token.kind == token::Comma {
+ end_pos += 1;
+ }
+ }
+ }
+
+ // If we 'broke' the last token (e.g. breaking a '>>' token to two '>' tokens),
+ // then extend the range of captured tokens to include it, since the parser
+ // was not actually bumped past it. When the `LazyTokenStream` gets converted
+ // into an `AttrAnnotatedTokenStream`, we will create the proper token.
+ if self.token_cursor.break_last_token {
+ assert_eq!(
+ trailing,
+ TrailingToken::None,
+ "Cannot set `break_last_token` and have trailing token"
+ );
+ end_pos += 1;
+ }
+
+ let num_calls = end_pos - cursor_snapshot_next_calls;
+
+ // If we have no attributes, then we will never need to
+ // use any replace ranges.
+ let replace_ranges: Box<[ReplaceRange]> = if ret.attrs().is_empty() && !self.capture_cfg {
+ Box::new([])
+ } else {
+ // Grab any replace ranges that occur *inside* the current AST node.
+ // We will perform the actual replacement when we convert the `LazyTokenStream`
+ // to an `AttrAnnotatedTokenStream`
+ let start_calls: u32 = cursor_snapshot_next_calls.try_into().unwrap();
+ self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end]
+ .iter()
+ .cloned()
+ .chain(inner_attr_replace_ranges.clone().into_iter())
+ .map(|(range, tokens)| {
+ ((range.start - start_calls)..(range.end - start_calls), tokens)
+ })
+ .collect()
+ };
+
+ let tokens = LazyTokenStream::new(LazyTokenStreamImpl {
+ start_token,
+ num_calls,
+ cursor_snapshot,
+ break_last_token: self.token_cursor.break_last_token,
+ replace_ranges,
+ });
+
+ // If we support tokens at all
+ if let Some(target_tokens) = ret.tokens_mut() {
+ if target_tokens.is_none() {
+ // Store se our newly captured tokens into the AST node
+ *target_tokens = Some(tokens.clone());
+ }
+ }
+
+ let final_attrs = ret.attrs();
+
+ // If `capture_cfg` is set and we're inside a recursive call to
+ // `collect_tokens_trailing_token`, then we need to register a replace range
+ // if we have `#[cfg]` or `#[cfg_attr]`. This allows us to run eager cfg-expansion
+ // on the captured token stream.
+ if self.capture_cfg
+ && matches!(self.capture_state.capturing, Capturing::Yes)
+ && has_cfg_or_cfg_attr(&final_attrs)
+ {
+ let attr_data = AttributesData { attrs: final_attrs.to_vec().into(), tokens };
+
+ // Replace the entire AST node that we just parsed, including attributes,
+ // with a `FlatToken::AttrTarget`. If this AST node is inside an item
+ // that has `#[derive]`, then this will allow us to cfg-expand this
+ // AST node.
+ let start_pos =
+ if has_outer_attrs { attrs.start_pos } else { cursor_snapshot_next_calls };
+ let new_tokens = vec![(FlatToken::AttrTarget(attr_data), Spacing::Alone)];
+
+ assert!(
+ !self.token_cursor.break_last_token,
+ "Should not have unglued last token with cfg attr"
+ );
+ let range: Range<u32> = (start_pos.try_into().unwrap())..(end_pos.try_into().unwrap());
+ self.capture_state.replace_ranges.push((range, new_tokens));
+ self.capture_state.replace_ranges.extend(inner_attr_replace_ranges);
+ }
+
+ // Only clear our `replace_ranges` when we're finished capturing entirely.
+ if matches!(self.capture_state.capturing, Capturing::No) {
+ self.capture_state.replace_ranges.clear();
+ // We don't clear `inner_attr_ranges`, as doing so repeatedly
+ // had a measurable performance impact. Most inner attributes that
+ // we insert will get removed - when we drop the parser, we'll free
+ // up the memory used by any attributes that we didn't remove from the map.
+ }
+ Ok(ret)
+ }
+}
+
+/// Converts a flattened iterator of tokens (including open and close delimiter tokens)
+/// into a `TokenStream`, creating a `TokenTree::Delimited` for each matching pair
+/// of open and close delims.
+fn make_token_stream(
+ mut iter: impl Iterator<Item = (FlatToken, Spacing)>,
+ break_last_token: bool,
+) -> AttrAnnotatedTokenStream {
+ #[derive(Debug)]
+ struct FrameData {
+ // This is `None` for the first frame, `Some` for all others.
+ open_delim_sp: Option<(Delimiter, Span)>,
+ inner: Vec<(AttrAnnotatedTokenTree, Spacing)>,
+ }
+ let mut stack = vec![FrameData { open_delim_sp: None, inner: vec![] }];
+ let mut token_and_spacing = iter.next();
+ while let Some((token, spacing)) = token_and_spacing {
+ match token {
+ FlatToken::Token(Token { kind: TokenKind::OpenDelim(delim), span }) => {
+ stack.push(FrameData { open_delim_sp: Some((delim, span)), inner: vec![] });
+ }
+ FlatToken::Token(Token { kind: TokenKind::CloseDelim(delim), span }) => {
+ let frame_data = stack
+ .pop()
+ .unwrap_or_else(|| panic!("Token stack was empty for token: {:?}", token));
+
+ let (open_delim, open_sp) = frame_data.open_delim_sp.unwrap();
+ assert_eq!(
+ open_delim, delim,
+ "Mismatched open/close delims: open={:?} close={:?}",
+ open_delim, span
+ );
+ let dspan = DelimSpan::from_pair(open_sp, span);
+ let stream = AttrAnnotatedTokenStream::new(frame_data.inner);
+ let delimited = AttrAnnotatedTokenTree::Delimited(dspan, delim, stream);
+ stack
+ .last_mut()
+ .unwrap_or_else(|| {
+ panic!("Bottom token frame is missing for token: {:?}", token)
+ })
+ .inner
+ .push((delimited, Spacing::Alone));
+ }
+ FlatToken::Token(token) => stack
+ .last_mut()
+ .expect("Bottom token frame is missing!")
+ .inner
+ .push((AttrAnnotatedTokenTree::Token(token), spacing)),
+ FlatToken::AttrTarget(data) => stack
+ .last_mut()
+ .expect("Bottom token frame is missing!")
+ .inner
+ .push((AttrAnnotatedTokenTree::Attributes(data), spacing)),
+ FlatToken::Empty => {}
+ }
+ token_and_spacing = iter.next();
+ }
+ let mut final_buf = stack.pop().expect("Missing final buf!");
+ if break_last_token {
+ let (last_token, spacing) = final_buf.inner.pop().unwrap();
+ if let AttrAnnotatedTokenTree::Token(last_token) = last_token {
+ let unglued_first = last_token.kind.break_two_token_op().unwrap().0;
+
+ // An 'unglued' token is always two ASCII characters
+ let mut first_span = last_token.span.shrink_to_lo();
+ first_span = first_span.with_hi(first_span.lo() + rustc_span::BytePos(1));
+
+ final_buf.inner.push((
+ AttrAnnotatedTokenTree::Token(Token::new(unglued_first, first_span)),
+ spacing,
+ ));
+ } else {
+ panic!("Unexpected last token {:?}", last_token)
+ }
+ }
+ assert!(stack.is_empty(), "Stack should be empty: final_buf={:?} stack={:?}", final_buf, stack);
+ AttrAnnotatedTokenStream::new(final_buf.inner)
+}
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
new file mode 100644
index 000000000..a2155ac1d
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -0,0 +1,2740 @@
+use super::pat::Expected;
+use super::{
+ BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep,
+ TokenExpectType, TokenType,
+};
+
+use crate::lexer::UnmatchedBrace;
+use rustc_ast as ast;
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
+use rustc_ast::util::parser::AssocOp;
+use rustc_ast::{
+ AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
+ BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Mutability, Param, Pat,
+ PatKind, Path, PathSegment, QSelf, Ty, TyKind,
+};
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{
+ fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
+};
+use rustc_errors::{pluralize, struct_span_err, Diagnostic, EmissionGuarantee, ErrorGuaranteed};
+use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
+use rustc_span::source_map::Spanned;
+use rustc_span::symbol::{kw, Ident};
+use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
+use std::ops::{Deref, DerefMut};
+
+use std::mem::take;
+
+use crate::parser;
+use tracing::{debug, trace};
+
+const TURBOFISH_SUGGESTION_STR: &str =
+ "use `::<...>` instead of `<...>` to specify lifetime, type, or const arguments";
+
+/// Creates a placeholder argument.
+pub(super) fn dummy_arg(ident: Ident) -> Param {
+ let pat = P(Pat {
+ id: ast::DUMMY_NODE_ID,
+ kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
+ span: ident.span,
+ tokens: None,
+ });
+ let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
+ Param {
+ attrs: AttrVec::default(),
+ id: ast::DUMMY_NODE_ID,
+ pat,
+ span: ident.span,
+ ty: P(ty),
+ is_placeholder: false,
+ }
+}
+
+pub enum Error {
+ UselessDocComment,
+}
+
+impl Error {
+ fn span_err(
+ self,
+ sp: impl Into<MultiSpan>,
+ handler: &Handler,
+ ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+ match self {
+ Error::UselessDocComment => {
+ let mut err = struct_span_err!(
+ handler,
+ sp,
+ E0585,
+ "found a documentation comment that doesn't document anything",
+ );
+ err.help(
+ "doc comments must come before what they document, maybe a comment was \
+ intended with `//`?",
+ );
+ err
+ }
+ }
+ }
+}
+
+pub(super) trait RecoverQPath: Sized + 'static {
+ const PATH_STYLE: PathStyle = PathStyle::Expr;
+ fn to_ty(&self) -> Option<P<Ty>>;
+ fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
+}
+
+impl RecoverQPath for Ty {
+ const PATH_STYLE: PathStyle = PathStyle::Type;
+ fn to_ty(&self) -> Option<P<Ty>> {
+ Some(P(self.clone()))
+ }
+ fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+ Self {
+ span: path.span,
+ kind: TyKind::Path(qself, path),
+ id: ast::DUMMY_NODE_ID,
+ tokens: None,
+ }
+ }
+}
+
+impl RecoverQPath for Pat {
+ fn to_ty(&self) -> Option<P<Ty>> {
+ self.to_ty()
+ }
+ fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+ Self {
+ span: path.span,
+ kind: PatKind::Path(qself, path),
+ id: ast::DUMMY_NODE_ID,
+ tokens: None,
+ }
+ }
+}
+
+impl RecoverQPath for Expr {
+ fn to_ty(&self) -> Option<P<Ty>> {
+ self.to_ty()
+ }
+ fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+ Self {
+ span: path.span,
+ kind: ExprKind::Path(qself, path),
+ attrs: AttrVec::new(),
+ id: ast::DUMMY_NODE_ID,
+ tokens: None,
+ }
+ }
+}
+
+/// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
+pub(crate) enum ConsumeClosingDelim {
+ Yes,
+ No,
+}
+
+#[derive(Clone, Copy)]
+pub enum AttemptLocalParseRecovery {
+ Yes,
+ No,
+}
+
+impl AttemptLocalParseRecovery {
+ pub fn yes(&self) -> bool {
+ match self {
+ AttemptLocalParseRecovery::Yes => true,
+ AttemptLocalParseRecovery::No => false,
+ }
+ }
+
+ pub fn no(&self) -> bool {
+ match self {
+ AttemptLocalParseRecovery::Yes => false,
+ AttemptLocalParseRecovery::No => true,
+ }
+ }
+}
+
+/// Information for emitting suggestions and recovering from
+/// C-style `i++`, `--i`, etc.
+#[derive(Debug, Copy, Clone)]
+struct IncDecRecovery {
+ /// Is this increment/decrement its own statement?
+ standalone: IsStandalone,
+ /// Is this an increment or decrement?
+ op: IncOrDec,
+ /// Is this pre- or postfix?
+ fixity: UnaryFixity,
+}
+
+/// Is an increment or decrement expression its own statement?
+#[derive(Debug, Copy, Clone)]
+enum IsStandalone {
+ /// It's standalone, i.e., its own statement.
+ Standalone,
+ /// It's a subexpression, i.e., *not* standalone.
+ Subexpr,
+ /// It's maybe standalone; we're not sure.
+ Maybe,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+enum IncOrDec {
+ Inc,
+ // FIXME: `i--` recovery isn't implemented yet
+ #[allow(dead_code)]
+ Dec,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+enum UnaryFixity {
+ Pre,
+ Post,
+}
+
+impl IncOrDec {
+ fn chr(&self) -> char {
+ match self {
+ Self::Inc => '+',
+ Self::Dec => '-',
+ }
+ }
+
+ fn name(&self) -> &'static str {
+ match self {
+ Self::Inc => "increment",
+ Self::Dec => "decrement",
+ }
+ }
+}
+
+impl std::fmt::Display for UnaryFixity {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ match self {
+ Self::Pre => write!(f, "prefix"),
+ Self::Post => write!(f, "postfix"),
+ }
+ }
+}
+
+struct MultiSugg {
+ msg: String,
+ patches: Vec<(Span, String)>,
+ applicability: Applicability,
+}
+
+impl MultiSugg {
+ fn emit<G: EmissionGuarantee>(self, err: &mut DiagnosticBuilder<'_, G>) {
+ err.multipart_suggestion(&self.msg, self.patches, self.applicability);
+ }
+
+ /// Overrides individual messages and applicabilities.
+ fn emit_many<G: EmissionGuarantee>(
+ err: &mut DiagnosticBuilder<'_, G>,
+ msg: &str,
+ applicability: Applicability,
+ suggestions: impl Iterator<Item = Self>,
+ ) {
+ err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
+ }
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::maybe_report_ambiguous_plus)]
+struct AmbiguousPlus {
+ pub sum_ty: String,
+ #[primary_span]
+ #[suggestion(code = "({sum_ty})")]
+ pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::maybe_recover_from_bad_type_plus, code = "E0178")]
+struct BadTypePlus {
+ pub ty: String,
+ #[primary_span]
+ pub span: Span,
+ #[subdiagnostic]
+ pub sub: BadTypePlusSub,
+}
+
+#[derive(SessionSubdiagnostic)]
+pub enum BadTypePlusSub {
+ #[suggestion(
+ parser::add_paren,
+ code = "{sum_with_parens}",
+ applicability = "machine-applicable"
+ )]
+ AddParen {
+ sum_with_parens: String,
+ #[primary_span]
+ span: Span,
+ },
+ #[label(parser::forgot_paren)]
+ ForgotParen {
+ #[primary_span]
+ span: Span,
+ },
+ #[label(parser::expect_path)]
+ ExpectPath {
+ #[primary_span]
+ span: Span,
+ },
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::maybe_recover_from_bad_qpath_stage_2)]
+struct BadQPathStage2 {
+ #[primary_span]
+ #[suggestion(applicability = "maybe-incorrect")]
+ span: Span,
+ ty: String,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::incorrect_semicolon)]
+struct IncorrectSemicolon<'a> {
+ #[primary_span]
+ #[suggestion_short(applicability = "machine-applicable")]
+ span: Span,
+ #[help]
+ opt_help: Option<()>,
+ name: &'a str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::incorrect_use_of_await)]
+struct IncorrectUseOfAwait {
+ #[primary_span]
+ #[suggestion(parser::parentheses_suggestion, applicability = "machine-applicable")]
+ span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::incorrect_use_of_await)]
+struct IncorrectAwait {
+ #[primary_span]
+ span: Span,
+ #[suggestion(parser::postfix_suggestion, code = "{expr}.await{question_mark}")]
+ sugg_span: (Span, Applicability),
+ expr: String,
+ question_mark: &'static str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(parser::in_in_typo)]
+struct InInTypo {
+ #[primary_span]
+ span: Span,
+ #[suggestion(applicability = "machine-applicable")]
+ sugg_span: Span,
+}
+
+// SnapshotParser is used to create a snapshot of the parser
+// without causing duplicate errors being emitted when the `Parser`
+// is dropped.
+pub struct SnapshotParser<'a> {
+ parser: Parser<'a>,
+ unclosed_delims: Vec<UnmatchedBrace>,
+}
+
+impl<'a> Deref for SnapshotParser<'a> {
+ type Target = Parser<'a>;
+
+ fn deref(&self) -> &Self::Target {
+ &self.parser
+ }
+}
+
+impl<'a> DerefMut for SnapshotParser<'a> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.parser
+ }
+}
+
+impl<'a> Parser<'a> {
+ #[rustc_lint_diagnostics]
+ pub(super) fn span_err<S: Into<MultiSpan>>(
+ &self,
+ sp: S,
+ err: Error,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ err.span_err(sp, self.diagnostic())
+ }
+
+ #[rustc_lint_diagnostics]
+ pub fn struct_span_err<S: Into<MultiSpan>>(
+ &self,
+ sp: S,
+ m: impl Into<DiagnosticMessage>,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ self.sess.span_diagnostic.struct_span_err(sp, m)
+ }
+
+ pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: impl Into<DiagnosticMessage>) -> ! {
+ self.sess.span_diagnostic.span_bug(sp, m)
+ }
+
+ pub(super) fn diagnostic(&self) -> &'a Handler {
+ &self.sess.span_diagnostic
+ }
+
+ /// Replace `self` with `snapshot.parser` and extend `unclosed_delims` with `snapshot.unclosed_delims`.
+ /// This is to avoid losing unclosed delims errors `create_snapshot_for_diagnostic` clears.
+ pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
+ *self = snapshot.parser;
+ self.unclosed_delims.extend(snapshot.unclosed_delims.clone());
+ }
+
+ pub fn unclosed_delims(&self) -> &[UnmatchedBrace] {
+ &self.unclosed_delims
+ }
+
+ /// Create a snapshot of the `Parser`.
+ pub fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
+ let mut snapshot = self.clone();
+ let unclosed_delims = self.unclosed_delims.clone();
+ // Clear `unclosed_delims` in snapshot to avoid
+ // duplicate errors being emitted when the `Parser`
+ // is dropped (which may or may not happen, depending
+ // if the parsing the snapshot is created for is successful)
+ snapshot.unclosed_delims.clear();
+ SnapshotParser { parser: snapshot, unclosed_delims }
+ }
+
+ pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
+ self.sess.source_map().span_to_snippet(span)
+ }
+
+ pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let mut err = self.struct_span_err(
+ self.token.span,
+ &format!("expected identifier, found {}", super::token_descr(&self.token)),
+ );
+ let valid_follow = &[
+ TokenKind::Eq,
+ TokenKind::Colon,
+ TokenKind::Comma,
+ TokenKind::Semi,
+ TokenKind::ModSep,
+ TokenKind::OpenDelim(Delimiter::Brace),
+ TokenKind::OpenDelim(Delimiter::Parenthesis),
+ TokenKind::CloseDelim(Delimiter::Brace),
+ TokenKind::CloseDelim(Delimiter::Parenthesis),
+ ];
+ match self.token.ident() {
+ Some((ident, false))
+ if ident.is_raw_guess()
+ && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
+ {
+ err.span_suggestion_verbose(
+ ident.span.shrink_to_lo(),
+ &format!("escape `{}` to use it as an identifier", ident.name),
+ "r#",
+ Applicability::MaybeIncorrect,
+ );
+ }
+ _ => {}
+ }
+ if let Some(token_descr) = super::token_descr_opt(&self.token) {
+ err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
+ } else {
+ err.span_label(self.token.span, "expected identifier");
+ if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
+ err.span_suggestion(
+ self.token.span,
+ "remove this comma",
+ "",
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ err
+ }
+
+ pub(super) fn expected_one_of_not_found(
+ &mut self,
+ edible: &[TokenKind],
+ inedible: &[TokenKind],
+ ) -> PResult<'a, bool /* recovered */> {
+ debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
+ fn tokens_to_string(tokens: &[TokenType]) -> String {
+ let mut i = tokens.iter();
+ // This might be a sign we need a connect method on `Iterator`.
+ let b = i.next().map_or_else(String::new, |t| t.to_string());
+ i.enumerate().fold(b, |mut b, (i, a)| {
+ if tokens.len() > 2 && i == tokens.len() - 2 {
+ b.push_str(", or ");
+ } else if tokens.len() == 2 && i == tokens.len() - 2 {
+ b.push_str(" or ");
+ } else {
+ b.push_str(", ");
+ }
+ b.push_str(&a.to_string());
+ b
+ })
+ }
+
+ let mut expected = edible
+ .iter()
+ .map(|x| TokenType::Token(x.clone()))
+ .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
+ .chain(self.expected_tokens.iter().cloned())
+ .filter_map(|token| {
+ // filter out suggestions which suggest the same token which was found and deemed incorrect
+ fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
+ if let TokenKind::Ident(current_sym, _) = found {
+ if let TokenType::Keyword(suggested_sym) = expected {
+ return current_sym == suggested_sym;
+ }
+ }
+ false
+ }
+ if token != parser::TokenType::Token(self.token.kind.clone()) {
+ let eq = is_ident_eq_keyword(&self.token.kind, &token);
+ // if the suggestion is a keyword and the found token is an ident,
+ // the content of which are equal to the suggestion's content,
+ // we can remove that suggestion (see the return None statement below)
+
+ // if this isn't the case however, and the suggestion is a token the
+ // content of which is the same as the found token's, we remove it as well
+ if !eq {
+ if let TokenType::Token(kind) = &token {
+ if kind == &self.token.kind {
+ return None;
+ }
+ }
+ return Some(token);
+ }
+ }
+ return None;
+ })
+ .collect::<Vec<_>>();
+ expected.sort_by_cached_key(|x| x.to_string());
+ expected.dedup();
+
+ let sm = self.sess.source_map();
+ let msg = format!("expected `;`, found {}", super::token_descr(&self.token));
+ let appl = Applicability::MachineApplicable;
+ if expected.contains(&TokenType::Token(token::Semi)) {
+ if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
+ // Likely inside a macro, can't provide meaningful suggestions.
+ } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
+ // The current token is in the same line as the prior token, not recoverable.
+ } else if [token::Comma, token::Colon].contains(&self.token.kind)
+ && self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis)
+ {
+ // Likely typo: The current token is on a new line and is expected to be
+ // `.`, `;`, `?`, or an operator after a close delimiter token.
+ //
+ // let a = std::process::Command::new("echo")
+ // .arg("1")
+ // ,arg("2")
+ // ^
+ // https://github.com/rust-lang/rust/issues/72253
+ } else if self.look_ahead(1, |t| {
+ t == &token::CloseDelim(Delimiter::Brace)
+ || t.can_begin_expr() && t.kind != token::Colon
+ }) && [token::Comma, token::Colon].contains(&self.token.kind)
+ {
+ // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
+ // either `,` or `:`, and the next token could either start a new statement or is a
+ // block close. For example:
+ //
+ // let x = 32:
+ // let y = 42;
+ self.bump();
+ let sp = self.prev_token.span;
+ self.struct_span_err(sp, &msg)
+ .span_suggestion_short(sp, "change this to `;`", ";", appl)
+ .emit();
+ return Ok(true);
+ } else if self.look_ahead(0, |t| {
+ t == &token::CloseDelim(Delimiter::Brace)
+ || (t.can_begin_expr() && t != &token::Semi && t != &token::Pound)
+ // Avoid triggering with too many trailing `#` in raw string.
+ || (sm.is_multiline(
+ self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo())
+ ) && t == &token::Pound)
+ }) && !expected.contains(&TokenType::Token(token::Comma))
+ {
+ // Missing semicolon typo. This is triggered if the next token could either start a
+ // new statement or is a block close. For example:
+ //
+ // let x = 32
+ // let y = 42;
+ let sp = self.prev_token.span.shrink_to_hi();
+ self.struct_span_err(sp, &msg)
+ .span_label(self.token.span, "unexpected token")
+ .span_suggestion_short(sp, "add `;` here", ";", appl)
+ .emit();
+ return Ok(true);
+ }
+ }
+
+ let expect = tokens_to_string(&expected);
+ let actual = super::token_descr(&self.token);
+ let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
+ let short_expect = if expected.len() > 6 {
+ format!("{} possible tokens", expected.len())
+ } else {
+ expect.clone()
+ };
+ (
+ format!("expected one of {expect}, found {actual}"),
+ (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")),
+ )
+ } else if expected.is_empty() {
+ (
+ format!("unexpected token: {}", actual),
+ (self.prev_token.span, "unexpected token after this".to_string()),
+ )
+ } else {
+ (
+ format!("expected {expect}, found {actual}"),
+ (self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
+ )
+ };
+ self.last_unexpected_token_span = Some(self.token.span);
+ let mut err = self.struct_span_err(self.token.span, &msg_exp);
+
+ if let TokenKind::Ident(symbol, _) = &self.prev_token.kind {
+ if symbol.as_str() == "public" {
+ err.span_suggestion_short(
+ self.prev_token.span,
+ "write `pub` instead of `public` to make the item public",
+ "pub",
+ appl,
+ );
+ }
+ }
+
+ // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
+ // there are unclosed angle brackets
+ if self.unmatched_angle_bracket_count > 0
+ && self.token.kind == TokenKind::Eq
+ && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
+ {
+ err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
+ }
+
+ let sp = if self.token == token::Eof {
+ // This is EOF; don't want to point at the following char, but rather the last token.
+ self.prev_token.span
+ } else {
+ label_sp
+ };
+ match self.recover_closing_delimiter(
+ &expected
+ .iter()
+ .filter_map(|tt| match tt {
+ TokenType::Token(t) => Some(t.clone()),
+ _ => None,
+ })
+ .collect::<Vec<_>>(),
+ err,
+ ) {
+ Err(e) => err = e,
+ Ok(recovered) => {
+ return Ok(recovered);
+ }
+ }
+
+ if self.check_too_many_raw_str_terminators(&mut err) {
+ if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
+ err.emit();
+ return Ok(true);
+ } else {
+ return Err(err);
+ }
+ }
+
+ if self.prev_token.span == DUMMY_SP {
+ // Account for macro context where the previous span might not be
+ // available to avoid incorrect output (#54841).
+ err.span_label(self.token.span, label_exp);
+ } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
+ // When the spans are in the same line, it means that the only content between
+ // them is whitespace, point at the found token in that case:
+ //
+ // X | () => { syntax error };
+ // | ^^^^^ expected one of 8 possible tokens here
+ //
+ // instead of having:
+ //
+ // X | () => { syntax error };
+ // | -^^^^^ unexpected token
+ // | |
+ // | expected one of 8 possible tokens here
+ err.span_label(self.token.span, label_exp);
+ } else {
+ err.span_label(sp, label_exp);
+ err.span_label(self.token.span, "unexpected token");
+ }
+ self.maybe_annotate_with_ascription(&mut err, false);
+ Err(err)
+ }
+
+ fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
+ let sm = self.sess.source_map();
+ match (&self.prev_token.kind, &self.token.kind) {
+ (
+ TokenKind::Literal(Lit {
+ kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
+ ..
+ }),
+ TokenKind::Pound,
+ ) if !sm.is_multiline(
+ self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
+ ) =>
+ {
+ let n_hashes: u8 = *n_hashes;
+ err.set_primary_message("too many `#` when terminating raw string");
+ let str_span = self.prev_token.span;
+ let mut span = self.token.span;
+ let mut count = 0;
+ while self.token.kind == TokenKind::Pound
+ && !sm.is_multiline(span.shrink_to_hi().until(self.token.span.shrink_to_lo()))
+ {
+ span = span.with_hi(self.token.span.hi());
+ self.bump();
+ count += 1;
+ }
+ err.set_span(span);
+ err.span_suggestion(
+ span,
+ &format!("remove the extra `#`{}", pluralize!(count)),
+ "",
+ Applicability::MachineApplicable,
+ );
+ err.span_label(
+ str_span,
+ &format!("this raw string started with {n_hashes} `#`{}", pluralize!(n_hashes)),
+ );
+ true
+ }
+ _ => false,
+ }
+ }
+
+ pub fn maybe_suggest_struct_literal(
+ &mut self,
+ lo: Span,
+ s: BlockCheckMode,
+ ) -> Option<PResult<'a, P<Block>>> {
+ if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
+ // We might be having a struct literal where people forgot to include the path:
+ // fn foo() -> Foo {
+ // field: value,
+ // }
+ let mut snapshot = self.create_snapshot_for_diagnostic();
+ let path =
+ Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
+ let struct_expr = snapshot.parse_struct_expr(None, path, AttrVec::new(), false);
+ let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
+ return Some(match (struct_expr, block_tail) {
+ (Ok(expr), Err(mut err)) => {
+ // We have encountered the following:
+ // fn foo() -> Foo {
+ // field: value,
+ // }
+ // Suggest:
+ // fn foo() -> Foo { Path {
+ // field: value,
+ // } }
+ err.delay_as_bug();
+ self.struct_span_err(
+ expr.span,
+ fluent::parser::struct_literal_body_without_path,
+ )
+ .multipart_suggestion(
+ fluent::parser::suggestion,
+ vec![
+ (expr.span.shrink_to_lo(), "{ SomeStruct ".to_string()),
+ (expr.span.shrink_to_hi(), " }".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ self.restore_snapshot(snapshot);
+ let mut tail = self.mk_block(
+ vec![self.mk_stmt_err(expr.span)],
+ s,
+ lo.to(self.prev_token.span),
+ );
+ tail.could_be_bare_literal = true;
+ Ok(tail)
+ }
+ (Err(err), Ok(tail)) => {
+ // We have a block tail that contains a somehow valid type ascription expr.
+ err.cancel();
+ Ok(tail)
+ }
+ (Err(snapshot_err), Err(err)) => {
+ // We don't know what went wrong, emit the normal error.
+ snapshot_err.cancel();
+ self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+ Err(err)
+ }
+ (Ok(_), Ok(mut tail)) => {
+ tail.could_be_bare_literal = true;
+ Ok(tail)
+ }
+ });
+ }
+ None
+ }
+
+ pub fn maybe_annotate_with_ascription(
+ &mut self,
+ err: &mut Diagnostic,
+ maybe_expected_semicolon: bool,
+ ) {
+ if let Some((sp, likely_path)) = self.last_type_ascription.take() {
+ let sm = self.sess.source_map();
+ let next_pos = sm.lookup_char_pos(self.token.span.lo());
+ let op_pos = sm.lookup_char_pos(sp.hi());
+
+ let allow_unstable = self.sess.unstable_features.is_nightly_build();
+
+ if likely_path {
+ err.span_suggestion(
+ sp,
+ "maybe write a path separator here",
+ "::",
+ if allow_unstable {
+ Applicability::MaybeIncorrect
+ } else {
+ Applicability::MachineApplicable
+ },
+ );
+ self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
+ } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
+ err.span_suggestion(
+ sp,
+ "try using a semicolon",
+ ";",
+ Applicability::MaybeIncorrect,
+ );
+ } else if allow_unstable {
+ err.span_label(sp, "tried to parse a type due to this type ascription");
+ } else {
+ err.span_label(sp, "tried to parse a type due to this");
+ }
+ if allow_unstable {
+ // Give extra information about type ascription only if it's a nightly compiler.
+ err.note(
+ "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
+ `<expr>: <type>`",
+ );
+ if !likely_path {
+ // Avoid giving too much info when it was likely an unrelated typo.
+ err.note(
+ "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
+ for more information",
+ );
+ }
+ }
+ }
+ }
+
+ /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
+ /// passes through any errors encountered. Used for error recovery.
+ pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
+ if let Err(err) =
+ self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
+ Ok(p.parse_token_tree())
+ })
+ {
+ err.cancel();
+ }
+ }
+
+ /// This function checks if there are trailing angle brackets and produces
+ /// a diagnostic to suggest removing them.
+ ///
+ /// ```ignore (diagnostic)
+ /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
+ /// ^^ help: remove extra angle brackets
+ /// ```
+ ///
+ /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
+ /// up until one of the tokens in 'end' was encountered, and an error was emitted.
+ pub(super) fn check_trailing_angle_brackets(
+ &mut self,
+ segment: &PathSegment,
+ end: &[&TokenKind],
+ ) -> bool {
+ // This function is intended to be invoked after parsing a path segment where there are two
+ // cases:
+ //
+ // 1. A specific token is expected after the path segment.
+ // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
+ // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
+ // 2. No specific token is expected after the path segment.
+ // eg. `x.foo` (field access)
+ //
+ // This function is called after parsing `.foo` and before parsing the token `end` (if
+ // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
+ // `Foo::<Bar>`.
+
+ // We only care about trailing angle brackets if we previously parsed angle bracket
+ // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
+ // removed in this case:
+ //
+ // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
+ //
+ // This case is particularly tricky as we won't notice it just looking at the tokens -
+ // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
+ // have already been parsed):
+ //
+ // `x.foo::<u32>>>(3)`
+ let parsed_angle_bracket_args =
+ segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
+
+ debug!(
+ "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
+ parsed_angle_bracket_args,
+ );
+ if !parsed_angle_bracket_args {
+ return false;
+ }
+
+ // Keep the span at the start so we can highlight the sequence of `>` characters to be
+ // removed.
+ let lo = self.token.span;
+
+ // We need to look-ahead to see if we have `>` characters without moving the cursor forward
+ // (since we might have the field access case and the characters we're eating are
+ // actual operators and not trailing characters - ie `x.foo >> 3`).
+ let mut position = 0;
+
+ // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
+ // many of each (so we can correctly pluralize our error messages) and continue to
+ // advance.
+ let mut number_of_shr = 0;
+ let mut number_of_gt = 0;
+ while self.look_ahead(position, |t| {
+ trace!("check_trailing_angle_brackets: t={:?}", t);
+ if *t == token::BinOp(token::BinOpToken::Shr) {
+ number_of_shr += 1;
+ true
+ } else if *t == token::Gt {
+ number_of_gt += 1;
+ true
+ } else {
+ false
+ }
+ }) {
+ position += 1;
+ }
+
+ // If we didn't find any trailing `>` characters, then we have nothing to error about.
+ debug!(
+ "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
+ number_of_gt, number_of_shr,
+ );
+ if number_of_gt < 1 && number_of_shr < 1 {
+ return false;
+ }
+
+ // Finally, double check that we have our end token as otherwise this is the
+ // second case.
+ if self.look_ahead(position, |t| {
+ trace!("check_trailing_angle_brackets: t={:?}", t);
+ end.contains(&&t.kind)
+ }) {
+ // Eat from where we started until the end token so that parsing can continue
+ // as if we didn't have those extra angle brackets.
+ self.eat_to_tokens(end);
+ let span = lo.until(self.token.span);
+
+ let total_num_of_gt = number_of_gt + number_of_shr * 2;
+ self.struct_span_err(
+ span,
+ &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
+ )
+ .span_suggestion(
+ span,
+ &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ return true;
+ }
+ false
+ }
+
+ /// Check if a method call with an intended turbofish has been written without surrounding
+ /// angle brackets.
+ pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
+ if token::ModSep == self.token.kind && segment.args.is_none() {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ self.bump();
+ let lo = self.token.span;
+ match self.parse_angle_args(None) {
+ Ok(args) => {
+ let span = lo.to(self.prev_token.span);
+ // Detect trailing `>` like in `x.collect::Vec<_>>()`.
+ let mut trailing_span = self.prev_token.span.shrink_to_hi();
+ while self.token.kind == token::BinOp(token::Shr)
+ || self.token.kind == token::Gt
+ {
+ trailing_span = trailing_span.to(self.token.span);
+ self.bump();
+ }
+ if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
+ // Recover from bad turbofish: `foo.collect::Vec<_>()`.
+ let args = AngleBracketedArgs { args, span }.into();
+ segment.args = args;
+
+ self.struct_span_err(
+ span,
+ "generic parameters without surrounding angle brackets",
+ )
+ .multipart_suggestion(
+ "surround the type parameters with angle brackets",
+ vec![
+ (span.shrink_to_lo(), "<".to_string()),
+ (trailing_span, ">".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ } else {
+ // This doesn't look like an invalid turbofish, can't recover parse state.
+ self.restore_snapshot(snapshot);
+ }
+ }
+ Err(err) => {
+ // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
+ // generic parse error instead.
+ err.cancel();
+ self.restore_snapshot(snapshot);
+ }
+ }
+ }
+ }
+
+ /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
+ /// encounter a parse error when encountering the first `,`.
+ pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
+ &mut self,
+ mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
+ expr: &mut P<Expr>,
+ ) -> PResult<'a, ()> {
+ if let ExprKind::Binary(binop, _, _) = &expr.kind
+ && let ast::BinOpKind::Lt = binop.node
+ && self.eat(&token::Comma)
+ {
+ let x = self.parse_seq_to_before_end(
+ &token::Gt,
+ SeqSep::trailing_allowed(token::Comma),
+ |p| p.parse_generic_arg(None),
+ );
+ match x {
+ Ok((_, _, false)) => {
+ if self.eat(&token::Gt) {
+ e.span_suggestion_verbose(
+ binop.span.shrink_to_lo(),
+ TURBOFISH_SUGGESTION_STR,
+ "::",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ match self.parse_expr() {
+ Ok(_) => {
+ *expr =
+ self.mk_expr_err(expr.span.to(self.prev_token.span));
+ return Ok(());
+ }
+ Err(err) => {
+ *expr = self.mk_expr_err(expr.span);
+ err.cancel();
+ }
+ }
+ }
+ }
+ Err(err) => {
+ err.cancel();
+ }
+ _ => {}
+ }
+ }
+ Err(e)
+ }
+
+ /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
+ /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
+ /// parenthesising the leftmost comparison.
+ fn attempt_chained_comparison_suggestion(
+ &mut self,
+ err: &mut Diagnostic,
+ inner_op: &Expr,
+ outer_op: &Spanned<AssocOp>,
+ ) -> bool /* advanced the cursor */ {
+ if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
+ if let ExprKind::Field(_, ident) = l1.kind
+ && ident.as_str().parse::<i32>().is_err()
+ && !matches!(r1.kind, ExprKind::Lit(_))
+ {
+ // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
+ // suggestion being the only one to apply is high.
+ return false;
+ }
+ let mut enclose = |left: Span, right: Span| {
+ err.multipart_suggestion(
+ "parenthesize the comparison",
+ vec![
+ (left.shrink_to_lo(), "(".to_string()),
+ (right.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ };
+ return match (op.node, &outer_op.node) {
+ // `x == y == z`
+ (BinOpKind::Eq, AssocOp::Equal) |
+ // `x < y < z` and friends.
+ (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
+ (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
+ // `x > y > z` and friends.
+ (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
+ (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
+ let expr_to_str = |e: &Expr| {
+ self.span_to_snippet(e.span)
+ .unwrap_or_else(|_| pprust::expr_to_string(&e))
+ };
+ err.span_suggestion_verbose(
+ inner_op.span.shrink_to_hi(),
+ "split the comparison into two",
+ format!(" && {}", expr_to_str(&r1)),
+ Applicability::MaybeIncorrect,
+ );
+ false // Keep the current parse behavior, where the AST is `(x < y) < z`.
+ }
+ // `x == y < z`
+ (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
+ // Consume `z`/outer-op-rhs.
+ let snapshot = self.create_snapshot_for_diagnostic();
+ match self.parse_expr() {
+ Ok(r2) => {
+ // We are sure that outer-op-rhs could be consumed, the suggestion is
+ // likely correct.
+ enclose(r1.span, r2.span);
+ true
+ }
+ Err(expr_err) => {
+ expr_err.cancel();
+ self.restore_snapshot(snapshot);
+ false
+ }
+ }
+ }
+ // `x > y == z`
+ (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ // At this point it is always valid to enclose the lhs in parentheses, no
+ // further checks are necessary.
+ match self.parse_expr() {
+ Ok(_) => {
+ enclose(l1.span, r1.span);
+ true
+ }
+ Err(expr_err) => {
+ expr_err.cancel();
+ self.restore_snapshot(snapshot);
+ false
+ }
+ }
+ }
+ _ => false,
+ };
+ }
+ false
+ }
+
+ /// Produces an error if comparison operators are chained (RFC #558).
+ /// We only need to check the LHS, not the RHS, because all comparison ops have same
+ /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
+ ///
+ /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
+ /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
+ /// case.
+ ///
+ /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
+ /// associative we can infer that we have:
+ ///
+ /// ```text
+ /// outer_op
+ /// / \
+ /// inner_op r2
+ /// / \
+ /// l1 r1
+ /// ```
+ pub(super) fn check_no_chained_comparison(
+ &mut self,
+ inner_op: &Expr,
+ outer_op: &Spanned<AssocOp>,
+ ) -> PResult<'a, Option<P<Expr>>> {
+ debug_assert!(
+ outer_op.node.is_comparison(),
+ "check_no_chained_comparison: {:?} is not comparison",
+ outer_op.node,
+ );
+
+ let mk_err_expr =
+ |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
+
+ match inner_op.kind {
+ ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
+ let mut err = self.struct_span_err(
+ vec![op.span, self.prev_token.span],
+ "comparison operators cannot be chained",
+ );
+
+ let suggest = |err: &mut Diagnostic| {
+ err.span_suggestion_verbose(
+ op.span.shrink_to_lo(),
+ TURBOFISH_SUGGESTION_STR,
+ "::",
+ Applicability::MaybeIncorrect,
+ );
+ };
+
+ // Include `<` to provide this recommendation even in a case like
+ // `Foo<Bar<Baz<Qux, ()>>>`
+ if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
+ || outer_op.node == AssocOp::Greater
+ {
+ if outer_op.node == AssocOp::Less {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ self.bump();
+ // So far we have parsed `foo<bar<`, consume the rest of the type args.
+ let modifiers =
+ [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
+ self.consume_tts(1, &modifiers);
+
+ if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
+ .contains(&self.token.kind)
+ {
+ // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
+ // parser and bail out.
+ self.restore_snapshot(snapshot);
+ }
+ }
+ return if token::ModSep == self.token.kind {
+ // We have some certainty that this was a bad turbofish at this point.
+ // `foo< bar >::`
+ suggest(&mut err);
+
+ let snapshot = self.create_snapshot_for_diagnostic();
+ self.bump(); // `::`
+
+ // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
+ match self.parse_expr() {
+ Ok(_) => {
+ // 99% certain that the suggestion is correct, continue parsing.
+ err.emit();
+ // FIXME: actually check that the two expressions in the binop are
+ // paths and resynthesize new fn call expression instead of using
+ // `ExprKind::Err` placeholder.
+ mk_err_expr(self, inner_op.span.to(self.prev_token.span))
+ }
+ Err(expr_err) => {
+ expr_err.cancel();
+ // Not entirely sure now, but we bubble the error up with the
+ // suggestion.
+ self.restore_snapshot(snapshot);
+ Err(err)
+ }
+ }
+ } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
+ // We have high certainty that this was a bad turbofish at this point.
+ // `foo< bar >(`
+ suggest(&mut err);
+ // Consume the fn call arguments.
+ match self.consume_fn_args() {
+ Err(()) => Err(err),
+ Ok(()) => {
+ err.emit();
+ // FIXME: actually check that the two expressions in the binop are
+ // paths and resynthesize new fn call expression instead of using
+ // `ExprKind::Err` placeholder.
+ mk_err_expr(self, inner_op.span.to(self.prev_token.span))
+ }
+ }
+ } else {
+ if !matches!(l1.kind, ExprKind::Lit(_))
+ && !matches!(r1.kind, ExprKind::Lit(_))
+ {
+ // All we know is that this is `foo < bar >` and *nothing* else. Try to
+ // be helpful, but don't attempt to recover.
+ err.help(TURBOFISH_SUGGESTION_STR);
+ err.help("or use `(...)` if you meant to specify fn arguments");
+ }
+
+ // If it looks like a genuine attempt to chain operators (as opposed to a
+ // misformatted turbofish, for instance), suggest a correct form.
+ if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
+ {
+ err.emit();
+ mk_err_expr(self, inner_op.span.to(self.prev_token.span))
+ } else {
+ // These cases cause too many knock-down errors, bail out (#61329).
+ Err(err)
+ }
+ };
+ }
+ let recover =
+ self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
+ err.emit();
+ if recover {
+ return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
+ }
+ }
+ _ => {}
+ }
+ Ok(None)
+ }
+
+ fn consume_fn_args(&mut self) -> Result<(), ()> {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ self.bump(); // `(`
+
+ // Consume the fn call arguments.
+ let modifiers = [
+ (token::OpenDelim(Delimiter::Parenthesis), 1),
+ (token::CloseDelim(Delimiter::Parenthesis), -1),
+ ];
+ self.consume_tts(1, &modifiers);
+
+ if self.token.kind == token::Eof {
+ // Not entirely sure that what we consumed were fn arguments, rollback.
+ self.restore_snapshot(snapshot);
+ Err(())
+ } else {
+ // 99% certain that the suggestion is correct, continue parsing.
+ Ok(())
+ }
+ }
+
+ pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
+ if impl_dyn_multi {
+ self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
+ }
+ }
+
+ /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
+ pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
+ if self.token == token::Question {
+ self.bump();
+ self.struct_span_err(self.prev_token.span, "invalid `?` in type")
+ .span_label(self.prev_token.span, "`?` is only allowed on expressions, not types")
+ .multipart_suggestion(
+ "if you meant to express that the type might not contain a value, use the `Option` wrapper type",
+ vec![
+ (ty.span.shrink_to_lo(), "Option<".to_string()),
+ (self.prev_token.span, ">".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
+ } else {
+ ty
+ }
+ }
+
+ pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
+ // Do not add `+` to expected tokens.
+ if !self.token.is_like_plus() {
+ return Ok(());
+ }
+
+ self.bump(); // `+`
+ let bounds = self.parse_generic_bounds(None)?;
+ let sum_span = ty.span.to(self.prev_token.span);
+
+ let sub = match ty.kind {
+ TyKind::Rptr(ref lifetime, ref mut_ty) => {
+ let sum_with_parens = pprust::to_string(|s| {
+ s.s.word("&");
+ s.print_opt_lifetime(lifetime);
+ s.print_mutability(mut_ty.mutbl, false);
+ s.popen();
+ s.print_type(&mut_ty.ty);
+ if !bounds.is_empty() {
+ s.word(" + ");
+ s.print_type_bounds(&bounds);
+ }
+ s.pclose()
+ });
+
+ BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
+ }
+ TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
+ _ => BadTypePlusSub::ExpectPath { span: sum_span },
+ };
+
+ self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
+
+ Ok(())
+ }
+
+ pub(super) fn recover_from_prefix_increment(
+ &mut self,
+ operand_expr: P<Expr>,
+ op_span: Span,
+ prev_is_semi: bool,
+ ) -> PResult<'a, P<Expr>> {
+ let standalone =
+ if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
+ let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
+
+ self.recover_from_inc_dec(operand_expr, kind, op_span)
+ }
+
+ pub(super) fn recover_from_postfix_increment(
+ &mut self,
+ operand_expr: P<Expr>,
+ op_span: Span,
+ ) -> PResult<'a, P<Expr>> {
+ let kind = IncDecRecovery {
+ standalone: IsStandalone::Maybe,
+ op: IncOrDec::Inc,
+ fixity: UnaryFixity::Post,
+ };
+
+ self.recover_from_inc_dec(operand_expr, kind, op_span)
+ }
+
+ fn recover_from_inc_dec(
+ &mut self,
+ base: P<Expr>,
+ kind: IncDecRecovery,
+ op_span: Span,
+ ) -> PResult<'a, P<Expr>> {
+ let mut err = self.struct_span_err(
+ op_span,
+ &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
+ );
+ err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
+
+ let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
+ err.help(&format!("use `{}= 1` instead", kind.op.chr()));
+ err.emit();
+ Ok(base)
+ };
+
+ // (pre, post)
+ let spans = match kind.fixity {
+ UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
+ UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
+ };
+
+ match kind.standalone {
+ IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
+ IsStandalone::Subexpr => {
+ let Ok(base_src) = self.span_to_snippet(base.span)
+ else { return help_base_case(err, base) };
+ match kind.fixity {
+ UnaryFixity::Pre => {
+ self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+ }
+ UnaryFixity::Post => {
+ self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+ }
+ }
+ }
+ IsStandalone::Maybe => {
+ let Ok(base_src) = self.span_to_snippet(base.span)
+ else { return help_base_case(err, base) };
+ let sugg1 = match kind.fixity {
+ UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
+ UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
+ };
+ let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
+ MultiSugg::emit_many(
+ &mut err,
+ "use `+= 1` instead",
+ Applicability::Unspecified,
+ [sugg1, sugg2].into_iter(),
+ )
+ }
+ }
+ Err(err)
+ }
+
+ fn prefix_inc_dec_suggest(
+ &mut self,
+ base_src: String,
+ kind: IncDecRecovery,
+ (pre_span, post_span): (Span, Span),
+ ) -> MultiSugg {
+ MultiSugg {
+ msg: format!("use `{}= 1` instead", kind.op.chr()),
+ patches: vec![
+ (pre_span, "{ ".to_string()),
+ (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
+ ],
+ applicability: Applicability::MachineApplicable,
+ }
+ }
+
+ fn postfix_inc_dec_suggest(
+ &mut self,
+ base_src: String,
+ kind: IncDecRecovery,
+ (pre_span, post_span): (Span, Span),
+ ) -> MultiSugg {
+ let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
+ MultiSugg {
+ msg: format!("use `{}= 1` instead", kind.op.chr()),
+ patches: vec![
+ (pre_span, format!("{{ let {} = ", tmp_var)),
+ (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
+ ],
+ applicability: Applicability::HasPlaceholders,
+ }
+ }
+
+ fn inc_dec_standalone_suggest(
+ &mut self,
+ kind: IncDecRecovery,
+ (pre_span, post_span): (Span, Span),
+ ) -> MultiSugg {
+ MultiSugg {
+ msg: format!("use `{}= 1` instead", kind.op.chr()),
+ patches: vec![(pre_span, String::new()), (post_span, format!(" {}= 1", kind.op.chr()))],
+ applicability: Applicability::MachineApplicable,
+ }
+ }
+
+ /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
+ /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
+ /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
+ pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
+ &mut self,
+ base: P<T>,
+ ) -> PResult<'a, P<T>> {
+ // Do not add `::` to expected tokens.
+ if self.token == token::ModSep {
+ if let Some(ty) = base.to_ty() {
+ return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
+ }
+ }
+ Ok(base)
+ }
+
+ /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
+ /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
+ pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
+ &mut self,
+ ty_span: Span,
+ ty: P<Ty>,
+ ) -> PResult<'a, P<T>> {
+ self.expect(&token::ModSep)?;
+
+ let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
+ self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
+ path.span = ty_span.to(self.prev_token.span);
+
+ let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
+ self.sess.emit_err(BadQPathStage2 {
+ span: path.span,
+ ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
+ });
+
+ let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
+ Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
+ }
+
+ pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
+ if self.token.kind == TokenKind::Semi {
+ self.bump();
+
+ let mut err =
+ IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
+
+ if !items.is_empty() {
+ let previous_item = &items[items.len() - 1];
+ let previous_item_kind_name = match previous_item.kind {
+ // Say "braced struct" because tuple-structs and
+ // braceless-empty-struct declarations do take a semicolon.
+ ItemKind::Struct(..) => Some("braced struct"),
+ ItemKind::Enum(..) => Some("enum"),
+ ItemKind::Trait(..) => Some("trait"),
+ ItemKind::Union(..) => Some("union"),
+ _ => None,
+ };
+ if let Some(name) = previous_item_kind_name {
+ err.opt_help = Some(());
+ err.name = name;
+ }
+ }
+ self.sess.emit_err(err);
+ true
+ } else {
+ false
+ }
+ }
+
+ /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
+ /// closing delimiter.
+ pub(super) fn unexpected_try_recover(
+ &mut self,
+ t: &TokenKind,
+ ) -> PResult<'a, bool /* recovered */> {
+ let token_str = pprust::token_kind_to_string(t);
+ let this_token_str = super::token_descr(&self.token);
+ let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
+ // Point at the end of the macro call when reaching end of macro arguments.
+ (token::Eof, Some(_)) => {
+ let sp = self.sess.source_map().next_point(self.prev_token.span);
+ (sp, sp)
+ }
+ // We don't want to point at the following span after DUMMY_SP.
+ // This happens when the parser finds an empty TokenStream.
+ _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
+ // EOF, don't want to point at the following char, but rather the last token.
+ (token::Eof, None) => (self.prev_token.span, self.token.span),
+ _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
+ };
+ let msg = format!(
+ "expected `{}`, found {}",
+ token_str,
+ match (&self.token.kind, self.subparser_name) {
+ (token::Eof, Some(origin)) => format!("end of {origin}"),
+ _ => this_token_str,
+ },
+ );
+ let mut err = self.struct_span_err(sp, &msg);
+ let label_exp = format!("expected `{token_str}`");
+ match self.recover_closing_delimiter(&[t.clone()], err) {
+ Err(e) => err = e,
+ Ok(recovered) => {
+ return Ok(recovered);
+ }
+ }
+ let sm = self.sess.source_map();
+ if !sm.is_multiline(prev_sp.until(sp)) {
+ // When the spans are in the same line, it means that the only content
+ // between them is whitespace, point only at the found token.
+ err.span_label(sp, label_exp);
+ } else {
+ err.span_label(prev_sp, label_exp);
+ err.span_label(sp, "unexpected token");
+ }
+ Err(err)
+ }
+
+ pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
+ if self.eat(&token::Semi) {
+ return Ok(());
+ }
+ self.expect(&token::Semi).map(drop) // Error unconditionally
+ }
+
+ /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
+ /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
+ pub(super) fn recover_incorrect_await_syntax(
+ &mut self,
+ lo: Span,
+ await_sp: Span,
+ attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ let (hi, expr, is_question) = if self.token == token::Not {
+ // Handle `await!(<expr>)`.
+ self.recover_await_macro()?
+ } else {
+ self.recover_await_prefix(await_sp)?
+ };
+ let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
+ let kind = match expr.kind {
+ // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
+ // or `foo()?.await` (the very reason we went with postfix syntax 😅).
+ ExprKind::Try(_) => ExprKind::Err,
+ _ => ExprKind::Await(expr),
+ };
+ let expr = self.mk_expr(lo.to(sp), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
+ self.expect(&token::Not)?;
+ self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+ let expr = self.parse_expr()?;
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+ Ok((self.prev_token.span, expr, false))
+ }
+
+ fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
+ let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
+ let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
+ // Handle `await { <expr> }`.
+ // This needs to be handled separately from the next arm to avoid
+ // interpreting `await { <expr> }?` as `<expr>?.await`.
+ self.parse_block_expr(None, self.token.span, BlockCheckMode::Default, AttrVec::new())
+ } else {
+ self.parse_expr()
+ }
+ .map_err(|mut err| {
+ err.span_label(await_sp, "while parsing this incorrect await expression");
+ err
+ })?;
+ Ok((expr.span, expr, is_question))
+ }
+
+ fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
+ let span = lo.to(hi);
+ let applicability = match expr.kind {
+ ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
+ _ => Applicability::MachineApplicable,
+ };
+
+ self.sess.emit_err(IncorrectAwait {
+ span,
+ sugg_span: (span, applicability),
+ expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
+ question_mark: if is_question { "?" } else { "" },
+ });
+
+ span
+ }
+
+ /// If encountering `future.await()`, consumes and emits an error.
+ pub(super) fn recover_from_await_method_call(&mut self) {
+ if self.token == token::OpenDelim(Delimiter::Parenthesis)
+ && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
+ {
+ // future.await()
+ let lo = self.token.span;
+ self.bump(); // (
+ let span = lo.to(self.token.span);
+ self.bump(); // )
+
+ self.sess.emit_err(IncorrectUseOfAwait { span });
+ }
+ }
+
+ pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
+ let is_try = self.token.is_keyword(kw::Try);
+ let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
+ let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
+
+ if is_try && is_questionmark && is_open {
+ let lo = self.token.span;
+ self.bump(); //remove try
+ self.bump(); //remove !
+ let try_span = lo.to(self.token.span); //we take the try!( span
+ self.bump(); //remove (
+ let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
+ self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
+ let hi = self.token.span;
+ self.bump(); //remove )
+ let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
+ err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
+ let prefix = if is_empty { "" } else { "alternatively, " };
+ if !is_empty {
+ err.multipart_suggestion(
+ "you can use the `?` operator instead",
+ vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
+ Applicability::MachineApplicable,
+ );
+ }
+ err.span_suggestion(lo.shrink_to_lo(), &format!("{prefix}you can still access the deprecated `try!()` macro using the \"raw identifier\" syntax"), "r#", Applicability::MachineApplicable);
+ err.emit();
+ Ok(self.mk_expr_err(lo.to(hi)))
+ } else {
+ Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
+ }
+ }
+
+ /// Recovers a situation like `for ( $pat in $expr )`
+ /// and suggest writing `for $pat in $expr` instead.
+ ///
+ /// This should be called before parsing the `$block`.
+ pub(super) fn recover_parens_around_for_head(
+ &mut self,
+ pat: P<Pat>,
+ begin_paren: Option<Span>,
+ ) -> P<Pat> {
+ match (&self.token.kind, begin_paren) {
+ (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
+ self.bump();
+
+ self.struct_span_err(
+ MultiSpan::from_spans(vec![begin_par_sp, self.prev_token.span]),
+ "unexpected parentheses surrounding `for` loop head",
+ )
+ .multipart_suggestion(
+ "remove parentheses in `for` loop",
+ vec![(begin_par_sp, String::new()), (self.prev_token.span, String::new())],
+ // With e.g. `for (x) in y)` this would replace `(x) in y)`
+ // with `x) in y)` which is syntactically invalid.
+ // However, this is prevented before we get here.
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
+ pat.and_then(|pat| match pat.kind {
+ PatKind::Paren(pat) => pat,
+ _ => P(pat),
+ })
+ }
+ _ => pat,
+ }
+ }
+
+ pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
+ (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
+ self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
+ || self.token.is_ident() &&
+ matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
+ !self.token.is_reserved_ident() && // v `foo:bar(baz)`
+ self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
+ || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
+ || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
+ self.look_ahead(2, |t| t == &token::Lt) &&
+ self.look_ahead(3, |t| t.is_ident())
+ || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
+ self.look_ahead(2, |t| t.is_ident())
+ || self.look_ahead(1, |t| t == &token::ModSep)
+ && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
+ self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
+ }
+
+ pub(super) fn recover_seq_parse_error(
+ &mut self,
+ delim: Delimiter,
+ lo: Span,
+ result: PResult<'a, P<Expr>>,
+ ) -> P<Expr> {
+ match result {
+ Ok(x) => x,
+ Err(mut err) => {
+ err.emit();
+ // Recover from parse error, callers expect the closing delim to be consumed.
+ self.consume_block(delim, ConsumeClosingDelim::Yes);
+ self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err, AttrVec::new())
+ }
+ }
+ }
+
+ pub(super) fn recover_closing_delimiter(
+ &mut self,
+ tokens: &[TokenKind],
+ mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
+ ) -> PResult<'a, bool> {
+ let mut pos = None;
+ // We want to use the last closing delim that would apply.
+ for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
+ if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
+ && Some(self.token.span) > unmatched.unclosed_span
+ {
+ pos = Some(i);
+ }
+ }
+ match pos {
+ Some(pos) => {
+ // Recover and assume that the detected unclosed delimiter was meant for
+ // this location. Emit the diagnostic and act as if the delimiter was
+ // present for the parser's sake.
+
+ // Don't attempt to recover from this unclosed delimiter more than once.
+ let unmatched = self.unclosed_delims.remove(pos);
+ let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
+ if unmatched.found_delim.is_none() {
+ // We encountered `Eof`, set this fact here to avoid complaining about missing
+ // `fn main()` when we found place to suggest the closing brace.
+ *self.sess.reached_eof.borrow_mut() = true;
+ }
+
+ // We want to suggest the inclusion of the closing delimiter where it makes
+ // the most sense, which is immediately after the last token:
+ //
+ // {foo(bar {}}
+ // ^ ^
+ // | |
+ // | help: `)` may belong here
+ // |
+ // unclosed delimiter
+ if let Some(sp) = unmatched.unclosed_span {
+ let mut primary_span: Vec<Span> =
+ err.span.primary_spans().iter().cloned().collect();
+ primary_span.push(sp);
+ let mut primary_span: MultiSpan = primary_span.into();
+ for span_label in err.span.span_labels() {
+ if let Some(label) = span_label.label {
+ primary_span.push_span_label(span_label.span, label);
+ }
+ }
+ err.set_span(primary_span);
+ err.span_label(sp, "unclosed delimiter");
+ }
+ // Backticks should be removed to apply suggestions.
+ let mut delim = delim.to_string();
+ delim.retain(|c| c != '`');
+ err.span_suggestion_short(
+ self.prev_token.span.shrink_to_hi(),
+ &format!("`{delim}` may belong here"),
+ delim,
+ Applicability::MaybeIncorrect,
+ );
+ if unmatched.found_delim.is_none() {
+ // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
+ // errors which would be emitted elsewhere in the parser and let other error
+ // recovery consume the rest of the file.
+ Err(err)
+ } else {
+ err.emit();
+ self.expected_tokens.clear(); // Reduce the number of errors.
+ Ok(true)
+ }
+ }
+ _ => Err(err),
+ }
+ }
+
+ /// Eats tokens until we can be relatively sure we reached the end of the
+ /// statement. This is something of a best-effort heuristic.
+ ///
+ /// We terminate when we find an unmatched `}` (without consuming it).
+ pub(super) fn recover_stmt(&mut self) {
+ self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
+ }
+
+ /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
+ /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
+ /// approximate -- it can mean we break too early due to macros, but that
+ /// should only lead to sub-optimal recovery, not inaccurate parsing).
+ ///
+ /// If `break_on_block` is `Break`, then we will stop consuming tokens
+ /// after finding (and consuming) a brace-delimited block.
+ pub(super) fn recover_stmt_(
+ &mut self,
+ break_on_semi: SemiColonMode,
+ break_on_block: BlockMode,
+ ) {
+ let mut brace_depth = 0;
+ let mut bracket_depth = 0;
+ let mut in_block = false;
+ debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
+ loop {
+ debug!("recover_stmt_ loop {:?}", self.token);
+ match self.token.kind {
+ token::OpenDelim(Delimiter::Brace) => {
+ brace_depth += 1;
+ self.bump();
+ if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
+ {
+ in_block = true;
+ }
+ }
+ token::OpenDelim(Delimiter::Bracket) => {
+ bracket_depth += 1;
+ self.bump();
+ }
+ token::CloseDelim(Delimiter::Brace) => {
+ if brace_depth == 0 {
+ debug!("recover_stmt_ return - close delim {:?}", self.token);
+ break;
+ }
+ brace_depth -= 1;
+ self.bump();
+ if in_block && bracket_depth == 0 && brace_depth == 0 {
+ debug!("recover_stmt_ return - block end {:?}", self.token);
+ break;
+ }
+ }
+ token::CloseDelim(Delimiter::Bracket) => {
+ bracket_depth -= 1;
+ if bracket_depth < 0 {
+ bracket_depth = 0;
+ }
+ self.bump();
+ }
+ token::Eof => {
+ debug!("recover_stmt_ return - Eof");
+ break;
+ }
+ token::Semi => {
+ self.bump();
+ if break_on_semi == SemiColonMode::Break
+ && brace_depth == 0
+ && bracket_depth == 0
+ {
+ debug!("recover_stmt_ return - Semi");
+ break;
+ }
+ }
+ token::Comma
+ if break_on_semi == SemiColonMode::Comma
+ && brace_depth == 0
+ && bracket_depth == 0 =>
+ {
+ debug!("recover_stmt_ return - Semi");
+ break;
+ }
+ _ => self.bump(),
+ }
+ }
+ }
+
+ pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
+ if self.eat_keyword(kw::In) {
+ // a common typo: `for _ in in bar {}`
+ self.sess.emit_err(InInTypo {
+ span: self.prev_token.span,
+ sugg_span: in_span.until(self.prev_token.span),
+ });
+ }
+ }
+
+ pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
+ if let token::DocComment(..) = self.token.kind {
+ self.struct_span_err(
+ self.token.span,
+ "documentation comments cannot be applied to a function parameter's type",
+ )
+ .span_label(self.token.span, "doc comments are not allowed here")
+ .emit();
+ self.bump();
+ } else if self.token == token::Pound
+ && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
+ {
+ let lo = self.token.span;
+ // Skip every token until next possible arg.
+ while self.token != token::CloseDelim(Delimiter::Bracket) {
+ self.bump();
+ }
+ let sp = lo.to(self.token.span);
+ self.bump();
+ self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
+ .span_label(sp, "attributes are not allowed here")
+ .emit();
+ }
+ }
+
+ pub(super) fn parameter_without_type(
+ &mut self,
+ err: &mut Diagnostic,
+ pat: P<ast::Pat>,
+ require_name: bool,
+ first_param: bool,
+ ) -> Option<Ident> {
+ // If we find a pattern followed by an identifier, it could be an (incorrect)
+ // C-style parameter declaration.
+ if self.check_ident()
+ && self.look_ahead(1, |t| {
+ *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
+ })
+ {
+ // `fn foo(String s) {}`
+ let ident = self.parse_ident().unwrap();
+ let span = pat.span.with_hi(ident.span.hi());
+
+ err.span_suggestion(
+ span,
+ "declare the type after the parameter binding",
+ "<identifier>: <type>",
+ Applicability::HasPlaceholders,
+ );
+ return Some(ident);
+ } else if require_name
+ && (self.token == token::Comma
+ || self.token == token::Lt
+ || self.token == token::CloseDelim(Delimiter::Parenthesis))
+ {
+ let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
+
+ let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
+ match pat.kind {
+ PatKind::Ident(_, ident, _) => (
+ ident,
+ "self: ",
+ ": TypeName".to_string(),
+ "_: ",
+ pat.span.shrink_to_lo(),
+ pat.span.shrink_to_hi(),
+ pat.span.shrink_to_lo(),
+ ),
+ // Also catches `fn foo(&a)`.
+ PatKind::Ref(ref inner_pat, mutab)
+ if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
+ {
+ match inner_pat.clone().into_inner().kind {
+ PatKind::Ident(_, ident, _) => {
+ let mutab = mutab.prefix_str();
+ (
+ ident,
+ "self: ",
+ format!("{ident}: &{mutab}TypeName"),
+ "_: ",
+ pat.span.shrink_to_lo(),
+ pat.span,
+ pat.span.shrink_to_lo(),
+ )
+ }
+ _ => unreachable!(),
+ }
+ }
+ _ => {
+ // Otherwise, try to get a type and emit a suggestion.
+ if let Some(ty) = pat.to_ty() {
+ err.span_suggestion_verbose(
+ pat.span,
+ "explicitly ignore the parameter name",
+ format!("_: {}", pprust::ty_to_string(&ty)),
+ Applicability::MachineApplicable,
+ );
+ err.note(rfc_note);
+ }
+
+ return None;
+ }
+ };
+
+ // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
+ if first_param {
+ err.span_suggestion(
+ self_span,
+ "if this is a `self` type, give it a parameter name",
+ self_sugg,
+ Applicability::MaybeIncorrect,
+ );
+ }
+ // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
+ // `fn foo(HashMap: TypeName<u32>)`.
+ if self.token != token::Lt {
+ err.span_suggestion(
+ param_span,
+ "if this is a parameter name, give it a type",
+ param_sugg,
+ Applicability::HasPlaceholders,
+ );
+ }
+ err.span_suggestion(
+ type_span,
+ "if this is a type, explicitly ignore the parameter name",
+ type_sugg,
+ Applicability::MachineApplicable,
+ );
+ err.note(rfc_note);
+
+ // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
+ return if self.token == token::Lt { None } else { Some(ident) };
+ }
+ None
+ }
+
+ pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
+ let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
+ self.expect(&token::Colon)?;
+ let ty = self.parse_ty()?;
+
+ struct_span_err!(
+ self.diagnostic(),
+ pat.span,
+ E0642,
+ "patterns aren't allowed in methods without bodies",
+ )
+ .span_suggestion_short(
+ pat.span,
+ "give this argument a name or use an underscore to ignore it",
+ "_",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
+ let pat =
+ P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
+ Ok((pat, ty))
+ }
+
+ pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
+ let sp = param.pat.span;
+ param.ty.kind = TyKind::Err;
+ self.struct_span_err(sp, "unexpected `self` parameter in function")
+ .span_label(sp, "must be the first parameter of an associated function")
+ .emit();
+ Ok(param)
+ }
+
+ pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
+ let mut brace_depth = 0;
+ loop {
+ if self.eat(&token::OpenDelim(delim)) {
+ brace_depth += 1;
+ } else if self.check(&token::CloseDelim(delim)) {
+ if brace_depth == 0 {
+ if let ConsumeClosingDelim::Yes = consume_close {
+ // Some of the callers of this method expect to be able to parse the
+ // closing delimiter themselves, so we leave it alone. Otherwise we advance
+ // the parser.
+ self.bump();
+ }
+ return;
+ } else {
+ self.bump();
+ brace_depth -= 1;
+ continue;
+ }
+ } else if self.token == token::Eof {
+ return;
+ } else {
+ self.bump();
+ }
+ }
+ }
+
+ pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let (span, msg) = match (&self.token.kind, self.subparser_name) {
+ (&token::Eof, Some(origin)) => {
+ let sp = self.sess.source_map().next_point(self.prev_token.span);
+ (sp, format!("expected expression, found end of {origin}"))
+ }
+ _ => (
+ self.token.span,
+ format!("expected expression, found {}", super::token_descr(&self.token),),
+ ),
+ };
+ let mut err = self.struct_span_err(span, &msg);
+ let sp = self.sess.source_map().start_point(self.token.span);
+ if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
+ self.sess.expr_parentheses_needed(&mut err, *sp);
+ }
+ err.span_label(span, "expected expression");
+ err
+ }
+
+ fn consume_tts(
+ &mut self,
+ mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
+ // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
+ modifier: &[(token::TokenKind, i64)],
+ ) {
+ while acc > 0 {
+ if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
+ acc += *val;
+ }
+ if self.token.kind == token::Eof {
+ break;
+ }
+ self.bump();
+ }
+ }
+
+ /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
+ ///
+ /// This is necessary because at this point we don't know whether we parsed a function with
+ /// anonymous parameters or a function with names but no types. In order to minimize
+ /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
+ /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
+ /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
+ /// we deduplicate them to not complain about duplicated parameter names.
+ pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
+ let mut seen_inputs = FxHashSet::default();
+ for input in fn_inputs.iter_mut() {
+ let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
+ (&input.pat.kind, &input.ty.kind)
+ {
+ Some(*ident)
+ } else {
+ None
+ };
+ if let Some(ident) = opt_ident {
+ if seen_inputs.contains(&ident) {
+ input.pat.kind = PatKind::Wild;
+ }
+ seen_inputs.insert(ident);
+ }
+ }
+ }
+
+ /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
+ /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
+ /// like the user has forgotten them.
+ pub fn handle_ambiguous_unbraced_const_arg(
+ &mut self,
+ args: &mut Vec<AngleBracketedArg>,
+ ) -> PResult<'a, bool> {
+ // If we haven't encountered a closing `>`, then the argument is malformed.
+ // It's likely that the user has written a const expression without enclosing it
+ // in braces, so we try to recover here.
+ let arg = args.pop().unwrap();
+ // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
+ // adverse side-effects to subsequent errors and seems to advance the parser.
+ // We are causing this error here exclusively in case that a `const` expression
+ // could be recovered from the current parser state, even if followed by more
+ // arguments after a comma.
+ let mut err = self.struct_span_err(
+ self.token.span,
+ &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
+ );
+ err.span_label(self.token.span, "expected one of `,` or `>`");
+ match self.recover_const_arg(arg.span(), err) {
+ Ok(arg) => {
+ args.push(AngleBracketedArg::Arg(arg));
+ if self.eat(&token::Comma) {
+ return Ok(true); // Continue
+ }
+ }
+ Err(mut err) => {
+ args.push(arg);
+ // We will emit a more generic error later.
+ err.delay_as_bug();
+ }
+ }
+ return Ok(false); // Don't continue.
+ }
+
+ /// Attempt to parse a generic const argument that has not been enclosed in braces.
+ /// There are a limited number of expressions that are permitted without being encoded
+ /// in braces:
+ /// - Literals.
+ /// - Single-segment paths (i.e. standalone generic const parameters).
+ /// All other expressions that can be parsed will emit an error suggesting the expression be
+ /// wrapped in braces.
+ pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
+ let start = self.token.span;
+ let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
+ err.span_label(
+ start.shrink_to_lo(),
+ "while parsing a const generic argument starting here",
+ );
+ err
+ })?;
+ if !self.expr_is_valid_const_arg(&expr) {
+ self.struct_span_err(
+ expr.span,
+ "expressions must be enclosed in braces to be used as const generic \
+ arguments",
+ )
+ .multipart_suggestion(
+ "enclose the `const` expression in braces",
+ vec![
+ (expr.span.shrink_to_lo(), "{ ".to_string()),
+ (expr.span.shrink_to_hi(), " }".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+ Ok(expr)
+ }
+
+ fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ let param = match self.parse_const_param(vec![]) {
+ Ok(param) => param,
+ Err(err) => {
+ err.cancel();
+ self.restore_snapshot(snapshot);
+ return None;
+ }
+ };
+ let mut err =
+ self.struct_span_err(param.span(), "unexpected `const` parameter declaration");
+ err.span_label(param.span(), "expected a `const` expression, not a parameter declaration");
+ if let (Some(generics), Ok(snippet)) =
+ (ty_generics, self.sess.source_map().span_to_snippet(param.span()))
+ {
+ let (span, sugg) = match &generics.params[..] {
+ [] => (generics.span, format!("<{snippet}>")),
+ [.., generic] => (generic.span().shrink_to_hi(), format!(", {snippet}")),
+ };
+ err.multipart_suggestion(
+ "`const` parameters must be declared for the `impl`",
+ vec![(span, sugg), (param.span(), param.ident.to_string())],
+ Applicability::MachineApplicable,
+ );
+ }
+ let value = self.mk_expr_err(param.span());
+ err.emit();
+ Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
+ }
+
+ pub fn recover_const_param_declaration(
+ &mut self,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Option<GenericArg>> {
+ // We have to check for a few different cases.
+ if let Some(arg) = self.recover_const_param_decl(ty_generics) {
+ return Ok(Some(arg));
+ }
+
+ // We haven't consumed `const` yet.
+ let start = self.token.span;
+ self.bump(); // `const`
+
+ // Detect and recover from the old, pre-RFC2000 syntax for const generics.
+ let mut err = self
+ .struct_span_err(start, "expected lifetime, type, or constant, found keyword `const`");
+ if self.check_const_arg() {
+ err.span_suggestion_verbose(
+ start.until(self.token.span),
+ "the `const` keyword is only needed in the definition of the type",
+ "",
+ Applicability::MaybeIncorrect,
+ );
+ err.emit();
+ Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
+ } else {
+ let after_kw_const = self.token.span;
+ self.recover_const_arg(after_kw_const, err).map(Some)
+ }
+ }
+
+ /// Try to recover from possible generic const argument without `{` and `}`.
+ ///
+ /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
+ /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
+ /// if we think that that the resulting expression would be well formed.
+ pub fn recover_const_arg(
+ &mut self,
+ start: Span,
+ mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
+ ) -> PResult<'a, GenericArg> {
+ let is_op_or_dot = AssocOp::from_token(&self.token)
+ .and_then(|op| {
+ if let AssocOp::Greater
+ | AssocOp::Less
+ | AssocOp::ShiftRight
+ | AssocOp::GreaterEqual
+ // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
+ // assign a value to a defaulted generic parameter.
+ | AssocOp::Assign
+ | AssocOp::AssignOp(_) = op
+ {
+ None
+ } else {
+ Some(op)
+ }
+ })
+ .is_some()
+ || self.token.kind == TokenKind::Dot;
+ // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
+ // type params has been parsed.
+ let was_op =
+ matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
+ if !is_op_or_dot && !was_op {
+ // We perform these checks and early return to avoid taking a snapshot unnecessarily.
+ return Err(err);
+ }
+ let snapshot = self.create_snapshot_for_diagnostic();
+ if is_op_or_dot {
+ self.bump();
+ }
+ match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
+ Ok(expr) => {
+ // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
+ if token::EqEq == snapshot.token.kind {
+ err.span_suggestion(
+ snapshot.token.span,
+ "if you meant to use an associated type binding, replace `==` with `=`",
+ "=",
+ Applicability::MaybeIncorrect,
+ );
+ let value = self.mk_expr_err(start.to(expr.span));
+ err.emit();
+ return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
+ } else if token::Colon == snapshot.token.kind
+ && expr.span.lo() == snapshot.token.span.hi()
+ && matches!(expr.kind, ExprKind::Path(..))
+ {
+ // Find a mistake like "foo::var:A".
+ err.span_suggestion(
+ snapshot.token.span,
+ "write a path separator here",
+ "::",
+ Applicability::MaybeIncorrect,
+ );
+ err.emit();
+ return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
+ } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
+ {
+ // Avoid the following output by checking that we consumed a full const arg:
+ // help: expressions must be enclosed in braces to be used as const generic
+ // arguments
+ // |
+ // LL | let sr: Vec<{ (u32, _, _) = vec![] };
+ // | ^ ^
+ return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
+ }
+ }
+ Err(err) => {
+ err.cancel();
+ }
+ }
+ self.restore_snapshot(snapshot);
+ Err(err)
+ }
+
+ /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
+ pub fn dummy_const_arg_needs_braces(
+ &self,
+ mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
+ span: Span,
+ ) -> GenericArg {
+ err.multipart_suggestion(
+ "expressions must be enclosed in braces to be used as const generic \
+ arguments",
+ vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
+ Applicability::MaybeIncorrect,
+ );
+ let value = self.mk_expr_err(span);
+ err.emit();
+ GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
+ }
+
+ /// Get the diagnostics for the cases where `move async` is found.
+ ///
+ /// `move_async_span` starts at the 'm' of the move keyword and ends with the 'c' of the async keyword
+ pub(super) fn incorrect_move_async_order_found(
+ &self,
+ move_async_span: Span,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let mut err =
+ self.struct_span_err(move_async_span, "the order of `move` and `async` is incorrect");
+ err.span_suggestion_verbose(
+ move_async_span,
+ "try switching the order",
+ "async move",
+ Applicability::MaybeIncorrect,
+ );
+ err
+ }
+
+ /// Some special error handling for the "top-level" patterns in a match arm,
+ /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
+ pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
+ &mut self,
+ mut first_pat: P<Pat>,
+ expected: Expected,
+ ) -> P<Pat> {
+ if token::Colon != self.token.kind {
+ return first_pat;
+ }
+ if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
+ || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
+ {
+ return first_pat;
+ }
+ // The pattern looks like it might be a path with a `::` -> `:` typo:
+ // `match foo { bar:baz => {} }`
+ let span = self.token.span;
+ // We only emit "unexpected `:`" error here if we can successfully parse the
+ // whole pattern correctly in that case.
+ let snapshot = self.create_snapshot_for_diagnostic();
+
+ // Create error for "unexpected `:`".
+ match self.expected_one_of_not_found(&[], &[]) {
+ Err(mut err) => {
+ self.bump(); // Skip the `:`.
+ match self.parse_pat_no_top_alt(expected) {
+ Err(inner_err) => {
+ // Carry on as if we had not done anything, callers will emit a
+ // reasonable error.
+ inner_err.cancel();
+ err.cancel();
+ self.restore_snapshot(snapshot);
+ }
+ Ok(mut pat) => {
+ // We've parsed the rest of the pattern.
+ let new_span = first_pat.span.to(pat.span);
+ let mut show_sugg = false;
+ // Try to construct a recovered pattern.
+ match &mut pat.kind {
+ PatKind::Struct(qself @ None, path, ..)
+ | PatKind::TupleStruct(qself @ None, path, _)
+ | PatKind::Path(qself @ None, path) => match &first_pat.kind {
+ PatKind::Ident(_, ident, _) => {
+ path.segments.insert(0, PathSegment::from_ident(*ident));
+ path.span = new_span;
+ show_sugg = true;
+ first_pat = pat;
+ }
+ PatKind::Path(old_qself, old_path) => {
+ path.segments = old_path
+ .segments
+ .iter()
+ .cloned()
+ .chain(take(&mut path.segments))
+ .collect();
+ path.span = new_span;
+ *qself = old_qself.clone();
+ first_pat = pat;
+ show_sugg = true;
+ }
+ _ => {}
+ },
+ PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None) => {
+ match &first_pat.kind {
+ PatKind::Ident(_, old_ident, _) => {
+ let path = PatKind::Path(
+ None,
+ Path {
+ span: new_span,
+ segments: vec![
+ PathSegment::from_ident(*old_ident),
+ PathSegment::from_ident(*ident),
+ ],
+ tokens: None,
+ },
+ );
+ first_pat = self.mk_pat(new_span, path);
+ show_sugg = true;
+ }
+ PatKind::Path(old_qself, old_path) => {
+ let mut segments = old_path.segments.clone();
+ segments.push(PathSegment::from_ident(*ident));
+ let path = PatKind::Path(
+ old_qself.clone(),
+ Path { span: new_span, segments, tokens: None },
+ );
+ first_pat = self.mk_pat(new_span, path);
+ show_sugg = true;
+ }
+ _ => {}
+ }
+ }
+ _ => {}
+ }
+ if show_sugg {
+ err.span_suggestion(
+ span,
+ "maybe write a path separator here",
+ "::",
+ Applicability::MaybeIncorrect,
+ );
+ } else {
+ first_pat = self.mk_pat(new_span, PatKind::Wild);
+ }
+ err.emit();
+ }
+ }
+ }
+ _ => {
+ // Carry on as if we had not done anything. This should be unreachable.
+ self.restore_snapshot(snapshot);
+ }
+ };
+ first_pat
+ }
+
+ pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
+ let Some(label) = self.eat_label().filter(|_| {
+ self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
+ }) else {
+ return false;
+ };
+ let span = label.ident.span.to(self.prev_token.span);
+ let mut err = self.struct_span_err(span, "block label not supported here");
+ err.span_label(span, "not supported here");
+ err.tool_only_span_suggestion(
+ label.ident.span.until(self.token.span),
+ "remove this block label",
+ "",
+ Applicability::MachineApplicable,
+ );
+ err.emit();
+ true
+ }
+
+ /// Some special error handling for the "top-level" patterns in a match arm,
+ /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
+ pub(crate) fn maybe_recover_unexpected_comma(
+ &mut self,
+ lo: Span,
+ rt: CommaRecoveryMode,
+ ) -> PResult<'a, ()> {
+ if self.token != token::Comma {
+ return Ok(());
+ }
+
+ // An unexpected comma after a top-level pattern is a clue that the
+ // user (perhaps more accustomed to some other language) forgot the
+ // parentheses in what should have been a tuple pattern; return a
+ // suggestion-enhanced error here rather than choking on the comma later.
+ let comma_span = self.token.span;
+ self.bump();
+ if let Err(err) = self.skip_pat_list() {
+ // We didn't expect this to work anyway; we just wanted to advance to the
+ // end of the comma-sequence so we know the span to suggest parenthesizing.
+ err.cancel();
+ }
+ let seq_span = lo.to(self.prev_token.span);
+ let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
+ if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
+ err.multipart_suggestion(
+ &format!(
+ "try adding parentheses to match on a tuple{}",
+ if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
+ ),
+ vec![
+ (seq_span.shrink_to_lo(), "(".to_string()),
+ (seq_span.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ );
+ if let CommaRecoveryMode::EitherTupleOrPipe = rt {
+ err.span_suggestion(
+ seq_span,
+ "...or a vertical bar to match on multiple alternatives",
+ seq_snippet.replace(',', " |"),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ Err(err)
+ }
+
+ pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
+ let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
+ let qself_position = qself.as_ref().map(|qself| qself.position);
+ for (i, segments) in path.segments.windows(2).enumerate() {
+ if qself_position.map(|pos| i < pos).unwrap_or(false) {
+ continue;
+ }
+ if let [a, b] = segments {
+ let (a_span, b_span) = (a.span(), b.span());
+ let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
+ if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
+ let mut err = self.struct_span_err(
+ path.span.shrink_to_hi(),
+ "expected `:` followed by trait or lifetime",
+ );
+ err.span_suggestion(
+ between_span,
+ "use single colon",
+ ": ",
+ Applicability::MachineApplicable,
+ );
+ return Err(err);
+ }
+ }
+ }
+ Ok(())
+ }
+
+ /// Parse and throw away a parenthesized comma separated
+ /// sequence of patterns until `)` is reached.
+ fn skip_pat_list(&mut self) -> PResult<'a, ()> {
+ while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
+ self.parse_pat_no_top_alt(None)?;
+ if !self.eat(&token::Comma) {
+ return Ok(());
+ }
+ }
+ Ok(())
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
new file mode 100644
index 000000000..0719a0ef0
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -0,0 +1,3288 @@
+use super::diagnostics::SnapshotParser;
+use super::pat::{CommaRecoveryMode, RecoverColon, RecoverComma, PARAM_EXPECTED};
+use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
+use super::{
+ AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
+ SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
+};
+use crate::maybe_recover_from_interpolated_ty_qpath;
+
+use core::mem;
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::tokenstream::Spacing;
+use rustc_ast::util::classify;
+use rustc_ast::util::literal::LitError;
+use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
+use rustc_ast::visit::Visitor;
+use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
+use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
+use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
+use rustc_ast::{ClosureBinder, StmtKind};
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::thin_vec::ThinVec;
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult};
+use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
+use rustc_session::lint::BuiltinLintDiagnostics;
+use rustc_span::source_map::{self, Span, Spanned};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{BytePos, Pos};
+
+/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
+/// dropped into the token stream, which happens while parsing the result of
+/// macro expansion). Placement of these is not as complex as I feared it would
+/// be. The important thing is to make sure that lookahead doesn't balk at
+/// `token::Interpolated` tokens.
+macro_rules! maybe_whole_expr {
+ ($p:expr) => {
+ if let token::Interpolated(nt) = &$p.token.kind {
+ match &**nt {
+ token::NtExpr(e) | token::NtLiteral(e) => {
+ let e = e.clone();
+ $p.bump();
+ return Ok(e);
+ }
+ token::NtPath(path) => {
+ let path = (**path).clone();
+ $p.bump();
+ return Ok($p.mk_expr(
+ $p.prev_token.span,
+ ExprKind::Path(None, path),
+ AttrVec::new(),
+ ));
+ }
+ token::NtBlock(block) => {
+ let block = block.clone();
+ $p.bump();
+ return Ok($p.mk_expr(
+ $p.prev_token.span,
+ ExprKind::Block(block, None),
+ AttrVec::new(),
+ ));
+ }
+ _ => {}
+ };
+ }
+ };
+}
+
+#[derive(Debug)]
+pub(super) enum LhsExpr {
+ NotYetParsed,
+ AttributesParsed(AttrWrapper),
+ AlreadyParsed(P<Expr>),
+}
+
+impl From<Option<AttrWrapper>> for LhsExpr {
+ /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
+ /// and `None` into `LhsExpr::NotYetParsed`.
+ ///
+ /// This conversion does not allocate.
+ fn from(o: Option<AttrWrapper>) -> Self {
+ if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
+ }
+}
+
+impl From<P<Expr>> for LhsExpr {
+ /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
+ ///
+ /// This conversion does not allocate.
+ fn from(expr: P<Expr>) -> Self {
+ LhsExpr::AlreadyParsed(expr)
+ }
+}
+
+impl<'a> Parser<'a> {
+ /// Parses an expression.
+ #[inline]
+ pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
+ self.current_closure.take();
+
+ self.parse_expr_res(Restrictions::empty(), None)
+ }
+
+ /// Parses an expression, forcing tokens to be collected
+ pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
+ self.collect_tokens_no_attrs(|this| this.parse_expr())
+ }
+
+ pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
+ self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
+ }
+
+ fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
+ match self.parse_expr() {
+ Ok(expr) => Ok(expr),
+ Err(mut err) => match self.token.ident() {
+ Some((Ident { name: kw::Underscore, .. }, false))
+ if self.look_ahead(1, |t| t == &token::Comma) =>
+ {
+ // Special-case handling of `foo(_, _, _)`
+ err.emit();
+ self.bump();
+ Ok(self.mk_expr(self.prev_token.span, ExprKind::Err, AttrVec::new()))
+ }
+ _ => Err(err),
+ },
+ }
+ }
+
+ /// Parses a sequence of expressions delimited by parentheses.
+ fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
+ self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
+ }
+
+ /// Parses an expression, subject to the given restrictions.
+ #[inline]
+ pub(super) fn parse_expr_res(
+ &mut self,
+ r: Restrictions,
+ already_parsed_attrs: Option<AttrWrapper>,
+ ) -> PResult<'a, P<Expr>> {
+ self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
+ }
+
+ /// Parses an associative expression.
+ ///
+ /// This parses an expression accounting for associativity and precedence of the operators in
+ /// the expression.
+ #[inline]
+ fn parse_assoc_expr(
+ &mut self,
+ already_parsed_attrs: Option<AttrWrapper>,
+ ) -> PResult<'a, P<Expr>> {
+ self.parse_assoc_expr_with(0, already_parsed_attrs.into())
+ }
+
+ /// Parses an associative expression with operators of at least `min_prec` precedence.
+ pub(super) fn parse_assoc_expr_with(
+ &mut self,
+ min_prec: usize,
+ lhs: LhsExpr,
+ ) -> PResult<'a, P<Expr>> {
+ let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
+ expr
+ } else {
+ let attrs = match lhs {
+ LhsExpr::AttributesParsed(attrs) => Some(attrs),
+ _ => None,
+ };
+ if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
+ return self.parse_prefix_range_expr(attrs);
+ } else {
+ self.parse_prefix_expr(attrs)?
+ }
+ };
+ let last_type_ascription_set = self.last_type_ascription.is_some();
+
+ if !self.should_continue_as_assoc_expr(&lhs) {
+ self.last_type_ascription = None;
+ return Ok(lhs);
+ }
+
+ self.expected_tokens.push(TokenType::Operator);
+ while let Some(op) = self.check_assoc_op() {
+ // Adjust the span for interpolated LHS to point to the `$lhs` token
+ // and not to what it refers to.
+ let lhs_span = match self.prev_token.kind {
+ TokenKind::Interpolated(..) => self.prev_token.span,
+ _ => lhs.span,
+ };
+
+ let cur_op_span = self.token.span;
+ let restrictions = if op.node.is_assign_like() {
+ self.restrictions & Restrictions::NO_STRUCT_LITERAL
+ } else {
+ self.restrictions
+ };
+ let prec = op.node.precedence();
+ if prec < min_prec {
+ break;
+ }
+ // Check for deprecated `...` syntax
+ if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
+ self.err_dotdotdot_syntax(self.token.span);
+ }
+
+ if self.token == token::LArrow {
+ self.err_larrow_operator(self.token.span);
+ }
+
+ self.bump();
+ if op.node.is_comparison() {
+ if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
+ return Ok(expr);
+ }
+ }
+
+ // Look for JS' `===` and `!==` and recover
+ if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
+ && self.token.kind == token::Eq
+ && self.prev_token.span.hi() == self.token.span.lo()
+ {
+ let sp = op.span.to(self.token.span);
+ let sugg = match op.node {
+ AssocOp::Equal => "==",
+ AssocOp::NotEqual => "!=",
+ _ => unreachable!(),
+ };
+ self.struct_span_err(sp, &format!("invalid comparison operator `{sugg}=`"))
+ .span_suggestion_short(
+ sp,
+ &format!("`{s}=` is not a valid comparison operator, use `{s}`", s = sugg),
+ sugg,
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ self.bump();
+ }
+
+ // Look for PHP's `<>` and recover
+ if op.node == AssocOp::Less
+ && self.token.kind == token::Gt
+ && self.prev_token.span.hi() == self.token.span.lo()
+ {
+ let sp = op.span.to(self.token.span);
+ self.struct_span_err(sp, "invalid comparison operator `<>`")
+ .span_suggestion_short(
+ sp,
+ "`<>` is not a valid comparison operator, use `!=`",
+ "!=",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ self.bump();
+ }
+
+ // Look for C++'s `<=>` and recover
+ if op.node == AssocOp::LessEqual
+ && self.token.kind == token::Gt
+ && self.prev_token.span.hi() == self.token.span.lo()
+ {
+ let sp = op.span.to(self.token.span);
+ self.struct_span_err(sp, "invalid comparison operator `<=>`")
+ .span_label(
+ sp,
+ "`<=>` is not a valid comparison operator, use `std::cmp::Ordering`",
+ )
+ .emit();
+ self.bump();
+ }
+
+ if self.prev_token == token::BinOp(token::Plus)
+ && self.token == token::BinOp(token::Plus)
+ && self.prev_token.span.between(self.token.span).is_empty()
+ {
+ let op_span = self.prev_token.span.to(self.token.span);
+ // Eat the second `+`
+ self.bump();
+ lhs = self.recover_from_postfix_increment(lhs, op_span)?;
+ continue;
+ }
+
+ let op = op.node;
+ // Special cases:
+ if op == AssocOp::As {
+ lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+ continue;
+ } else if op == AssocOp::Colon {
+ lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
+ continue;
+ } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
+ // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
+ // generalise it to the Fixity::None code.
+ lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
+ break;
+ }
+
+ let fixity = op.fixity();
+ let prec_adjustment = match fixity {
+ Fixity::Right => 0,
+ Fixity::Left => 1,
+ // We currently have no non-associative operators that are not handled above by
+ // the special cases. The code is here only for future convenience.
+ Fixity::None => 1,
+ };
+ let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
+ this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
+ })?;
+
+ let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
+ lhs = match op {
+ AssocOp::Add
+ | AssocOp::Subtract
+ | AssocOp::Multiply
+ | AssocOp::Divide
+ | AssocOp::Modulus
+ | AssocOp::LAnd
+ | AssocOp::LOr
+ | AssocOp::BitXor
+ | AssocOp::BitAnd
+ | AssocOp::BitOr
+ | AssocOp::ShiftLeft
+ | AssocOp::ShiftRight
+ | AssocOp::Equal
+ | AssocOp::Less
+ | AssocOp::LessEqual
+ | AssocOp::NotEqual
+ | AssocOp::Greater
+ | AssocOp::GreaterEqual => {
+ let ast_op = op.to_ast_binop().unwrap();
+ let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
+ self.mk_expr(span, binary, AttrVec::new())
+ }
+ AssocOp::Assign => {
+ self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
+ }
+ AssocOp::AssignOp(k) => {
+ let aop = match k {
+ token::Plus => BinOpKind::Add,
+ token::Minus => BinOpKind::Sub,
+ token::Star => BinOpKind::Mul,
+ token::Slash => BinOpKind::Div,
+ token::Percent => BinOpKind::Rem,
+ token::Caret => BinOpKind::BitXor,
+ token::And => BinOpKind::BitAnd,
+ token::Or => BinOpKind::BitOr,
+ token::Shl => BinOpKind::Shl,
+ token::Shr => BinOpKind::Shr,
+ };
+ let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
+ self.mk_expr(span, aopexpr, AttrVec::new())
+ }
+ AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
+ self.span_bug(span, "AssocOp should have been handled by special case")
+ }
+ };
+
+ if let Fixity::None = fixity {
+ break;
+ }
+ }
+ if last_type_ascription_set {
+ self.last_type_ascription = None;
+ }
+ Ok(lhs)
+ }
+
+ fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
+ match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
+ // Semi-statement forms are odd:
+ // See https://github.com/rust-lang/rust/issues/29071
+ (true, None) => false,
+ (false, _) => true, // Continue parsing the expression.
+ // An exhaustive check is done in the following block, but these are checked first
+ // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
+ // want to keep their span info to improve diagnostics in these cases in a later stage.
+ (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
+ (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
+ (true, Some(AssocOp::Add)) // `{ 42 } + 42
+ // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
+ // `if x { a } else { b } && if y { c } else { d }`
+ if !self.look_ahead(1, |t| t.is_used_keyword()) => {
+ // These cases are ambiguous and can't be identified in the parser alone.
+ let sp = self.sess.source_map().start_point(self.token.span);
+ self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
+ false
+ }
+ (true, Some(AssocOp::LAnd)) |
+ (true, Some(AssocOp::LOr)) |
+ (true, Some(AssocOp::BitOr)) => {
+ // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
+ // above due to #74233.
+ // These cases are ambiguous and can't be identified in the parser alone.
+ //
+ // Bitwise AND is left out because guessing intent is hard. We can make
+ // suggestions based on the assumption that double-refs are rarely intentional,
+ // and closures are distinct enough that they don't get mixed up with their
+ // return value.
+ let sp = self.sess.source_map().start_point(self.token.span);
+ self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
+ false
+ }
+ (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
+ (true, Some(_)) => {
+ self.error_found_expr_would_be_stmt(lhs);
+ true
+ }
+ }
+ }
+
+ /// We've found an expression that would be parsed as a statement,
+ /// but the next token implies this should be parsed as an expression.
+ /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
+ fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
+ let mut err = self.struct_span_err(
+ self.token.span,
+ &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
+ );
+ err.span_label(self.token.span, "expected expression");
+ self.sess.expr_parentheses_needed(&mut err, lhs.span);
+ err.emit();
+ }
+
+ /// Possibly translate the current token to an associative operator.
+ /// The method does not advance the current token.
+ ///
+ /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
+ fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
+ let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
+ // When parsing const expressions, stop parsing when encountering `>`.
+ (
+ Some(
+ AssocOp::ShiftRight
+ | AssocOp::Greater
+ | AssocOp::GreaterEqual
+ | AssocOp::AssignOp(token::BinOpToken::Shr),
+ ),
+ _,
+ ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
+ return None;
+ }
+ (Some(op), _) => (op, self.token.span),
+ (None, Some((Ident { name: sym::and, span }, false))) => {
+ self.error_bad_logical_op("and", "&&", "conjunction");
+ (AssocOp::LAnd, span)
+ }
+ (None, Some((Ident { name: sym::or, span }, false))) => {
+ self.error_bad_logical_op("or", "||", "disjunction");
+ (AssocOp::LOr, span)
+ }
+ _ => return None,
+ };
+ Some(source_map::respan(span, op))
+ }
+
+ /// Error on `and` and `or` suggesting `&&` and `||` respectively.
+ fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
+ self.struct_span_err(self.token.span, &format!("`{bad}` is not a logical operator"))
+ .span_suggestion_short(
+ self.token.span,
+ &format!("use `{good}` to perform logical {english}"),
+ good,
+ Applicability::MachineApplicable,
+ )
+ .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
+ .emit();
+ }
+
+ /// Checks if this expression is a successfully parsed statement.
+ fn expr_is_complete(&self, e: &Expr) -> bool {
+ self.restrictions.contains(Restrictions::STMT_EXPR)
+ && !classify::expr_requires_semi_to_be_stmt(e)
+ }
+
+ /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
+ /// The other two variants are handled in `parse_prefix_range_expr` below.
+ fn parse_range_expr(
+ &mut self,
+ prec: usize,
+ lhs: P<Expr>,
+ op: AssocOp,
+ cur_op_span: Span,
+ ) -> PResult<'a, P<Expr>> {
+ let rhs = if self.is_at_start_of_range_notation_rhs() {
+ Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
+ } else {
+ None
+ };
+ let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
+ let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
+ let limits =
+ if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
+ let range = self.mk_range(Some(lhs), rhs, limits);
+ Ok(self.mk_expr(span, range, AttrVec::new()))
+ }
+
+ fn is_at_start_of_range_notation_rhs(&self) -> bool {
+ if self.token.can_begin_expr() {
+ // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
+ if self.token == token::OpenDelim(Delimiter::Brace) {
+ return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+ }
+ true
+ } else {
+ false
+ }
+ }
+
+ /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
+ fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
+ // Check for deprecated `...` syntax.
+ if self.token == token::DotDotDot {
+ self.err_dotdotdot_syntax(self.token.span);
+ }
+
+ debug_assert!(
+ [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
+ "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
+ self.token
+ );
+
+ let limits = match self.token.kind {
+ token::DotDot => RangeLimits::HalfOpen,
+ _ => RangeLimits::Closed,
+ };
+ let op = AssocOp::from_token(&self.token);
+ // FIXME: `parse_prefix_range_expr` is called when the current
+ // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
+ // parsed attributes, then trying to parse them here will always fail.
+ // We should figure out how we want attributes on range expressions to work.
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ self.collect_tokens_for_expr(attrs, |this, attrs| {
+ let lo = this.token.span;
+ this.bump();
+ let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
+ // RHS must be parsed with more associativity than the dots.
+ this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
+ .map(|x| (lo.to(x.span), Some(x)))?
+ } else {
+ (lo, None)
+ };
+ let range = this.mk_range(None, opt_end, limits);
+ Ok(this.mk_expr(span, range, attrs.into()))
+ })
+ }
+
+ /// Parses a prefix-unary-operator expr.
+ fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ let lo = self.token.span;
+
+ macro_rules! make_it {
+ ($this:ident, $attrs:expr, |this, _| $body:expr) => {
+ $this.collect_tokens_for_expr($attrs, |$this, attrs| {
+ let (hi, ex) = $body?;
+ Ok($this.mk_expr(lo.to(hi), ex, attrs.into()))
+ })
+ };
+ }
+
+ let this = self;
+
+ // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
+ match this.token.uninterpolate().kind {
+ token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
+ token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
+ token::BinOp(token::Minus) => {
+ make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
+ } // `-expr`
+ token::BinOp(token::Star) => {
+ make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
+ } // `*expr`
+ token::BinOp(token::And) | token::AndAnd => {
+ make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
+ }
+ token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
+ let mut err = this.struct_span_err(lo, "leading `+` is not supported");
+ err.span_label(lo, "unexpected `+`");
+
+ // a block on the LHS might have been intended to be an expression instead
+ if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
+ this.sess.expr_parentheses_needed(&mut err, *sp);
+ } else {
+ err.span_suggestion_verbose(
+ lo,
+ "try removing the `+`",
+ "",
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+
+ this.bump();
+ this.parse_prefix_expr(None)
+ } // `+expr`
+ // Recover from `++x`:
+ token::BinOp(token::Plus)
+ if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
+ {
+ let prev_is_semi = this.prev_token == token::Semi;
+ let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
+ // Eat both `+`s.
+ this.bump();
+ this.bump();
+
+ let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
+ this.recover_from_prefix_increment(operand_expr, pre_span, prev_is_semi)
+ }
+ token::Ident(..) if this.token.is_keyword(kw::Box) => {
+ make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
+ }
+ token::Ident(..) if this.is_mistaken_not_ident_negation() => {
+ make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
+ }
+ _ => return this.parse_dot_or_call_expr(Some(attrs)),
+ }
+ }
+
+ fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
+ self.bump();
+ let expr = self.parse_prefix_expr(None);
+ let (span, expr) = self.interpolated_or_expr_span(expr)?;
+ Ok((lo.to(span), expr))
+ }
+
+ fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
+ let (span, expr) = self.parse_prefix_expr_common(lo)?;
+ Ok((span, self.mk_unary(op, expr)))
+ }
+
+ // Recover on `!` suggesting for bitwise negation instead.
+ fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ self.struct_span_err(lo, "`~` cannot be used as a unary operator")
+ .span_suggestion_short(
+ lo,
+ "use `!` to perform bitwise not",
+ "!",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ self.parse_unary_expr(lo, UnOp::Not)
+ }
+
+ /// Parse `box expr`.
+ fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ let (span, expr) = self.parse_prefix_expr_common(lo)?;
+ self.sess.gated_spans.gate(sym::box_syntax, span);
+ Ok((span, ExprKind::Box(expr)))
+ }
+
+ fn is_mistaken_not_ident_negation(&self) -> bool {
+ let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
+ // These tokens can start an expression after `!`, but
+ // can't continue an expression after an ident
+ token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
+ token::Literal(..) | token::Pound => true,
+ _ => t.is_whole_expr(),
+ };
+ self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
+ }
+
+ /// Recover on `not expr` in favor of `!expr`.
+ fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ // Emit the error...
+ let not_token = self.look_ahead(1, |t| t.clone());
+ self.struct_span_err(
+ not_token.span,
+ &format!("unexpected {} after identifier", super::token_descr(&not_token)),
+ )
+ .span_suggestion_short(
+ // Span the `not` plus trailing whitespace to avoid
+ // trailing whitespace after the `!` in our suggestion
+ self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
+ "use `!` to perform logical negation",
+ "!",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ // ...and recover!
+ self.parse_unary_expr(lo, UnOp::Not)
+ }
+
+ /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
+ fn interpolated_or_expr_span(
+ &self,
+ expr: PResult<'a, P<Expr>>,
+ ) -> PResult<'a, (Span, P<Expr>)> {
+ expr.map(|e| {
+ (
+ match self.prev_token.kind {
+ TokenKind::Interpolated(..) => self.prev_token.span,
+ _ => e.span,
+ },
+ e,
+ )
+ })
+ }
+
+ fn parse_assoc_op_cast(
+ &mut self,
+ lhs: P<Expr>,
+ lhs_span: Span,
+ expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
+ ) -> PResult<'a, P<Expr>> {
+ let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
+ this.mk_expr(
+ this.mk_expr_sp(&lhs, lhs_span, rhs.span),
+ expr_kind(lhs, rhs),
+ AttrVec::new(),
+ )
+ };
+
+ // Save the state of the parser before parsing type normally, in case there is a
+ // LessThan comparison after this cast.
+ let parser_snapshot_before_type = self.clone();
+ let cast_expr = match self.parse_as_cast_ty() {
+ Ok(rhs) => mk_expr(self, lhs, rhs),
+ Err(type_err) => {
+ // Rewind to before attempting to parse the type with generics, to recover
+ // from situations like `x as usize < y` in which we first tried to parse
+ // `usize < y` as a type with generic arguments.
+ let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
+
+ // Check for typo of `'a: loop { break 'a }` with a missing `'`.
+ match (&lhs.kind, &self.token.kind) {
+ (
+ // `foo: `
+ ExprKind::Path(None, ast::Path { segments, .. }),
+ TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
+ ) if segments.len() == 1 => {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ let label = Label {
+ ident: Ident::from_str_and_span(
+ &format!("'{}", segments[0].ident),
+ segments[0].ident.span,
+ ),
+ };
+ match self.parse_labeled_expr(label, AttrVec::new(), false) {
+ Ok(expr) => {
+ type_err.cancel();
+ self.struct_span_err(label.ident.span, "malformed loop label")
+ .span_suggestion(
+ label.ident.span,
+ "use the correct loop label format",
+ label.ident,
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ return Ok(expr);
+ }
+ Err(err) => {
+ err.cancel();
+ self.restore_snapshot(snapshot);
+ }
+ }
+ }
+ _ => {}
+ }
+
+ match self.parse_path(PathStyle::Expr) {
+ Ok(path) => {
+ let (op_noun, op_verb) = match self.token.kind {
+ token::Lt => ("comparison", "comparing"),
+ token::BinOp(token::Shl) => ("shift", "shifting"),
+ _ => {
+ // We can end up here even without `<` being the next token, for
+ // example because `parse_ty_no_plus` returns `Err` on keywords,
+ // but `parse_path` returns `Ok` on them due to error recovery.
+ // Return original error and parser state.
+ *self = parser_snapshot_after_type;
+ return Err(type_err);
+ }
+ };
+
+ // Successfully parsed the type path leaving a `<` yet to parse.
+ type_err.cancel();
+
+ // Report non-fatal diagnostics, keep `x as usize` as an expression
+ // in AST and continue parsing.
+ let msg = format!(
+ "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
+ pprust::path_to_string(&path),
+ op_noun,
+ );
+ let span_after_type = parser_snapshot_after_type.token.span;
+ let expr =
+ mk_expr(self, lhs, self.mk_ty(path.span, TyKind::Path(None, path)));
+
+ self.struct_span_err(self.token.span, &msg)
+ .span_label(
+ self.look_ahead(1, |t| t.span).to(span_after_type),
+ "interpreted as generic arguments",
+ )
+ .span_label(self.token.span, format!("not interpreted as {op_noun}"))
+ .multipart_suggestion(
+ &format!("try {op_verb} the cast value"),
+ vec![
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ expr
+ }
+ Err(path_err) => {
+ // Couldn't parse as a path, return original error and parser state.
+ path_err.cancel();
+ *self = parser_snapshot_after_type;
+ return Err(type_err);
+ }
+ }
+ }
+ };
+
+ self.parse_and_disallow_postfix_after_cast(cast_expr)
+ }
+
+ /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
+ /// then emits an error and returns the newly parsed tree.
+ /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
+ fn parse_and_disallow_postfix_after_cast(
+ &mut self,
+ cast_expr: P<Expr>,
+ ) -> PResult<'a, P<Expr>> {
+ let span = cast_expr.span;
+ let (cast_kind, maybe_ascription_span) =
+ if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
+ ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
+ } else {
+ ("cast", None)
+ };
+
+ // Save the memory location of expr before parsing any following postfix operators.
+ // This will be compared with the memory location of the output expression.
+ // If they different we can assume we parsed another expression because the existing expression is not reallocated.
+ let addr_before = &*cast_expr as *const _ as usize;
+ let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
+ let changed = addr_before != &*with_postfix as *const _ as usize;
+
+ // Check if an illegal postfix operator has been added after the cast.
+ // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
+ if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
+ let msg = format!(
+ "{cast_kind} cannot be followed by {}",
+ match with_postfix.kind {
+ ExprKind::Index(_, _) => "indexing",
+ ExprKind::Try(_) => "`?`",
+ ExprKind::Field(_, _) => "a field access",
+ ExprKind::MethodCall(_, _, _) => "a method call",
+ ExprKind::Call(_, _) => "a function call",
+ ExprKind::Await(_) => "`.await`",
+ ExprKind::Err => return Ok(with_postfix),
+ _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
+ }
+ );
+ let mut err = self.struct_span_err(span, &msg);
+
+ let suggest_parens = |err: &mut DiagnosticBuilder<'_, _>| {
+ let suggestions = vec![
+ (span.shrink_to_lo(), "(".to_string()),
+ (span.shrink_to_hi(), ")".to_string()),
+ ];
+ err.multipart_suggestion(
+ "try surrounding the expression in parentheses",
+ suggestions,
+ Applicability::MachineApplicable,
+ );
+ };
+
+ // If type ascription is "likely an error", the user will already be getting a useful
+ // help message, and doesn't need a second.
+ if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
+ self.maybe_annotate_with_ascription(&mut err, false);
+ } else if let Some(ascription_span) = maybe_ascription_span {
+ let is_nightly = self.sess.unstable_features.is_nightly_build();
+ if is_nightly {
+ suggest_parens(&mut err);
+ }
+ err.span_suggestion(
+ ascription_span,
+ &format!(
+ "{}remove the type ascription",
+ if is_nightly { "alternatively, " } else { "" }
+ ),
+ "",
+ if is_nightly {
+ Applicability::MaybeIncorrect
+ } else {
+ Applicability::MachineApplicable
+ },
+ );
+ } else {
+ suggest_parens(&mut err);
+ }
+ err.emit();
+ };
+ Ok(with_postfix)
+ }
+
+ fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
+ let maybe_path = self.could_ascription_be_path(&lhs.kind);
+ self.last_type_ascription = Some((self.prev_token.span, maybe_path));
+ let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
+ self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
+ Ok(lhs)
+ }
+
+ /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
+ fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ self.expect_and()?;
+ let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
+ let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
+ let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
+ let expr = self.parse_prefix_expr(None);
+ let (hi, expr) = self.interpolated_or_expr_span(expr)?;
+ let span = lo.to(hi);
+ if let Some(lt) = lifetime {
+ self.error_remove_borrow_lifetime(span, lt.ident.span);
+ }
+ Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
+ }
+
+ fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
+ self.struct_span_err(span, "borrow expressions cannot be annotated with lifetimes")
+ .span_label(lt_span, "annotated with lifetime here")
+ .span_suggestion(
+ lt_span,
+ "remove the lifetime annotation",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ /// Parse `mut?` or `raw [ const | mut ]`.
+ fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
+ if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
+ // `raw [ const | mut ]`.
+ let found_raw = self.eat_keyword(kw::Raw);
+ assert!(found_raw);
+ let mutability = self.parse_const_or_mut().unwrap();
+ self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
+ (ast::BorrowKind::Raw, mutability)
+ } else {
+ // `mut?`
+ (ast::BorrowKind::Ref, self.parse_mutability())
+ }
+ }
+
+ /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
+ fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ self.collect_tokens_for_expr(attrs, |this, attrs| {
+ let base = this.parse_bottom_expr();
+ let (span, base) = this.interpolated_or_expr_span(base)?;
+ this.parse_dot_or_call_expr_with(base, span, attrs)
+ })
+ }
+
+ pub(super) fn parse_dot_or_call_expr_with(
+ &mut self,
+ e0: P<Expr>,
+ lo: Span,
+ mut attrs: Vec<ast::Attribute>,
+ ) -> PResult<'a, P<Expr>> {
+ // Stitch the list of outer attributes onto the return value.
+ // A little bit ugly, but the best way given the current code
+ // structure
+ self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
+ expr.map(|mut expr| {
+ attrs.extend::<Vec<_>>(expr.attrs.into());
+ expr.attrs = attrs.into();
+ expr
+ })
+ })
+ }
+
+ fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+ loop {
+ let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
+ // we are using noexpect here because we don't expect a `?` directly after a `return`
+ // which could be suggested otherwise
+ self.eat_noexpect(&token::Question)
+ } else {
+ self.eat(&token::Question)
+ };
+ if has_question {
+ // `expr?`
+ e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e), AttrVec::new());
+ continue;
+ }
+ let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
+ // we are using noexpect here because we don't expect a `.` directly after a `return`
+ // which could be suggested otherwise
+ self.eat_noexpect(&token::Dot)
+ } else {
+ self.eat(&token::Dot)
+ };
+ if has_dot {
+ // expr.f
+ e = self.parse_dot_suffix_expr(lo, e)?;
+ continue;
+ }
+ if self.expr_is_complete(&e) {
+ return Ok(e);
+ }
+ e = match self.token.kind {
+ token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
+ token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
+ _ => return Ok(e),
+ }
+ }
+ }
+
+ fn look_ahead_type_ascription_as_field(&mut self) -> bool {
+ self.look_ahead(1, |t| t.is_ident())
+ && self.look_ahead(2, |t| t == &token::Colon)
+ && self.look_ahead(3, |t| t.can_begin_expr())
+ }
+
+ fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+ match self.token.uninterpolate().kind {
+ token::Ident(..) => self.parse_dot_suffix(base, lo),
+ token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
+ Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
+ }
+ token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
+ Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
+ }
+ _ => {
+ self.error_unexpected_after_dot();
+ Ok(base)
+ }
+ }
+ }
+
+ fn error_unexpected_after_dot(&self) {
+ // FIXME Could factor this out into non_fatal_unexpected or something.
+ let actual = pprust::token_to_string(&self.token);
+ self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
+ }
+
+ // We need an identifier or integer, but the next token is a float.
+ // Break the float into components to extract the identifier or integer.
+ // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
+ // parts unless those parts are processed immediately. `TokenCursor` should either
+ // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
+ // we should break everything including floats into more basic proc-macro style
+ // tokens in the lexer (probably preferable).
+ fn parse_tuple_field_access_expr_float(
+ &mut self,
+ lo: Span,
+ base: P<Expr>,
+ float: Symbol,
+ suffix: Option<Symbol>,
+ ) -> P<Expr> {
+ #[derive(Debug)]
+ enum FloatComponent {
+ IdentLike(String),
+ Punct(char),
+ }
+ use FloatComponent::*;
+
+ let float_str = float.as_str();
+ let mut components = Vec::new();
+ let mut ident_like = String::new();
+ for c in float_str.chars() {
+ if c == '_' || c.is_ascii_alphanumeric() {
+ ident_like.push(c);
+ } else if matches!(c, '.' | '+' | '-') {
+ if !ident_like.is_empty() {
+ components.push(IdentLike(mem::take(&mut ident_like)));
+ }
+ components.push(Punct(c));
+ } else {
+ panic!("unexpected character in a float token: {:?}", c)
+ }
+ }
+ if !ident_like.is_empty() {
+ components.push(IdentLike(ident_like));
+ }
+
+ // With proc macros the span can refer to anything, the source may be too short,
+ // or too long, or non-ASCII. It only makes sense to break our span into components
+ // if its underlying text is identical to our float literal.
+ let span = self.token.span;
+ let can_take_span_apart =
+ || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
+
+ match &*components {
+ // 1e2
+ [IdentLike(i)] => {
+ self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
+ }
+ // 1.
+ [IdentLike(i), Punct('.')] => {
+ let (ident_span, dot_span) = if can_take_span_apart() {
+ let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
+ let ident_span = span.with_hi(span.lo + ident_len);
+ let dot_span = span.with_lo(span.lo + ident_len);
+ (ident_span, dot_span)
+ } else {
+ (span, span)
+ };
+ assert!(suffix.is_none());
+ let symbol = Symbol::intern(&i);
+ self.token = Token::new(token::Ident(symbol, false), ident_span);
+ let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
+ self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
+ }
+ // 1.2 | 1.2e3
+ [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
+ let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
+ let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
+ let ident1_span = span.with_hi(span.lo + ident1_len);
+ let dot_span = span
+ .with_lo(span.lo + ident1_len)
+ .with_hi(span.lo + ident1_len + BytePos(1));
+ let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
+ (ident1_span, dot_span, ident2_span)
+ } else {
+ (span, span, span)
+ };
+ let symbol1 = Symbol::intern(&i1);
+ self.token = Token::new(token::Ident(symbol1, false), ident1_span);
+ // This needs to be `Spacing::Alone` to prevent regressions.
+ // See issue #76399 and PR #76285 for more details
+ let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
+ let base1 =
+ self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
+ let symbol2 = Symbol::intern(&i2);
+ let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
+ self.bump_with((next_token2, self.token_spacing)); // `.`
+ self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
+ }
+ // 1e+ | 1e- (recovered)
+ [IdentLike(_), Punct('+' | '-')] |
+ // 1e+2 | 1e-2
+ [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
+ // 1.2e+ | 1.2e-
+ [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
+ // 1.2e+3 | 1.2e-3
+ [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
+ // See the FIXME about `TokenCursor` above.
+ self.error_unexpected_after_dot();
+ base
+ }
+ _ => panic!("unexpected components in a float token: {:?}", components),
+ }
+ }
+
+ fn parse_tuple_field_access_expr(
+ &mut self,
+ lo: Span,
+ base: P<Expr>,
+ field: Symbol,
+ suffix: Option<Symbol>,
+ next_token: Option<(Token, Spacing)>,
+ ) -> P<Expr> {
+ match next_token {
+ Some(next_token) => self.bump_with(next_token),
+ None => self.bump(),
+ }
+ let span = self.prev_token.span;
+ let field = ExprKind::Field(base, Ident::new(field, span));
+ self.expect_no_suffix(span, "a tuple index", suffix);
+ self.mk_expr(lo.to(span), field, AttrVec::new())
+ }
+
+ /// Parse a function call expression, `expr(...)`.
+ fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
+ let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
+ && self.look_ahead_type_ascription_as_field()
+ {
+ Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
+ } else {
+ None
+ };
+ let open_paren = self.token.span;
+
+ let mut seq = self.parse_paren_expr_seq().map(|args| {
+ self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args), AttrVec::new())
+ });
+ if let Some(expr) =
+ self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
+ {
+ return expr;
+ }
+ self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
+ }
+
+ /// If we encounter a parser state that looks like the user has written a `struct` literal with
+ /// parentheses instead of braces, recover the parser state and provide suggestions.
+ #[instrument(skip(self, seq, snapshot), level = "trace")]
+ fn maybe_recover_struct_lit_bad_delims(
+ &mut self,
+ lo: Span,
+ open_paren: Span,
+ seq: &mut PResult<'a, P<Expr>>,
+ snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
+ ) -> Option<P<Expr>> {
+ match (seq.as_mut(), snapshot) {
+ (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
+ let name = pprust::path_to_string(&path);
+ snapshot.bump(); // `(`
+ match snapshot.parse_struct_fields(path, false, Delimiter::Parenthesis) {
+ Ok((fields, ..))
+ if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
+ {
+ // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
+ // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
+ self.restore_snapshot(snapshot);
+ let close_paren = self.prev_token.span;
+ let span = lo.to(self.prev_token.span);
+ if !fields.is_empty() {
+ let replacement_err = self.struct_span_err(
+ span,
+ "invalid `struct` delimiters or `fn` call arguments",
+ );
+ mem::replace(err, replacement_err).cancel();
+
+ err.multipart_suggestion(
+ &format!("if `{name}` is a struct, use braces as delimiters"),
+ vec![
+ (open_paren, " { ".to_string()),
+ (close_paren, " }".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ err.multipart_suggestion(
+ &format!("if `{name}` is a function, use the arguments directly"),
+ fields
+ .into_iter()
+ .map(|field| (field.span.until(field.expr.span), String::new()))
+ .collect(),
+ Applicability::MaybeIncorrect,
+ );
+ err.emit();
+ } else {
+ err.emit();
+ }
+ return Some(self.mk_expr_err(span));
+ }
+ Ok(_) => {}
+ Err(mut err) => {
+ err.emit();
+ }
+ }
+ }
+ _ => {}
+ }
+ None
+ }
+
+ /// Parse an indexing expression `expr[...]`.
+ fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+ self.bump(); // `[`
+ let index = self.parse_expr()?;
+ self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+ Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index), AttrVec::new()))
+ }
+
+ /// Assuming we have just parsed `.`, continue parsing into an expression.
+ fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+ if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
+ return Ok(self.mk_await_expr(self_arg, lo));
+ }
+
+ let fn_span_lo = self.token.span;
+ let mut segment = self.parse_path_segment(PathStyle::Expr, None)?;
+ self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(Delimiter::Parenthesis)]);
+ self.check_turbofish_missing_angle_brackets(&mut segment);
+
+ if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ // Method call `expr.f()`
+ let mut args = self.parse_paren_expr_seq()?;
+ args.insert(0, self_arg);
+
+ let fn_span = fn_span_lo.to(self.prev_token.span);
+ let span = lo.to(self.prev_token.span);
+ Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args, fn_span), AttrVec::new()))
+ } else {
+ // Field access `expr.f`
+ if let Some(args) = segment.args {
+ self.struct_span_err(
+ args.span(),
+ "field expressions cannot have generic arguments",
+ )
+ .emit();
+ }
+
+ let span = lo.to(self.prev_token.span);
+ Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
+ }
+ }
+
+ /// At the bottom (top?) of the precedence hierarchy,
+ /// Parses things like parenthesized exprs, macros, `return`, etc.
+ ///
+ /// N.B., this does not parse outer attributes, and is private because it only works
+ /// correctly if called from `parse_dot_or_call_expr()`.
+ fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
+ maybe_recover_from_interpolated_ty_qpath!(self, true);
+ maybe_whole_expr!(self);
+
+ // Outer attributes are already parsed and will be
+ // added to the return value after the fact.
+ //
+ // Therefore, prevent sub-parser from parsing
+ // attributes by giving them an empty "already-parsed" list.
+ let attrs = AttrVec::new();
+
+ // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
+ let lo = self.token.span;
+ if let token::Literal(_) = self.token.kind {
+ // This match arm is a special-case of the `_` match arm below and
+ // could be removed without changing functionality, but it's faster
+ // to have it here, especially for programs with large constants.
+ self.parse_lit_expr(attrs)
+ } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ self.parse_tuple_parens_expr(attrs)
+ } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
+ self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
+ } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
+ self.parse_closure_expr(attrs).map_err(|mut err| {
+ // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
+ // then suggest parens around the lhs.
+ if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
+ self.sess.expr_parentheses_needed(&mut err, *sp);
+ }
+ err
+ })
+ } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
+ self.parse_array_or_repeat_expr(attrs, Delimiter::Bracket)
+ } else if self.check_path() {
+ self.parse_path_start_expr(attrs)
+ } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
+ self.parse_closure_expr(attrs)
+ } else if self.eat_keyword(kw::If) {
+ self.parse_if_expr(attrs)
+ } else if self.check_keyword(kw::For) {
+ if self.choose_generics_over_qpath(1) {
+ self.parse_closure_expr(attrs)
+ } else {
+ assert!(self.eat_keyword(kw::For));
+ self.parse_for_expr(None, self.prev_token.span, attrs)
+ }
+ } else if self.eat_keyword(kw::While) {
+ self.parse_while_expr(None, self.prev_token.span, attrs)
+ } else if let Some(label) = self.eat_label() {
+ self.parse_labeled_expr(label, attrs, true)
+ } else if self.eat_keyword(kw::Loop) {
+ let sp = self.prev_token.span;
+ self.parse_loop_expr(None, self.prev_token.span, attrs).map_err(|mut err| {
+ err.span_label(sp, "while parsing this `loop` expression");
+ err
+ })
+ } else if self.eat_keyword(kw::Continue) {
+ let kind = ExprKind::Continue(self.eat_label());
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ } else if self.eat_keyword(kw::Match) {
+ let match_sp = self.prev_token.span;
+ self.parse_match_expr(attrs).map_err(|mut err| {
+ err.span_label(match_sp, "while parsing this `match` expression");
+ err
+ })
+ } else if self.eat_keyword(kw::Unsafe) {
+ let sp = self.prev_token.span;
+ self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
+ .map_err(|mut err| {
+ err.span_label(sp, "while parsing this `unsafe` expression");
+ err
+ })
+ } else if self.check_inline_const(0) {
+ self.parse_const_block(lo.to(self.token.span), false)
+ } else if self.is_do_catch_block() {
+ self.recover_do_catch(attrs)
+ } else if self.is_try_block() {
+ self.expect_keyword(kw::Try)?;
+ self.parse_try_block(lo, attrs)
+ } else if self.eat_keyword(kw::Return) {
+ self.parse_return_expr(attrs)
+ } else if self.eat_keyword(kw::Break) {
+ self.parse_break_expr(attrs)
+ } else if self.eat_keyword(kw::Yield) {
+ self.parse_yield_expr(attrs)
+ } else if self.is_do_yeet() {
+ self.parse_yeet_expr(attrs)
+ } else if self.check_keyword(kw::Let) {
+ self.parse_let_expr(attrs)
+ } else if self.eat_keyword(kw::Underscore) {
+ Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore, attrs))
+ } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
+ // Don't complain about bare semicolons after unclosed braces
+ // recovery in order to keep the error count down. Fixing the
+ // delimiters will possibly also fix the bare semicolon found in
+ // expression context. For example, silence the following error:
+ //
+ // error: expected expression, found `;`
+ // --> file.rs:2:13
+ // |
+ // 2 | foo(bar(;
+ // | ^ expected expression
+ self.bump();
+ Ok(self.mk_expr_err(self.token.span))
+ } else if self.token.uninterpolated_span().rust_2018() {
+ // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
+ if self.check_keyword(kw::Async) {
+ if self.is_async_block() {
+ // Check for `async {` and `async move {`.
+ self.parse_async_block(attrs)
+ } else {
+ self.parse_closure_expr(attrs)
+ }
+ } else if self.eat_keyword(kw::Await) {
+ self.recover_incorrect_await_syntax(lo, self.prev_token.span, attrs)
+ } else {
+ self.parse_lit_expr(attrs)
+ }
+ } else {
+ self.parse_lit_expr(attrs)
+ }
+ }
+
+ fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ match self.parse_opt_lit() {
+ Some(literal) => {
+ let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal), attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+ None => self.try_macro_suggestion(),
+ }
+ }
+
+ fn parse_tuple_parens_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+ let (es, trailing_comma) = match self.parse_seq_to_end(
+ &token::CloseDelim(Delimiter::Parenthesis),
+ SeqSep::trailing_allowed(token::Comma),
+ |p| p.parse_expr_catch_underscore(),
+ ) {
+ Ok(x) => x,
+ Err(err) => {
+ return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, Err(err)));
+ }
+ };
+ let kind = if es.len() == 1 && !trailing_comma {
+ // `(e)` is parenthesized `e`.
+ ExprKind::Paren(es.into_iter().next().unwrap())
+ } else {
+ // `(e,)` is a tuple with only one field, `e`.
+ ExprKind::Tup(es)
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ fn parse_array_or_repeat_expr(
+ &mut self,
+ attrs: AttrVec,
+ close_delim: Delimiter,
+ ) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.bump(); // `[` or other open delim
+
+ let close = &token::CloseDelim(close_delim);
+ let kind = if self.eat(close) {
+ // Empty vector
+ ExprKind::Array(Vec::new())
+ } else {
+ // Non-empty vector
+ let first_expr = self.parse_expr()?;
+ if self.eat(&token::Semi) {
+ // Repeating array syntax: `[ 0; 512 ]`
+ let count = self.parse_anon_const_expr()?;
+ self.expect(close)?;
+ ExprKind::Repeat(first_expr, count)
+ } else if self.eat(&token::Comma) {
+ // Vector with two or more elements.
+ let sep = SeqSep::trailing_allowed(token::Comma);
+ let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
+ let mut exprs = vec![first_expr];
+ exprs.extend(remaining_exprs);
+ ExprKind::Array(exprs)
+ } else {
+ // Vector with one element
+ self.expect(close)?;
+ ExprKind::Array(vec![first_expr])
+ }
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ 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 lo = path.span;
+
+ // `!`, as an operator, is prefix, so we know this isn't that.
+ let (hi, kind) = if self.eat(&token::Not) {
+ // MACRO INVOCATION expression
+ if qself.is_some() {
+ self.struct_span_err(path.span, "macros cannot use qualified paths").emit();
+ }
+ let mac = MacCall {
+ path,
+ args: self.parse_mac_args()?,
+ prior_type_ascription: self.last_type_ascription,
+ };
+ (self.prev_token.span, ExprKind::MacCall(mac))
+ } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
+ if let Some(expr) = self.maybe_parse_struct_expr(qself.as_ref(), &path, &attrs) {
+ if qself.is_some() {
+ self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
+ }
+ return expr;
+ } else {
+ (path.span, ExprKind::Path(qself, path))
+ }
+ } else {
+ (path.span, ExprKind::Path(qself, path))
+ };
+
+ let expr = self.mk_expr(lo.to(hi), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ /// Parse `'label: $expr`. The label is already parsed.
+ fn parse_labeled_expr(
+ &mut self,
+ label: Label,
+ attrs: AttrVec,
+ mut consume_colon: bool,
+ ) -> PResult<'a, P<Expr>> {
+ let lo = label.ident.span;
+ let label = Some(label);
+ let ate_colon = self.eat(&token::Colon);
+ let expr = if self.eat_keyword(kw::While) {
+ self.parse_while_expr(label, lo, attrs)
+ } else if self.eat_keyword(kw::For) {
+ self.parse_for_expr(label, lo, attrs)
+ } else if self.eat_keyword(kw::Loop) {
+ self.parse_loop_expr(label, lo, attrs)
+ } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
+ || self.token.is_whole_block()
+ {
+ self.parse_block_expr(label, lo, BlockCheckMode::Default, attrs)
+ } else if !ate_colon
+ && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
+ {
+ // We're probably inside of a `Path<'a>` that needs a turbofish
+ let msg = "expected `while`, `for`, `loop` or `{` after a label";
+ self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
+ consume_colon = false;
+ Ok(self.mk_expr_err(lo))
+ } else {
+ let msg = "expected `while`, `for`, `loop` or `{` after a label";
+
+ let mut err = self.struct_span_err(self.token.span, msg);
+ err.span_label(self.token.span, msg);
+
+ // Continue as an expression in an effort to recover on `'label: non_block_expr`.
+ let expr = self.parse_expr().map(|expr| {
+ let span = expr.span;
+
+ let found_labeled_breaks = {
+ struct FindLabeledBreaksVisitor(bool);
+
+ impl<'ast> Visitor<'ast> for FindLabeledBreaksVisitor {
+ fn visit_expr_post(&mut self, ex: &'ast Expr) {
+ if let ExprKind::Break(Some(_label), _) = ex.kind {
+ self.0 = true;
+ }
+ }
+ }
+
+ let mut vis = FindLabeledBreaksVisitor(false);
+ vis.visit_expr(&expr);
+ vis.0
+ };
+
+ // Suggestion involves adding a (as of time of writing this, unstable) labeled block.
+ //
+ // If there are no breaks that may use this label, suggest removing the label and
+ // recover to the unmodified expression.
+ if !found_labeled_breaks {
+ let msg = "consider removing the label";
+ err.span_suggestion_verbose(
+ lo.until(span),
+ msg,
+ "",
+ Applicability::MachineApplicable,
+ );
+
+ return expr;
+ }
+
+ let sugg_msg = "consider enclosing expression in a block";
+ let suggestions = vec![
+ (span.shrink_to_lo(), "{ ".to_owned()),
+ (span.shrink_to_hi(), " }".to_owned()),
+ ];
+
+ err.multipart_suggestion_verbose(
+ sugg_msg,
+ suggestions,
+ Applicability::MachineApplicable,
+ );
+
+ // Replace `'label: non_block_expr` with `'label: {non_block_expr}` in order to supress future errors about `break 'label`.
+ let stmt = self.mk_stmt(span, StmtKind::Expr(expr));
+ let blk = self.mk_block(vec![stmt], BlockCheckMode::Default, span);
+ self.mk_expr(span, ExprKind::Block(blk, label), ThinVec::new())
+ });
+
+ err.emit();
+ expr
+ }?;
+
+ if !ate_colon && consume_colon {
+ self.error_labeled_expr_must_be_followed_by_colon(lo, expr.span);
+ }
+
+ Ok(expr)
+ }
+
+ fn error_labeled_expr_must_be_followed_by_colon(&self, lo: Span, span: Span) {
+ self.struct_span_err(span, "labeled expression must be followed by `:`")
+ .span_label(lo, "the label")
+ .span_suggestion_short(
+ lo.shrink_to_hi(),
+ "add `:` after the label",
+ ": ",
+ Applicability::MachineApplicable,
+ )
+ .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
+ .emit();
+ }
+
+ /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
+ fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+
+ self.bump(); // `do`
+ self.bump(); // `catch`
+
+ let span_dc = lo.to(self.prev_token.span);
+ self.struct_span_err(span_dc, "found removed `do catch` syntax")
+ .span_suggestion(
+ span_dc,
+ "replace with the new syntax",
+ "try",
+ Applicability::MachineApplicable,
+ )
+ .note("following RFC #2388, the new non-placeholder syntax is `try`")
+ .emit();
+
+ self.parse_try_block(lo, attrs)
+ }
+
+ /// Parse an expression if the token can begin one.
+ fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
+ Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
+ }
+
+ /// Parse `"return" expr?`.
+ fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let kind = ExprKind::Ret(self.parse_expr_opt()?);
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ /// Parse `"do" "yeet" expr?`.
+ fn parse_yeet_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+
+ self.bump(); // `do`
+ self.bump(); // `yeet`
+
+ let kind = ExprKind::Yeet(self.parse_expr_opt()?);
+
+ let span = lo.to(self.prev_token.span);
+ self.sess.gated_spans.gate(sym::yeet_expr, span);
+ let expr = self.mk_expr(span, kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
+ /// If the label is followed immediately by a `:` token, the label and `:` are
+ /// parsed as part of the expression (i.e. a labeled loop). The language team has
+ /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
+ /// the break expression of an unlabeled break is a labeled loop (as in
+ /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
+ /// expression only gets a warning for compatibility reasons; and a labeled break
+ /// with a labeled loop does not even get a warning because there is no ambiguity.
+ fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let mut label = self.eat_label();
+ let kind = if label.is_some() && self.token == token::Colon {
+ // The value expression can be a labeled loop, see issue #86948, e.g.:
+ // `loop { break 'label: loop { break 'label 42; }; }`
+ let lexpr = self.parse_labeled_expr(label.take().unwrap(), AttrVec::new(), true)?;
+ self.struct_span_err(
+ lexpr.span,
+ "parentheses are required around this expression to avoid confusion with a labeled break expression",
+ )
+ .multipart_suggestion(
+ "wrap the expression in parentheses",
+ vec![
+ (lexpr.span.shrink_to_lo(), "(".to_string()),
+ (lexpr.span.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ Some(lexpr)
+ } else if self.token != token::OpenDelim(Delimiter::Brace)
+ || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+ {
+ let expr = self.parse_expr_opt()?;
+ if let Some(ref expr) = expr {
+ if label.is_some()
+ && matches!(
+ expr.kind,
+ ExprKind::While(_, _, None)
+ | ExprKind::ForLoop(_, _, _, None)
+ | ExprKind::Loop(_, None)
+ | ExprKind::Block(_, None)
+ )
+ {
+ self.sess.buffer_lint_with_diagnostic(
+ BREAK_WITH_LABEL_AND_LOOP,
+ lo.to(expr.span),
+ ast::CRATE_NODE_ID,
+ "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
+ BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
+ );
+ }
+ }
+ expr
+ } else {
+ None
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind), attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ /// Parse `"yield" expr?`.
+ fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let kind = ExprKind::Yield(self.parse_expr_opt()?);
+ let span = lo.to(self.prev_token.span);
+ self.sess.gated_spans.gate(sym::generators, span);
+ let expr = self.mk_expr(span, kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr)
+ }
+
+ /// Returns a string literal if the next token is a string literal.
+ /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
+ /// and returns `None` if the next token is not literal at all.
+ pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
+ match self.parse_opt_lit() {
+ Some(lit) => match lit.kind {
+ ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
+ style,
+ symbol: lit.token.symbol,
+ suffix: lit.token.suffix,
+ span: lit.span,
+ symbol_unescaped,
+ }),
+ _ => Err(Some(lit)),
+ },
+ None => Err(None),
+ }
+ }
+
+ pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
+ self.parse_opt_lit().ok_or_else(|| {
+ if let token::Interpolated(inner) = &self.token.kind {
+ let expr = match inner.as_ref() {
+ token::NtExpr(expr) => Some(expr),
+ token::NtLiteral(expr) => Some(expr),
+ _ => None,
+ };
+ if let Some(expr) = expr {
+ if matches!(expr.kind, ExprKind::Err) {
+ let mut err = self
+ .diagnostic()
+ .struct_span_err(self.token.span, "invalid interpolated expression");
+ err.downgrade_to_delayed_bug();
+ return err;
+ }
+ }
+ }
+ let msg = format!("unexpected token: {}", super::token_descr(&self.token));
+ self.struct_span_err(self.token.span, &msg)
+ })
+ }
+
+ /// Matches `lit = true | false | token_lit`.
+ /// Returns `None` if the next token is not a literal.
+ pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
+ let mut recovered = None;
+ if self.token == token::Dot {
+ // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
+ // dot would follow an optional literal, so we do this unconditionally.
+ recovered = self.look_ahead(1, |next_token| {
+ if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
+ next_token.kind
+ {
+ if self.token.span.hi() == next_token.span.lo() {
+ let s = String::from("0.") + symbol.as_str();
+ let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
+ return Some(Token::new(kind, self.token.span.to(next_token.span)));
+ }
+ }
+ None
+ });
+ if let Some(token) = &recovered {
+ self.bump();
+ self.error_float_lits_must_have_int_part(&token);
+ }
+ }
+
+ let token = recovered.as_ref().unwrap_or(&self.token);
+ match Lit::from_token(token) {
+ Ok(lit) => {
+ self.bump();
+ Some(lit)
+ }
+ Err(LitError::NotLiteral) => None,
+ Err(err) => {
+ let span = token.span;
+ let token::Literal(lit) = token.kind else {
+ unreachable!();
+ };
+ self.bump();
+ self.report_lit_error(err, lit, span);
+ // Pack possible quotes and prefixes from the original literal into
+ // the error literal's symbol so they can be pretty-printed faithfully.
+ let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
+ let symbol = Symbol::intern(&suffixless_lit.to_string());
+ let lit = token::Lit::new(token::Err, symbol, lit.suffix);
+ Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
+ }
+ }
+ }
+
+ fn error_float_lits_must_have_int_part(&self, token: &Token) {
+ self.struct_span_err(token.span, "float literals must have an integer part")
+ .span_suggestion(
+ token.span,
+ "must have an integer part",
+ pprust::token_to_string(token),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
+ // Checks if `s` looks like i32 or u1234 etc.
+ fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
+ s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
+ }
+
+ // Try to lowercase the prefix if it's a valid base prefix.
+ fn fix_base_capitalisation(s: &str) -> Option<String> {
+ if let Some(stripped) = s.strip_prefix('B') {
+ Some(format!("0b{stripped}"))
+ } else if let Some(stripped) = s.strip_prefix('O') {
+ Some(format!("0o{stripped}"))
+ } else if let Some(stripped) = s.strip_prefix('X') {
+ Some(format!("0x{stripped}"))
+ } else {
+ None
+ }
+ }
+
+ let token::Lit { kind, suffix, .. } = lit;
+ match err {
+ // `NotLiteral` is not an error by itself, so we don't report
+ // it and give the parser opportunity to try something else.
+ LitError::NotLiteral => {}
+ // `LexerError` *is* an error, but it was already reported
+ // by lexer, so here we don't report it the second time.
+ LitError::LexerError => {}
+ LitError::InvalidSuffix => {
+ self.expect_no_suffix(
+ span,
+ &format!("{} {} literal", kind.article(), kind.descr()),
+ suffix,
+ );
+ }
+ LitError::InvalidIntSuffix => {
+ let suf = suffix.expect("suffix error with no suffix");
+ let suf = suf.as_str();
+ if looks_like_width_suffix(&['i', 'u'], &suf) {
+ // If it looks like a width, try to be helpful.
+ let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
+ self.struct_span_err(span, &msg)
+ .help("valid widths are 8, 16, 32, 64 and 128")
+ .emit();
+ } else if let Some(fixed) = fix_base_capitalisation(suf) {
+ let msg = "invalid base prefix for number literal";
+
+ self.struct_span_err(span, msg)
+ .note("base prefixes (`0xff`, `0b1010`, `0o755`) are lowercase")
+ .span_suggestion(
+ span,
+ "try making the prefix lowercase",
+ fixed,
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ } else {
+ let msg = format!("invalid suffix `{suf}` for number literal");
+ self.struct_span_err(span, &msg)
+ .span_label(span, format!("invalid suffix `{suf}`"))
+ .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
+ .emit();
+ }
+ }
+ LitError::InvalidFloatSuffix => {
+ let suf = suffix.expect("suffix error with no suffix");
+ let suf = suf.as_str();
+ if looks_like_width_suffix(&['f'], suf) {
+ // If it looks like a width, try to be helpful.
+ let msg = format!("invalid width `{}` for float literal", &suf[1..]);
+ self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
+ } else {
+ let msg = format!("invalid suffix `{suf}` for float literal");
+ self.struct_span_err(span, &msg)
+ .span_label(span, format!("invalid suffix `{suf}`"))
+ .help("valid suffixes are `f32` and `f64`")
+ .emit();
+ }
+ }
+ LitError::NonDecimalFloat(base) => {
+ let descr = match base {
+ 16 => "hexadecimal",
+ 8 => "octal",
+ 2 => "binary",
+ _ => unreachable!(),
+ };
+ self.struct_span_err(span, &format!("{descr} float literal is not supported"))
+ .span_label(span, "not supported")
+ .emit();
+ }
+ LitError::IntTooLarge => {
+ self.struct_span_err(span, "integer literal is too large").emit();
+ }
+ }
+ }
+
+ pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
+ if let Some(suf) = suffix {
+ let mut err = if kind == "a tuple index"
+ && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
+ {
+ // #59553: warn instead of reject out of hand to allow the fix to percolate
+ // through the ecosystem when people fix their macros
+ let mut err = self
+ .sess
+ .span_diagnostic
+ .struct_span_warn(sp, &format!("suffixes on {kind} are invalid"));
+ err.note(&format!(
+ "`{}` is *temporarily* accepted on tuple index fields as it was \
+ incorrectly accepted on stable for a few releases",
+ suf,
+ ));
+ err.help(
+ "on proc macros, you'll want to use `syn::Index::from` or \
+ `proc_macro::Literal::*_unsuffixed` for code that will desugar \
+ to tuple field access",
+ );
+ err.note(
+ "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
+ for more information",
+ );
+ err
+ } else {
+ self.struct_span_err(sp, &format!("suffixes on {kind} are invalid"))
+ .forget_guarantee()
+ };
+ err.span_label(sp, format!("invalid suffix `{suf}`"));
+ err.emit();
+ }
+ }
+
+ /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
+ /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
+ pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
+ maybe_whole_expr!(self);
+
+ let lo = self.token.span;
+ let minus_present = self.eat(&token::BinOp(token::Minus));
+ let lit = self.parse_lit()?;
+ let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
+
+ if minus_present {
+ Ok(self.mk_expr(
+ lo.to(self.prev_token.span),
+ self.mk_unary(UnOp::Neg, expr),
+ AttrVec::new(),
+ ))
+ } else {
+ Ok(expr)
+ }
+ }
+
+ fn is_array_like_block(&mut self) -> bool {
+ self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
+ && self.look_ahead(2, |t| t == &token::Comma)
+ && self.look_ahead(3, |t| t.can_begin_expr())
+ }
+
+ /// Emits a suggestion if it looks like the user meant an array but
+ /// accidentally used braces, causing the code to be interpreted as a block
+ /// expression.
+ fn maybe_suggest_brackets_instead_of_braces(
+ &mut self,
+ lo: Span,
+ attrs: AttrVec,
+ ) -> Option<P<Expr>> {
+ let mut snapshot = self.create_snapshot_for_diagnostic();
+ match snapshot.parse_array_or_repeat_expr(attrs, Delimiter::Brace) {
+ Ok(arr) => {
+ let hi = snapshot.prev_token.span;
+ self.struct_span_err(arr.span, "this is a block expression, not an array")
+ .multipart_suggestion(
+ "to make an array, use square brackets instead of curly braces",
+ vec![(lo, "[".to_owned()), (hi, "]".to_owned())],
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+
+ self.restore_snapshot(snapshot);
+ Some(self.mk_expr_err(arr.span))
+ }
+ Err(e) => {
+ e.cancel();
+ None
+ }
+ }
+ }
+
+ /// Parses a block or unsafe block.
+ pub(super) fn parse_block_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ blk_mode: BlockCheckMode,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ if self.is_array_like_block() {
+ if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo, attrs.clone()) {
+ return Ok(arr);
+ }
+ }
+
+ if let Some(label) = opt_label {
+ self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
+ }
+
+ if self.token.is_whole_block() {
+ self.struct_span_err(self.token.span, "cannot use a `block` macro fragment here")
+ .span_label(lo.to(self.token.span), "the `block` fragment is within this context")
+ .emit();
+ }
+
+ let (inner_attrs, blk) = self.parse_block_common(lo, blk_mode)?;
+ attrs.extend(inner_attrs);
+ Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
+ }
+
+ /// Parse a block which takes no attributes and has no label
+ fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
+ let blk = self.parse_block()?;
+ Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()))
+ }
+
+ /// Parses a closure expression (e.g., `move |args| expr`).
+ fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+
+ let binder = if self.check_keyword(kw::For) {
+ let lo = self.token.span;
+ let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+ let span = lo.to(self.prev_token.span);
+
+ self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
+
+ ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
+ } else {
+ ClosureBinder::NotPresent
+ };
+
+ let movability =
+ if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
+
+ let asyncness = if self.token.uninterpolated_span().rust_2018() {
+ self.parse_asyncness()
+ } else {
+ Async::No
+ };
+
+ let capture_clause = self.parse_capture_clause()?;
+ let decl = self.parse_fn_block_decl()?;
+ let decl_hi = self.prev_token.span;
+ let mut body = match decl.output {
+ FnRetTy::Default(_) => {
+ let restrictions = self.restrictions - Restrictions::STMT_EXPR;
+ self.parse_expr_res(restrictions, None)?
+ }
+ _ => {
+ // If an explicit return type is given, require a block to appear (RFC 968).
+ let body_lo = self.token.span;
+ self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
+ }
+ };
+
+ if let Async::Yes { span, .. } = asyncness {
+ // Feature-gate `async ||` closures.
+ self.sess.gated_spans.gate(sym::async_closure, span);
+ }
+
+ if self.token.kind == TokenKind::Semi
+ && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
+ {
+ // It is likely that the closure body is a block but where the
+ // braces have been removed. We will recover and eat the next
+ // statements later in the parsing process.
+ body = self.mk_expr_err(body.span);
+ }
+
+ let body_span = body.span;
+
+ let closure = self.mk_expr(
+ lo.to(body.span),
+ ExprKind::Closure(
+ binder,
+ capture_clause,
+ asyncness,
+ movability,
+ decl,
+ body,
+ lo.to(decl_hi),
+ ),
+ attrs,
+ );
+
+ // Disable recovery for closure body
+ let spans =
+ ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
+ self.current_closure = Some(spans);
+
+ Ok(closure)
+ }
+
+ /// Parses an optional `move` prefix to a closure-like construct.
+ fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
+ if self.eat_keyword(kw::Move) {
+ // Check for `move async` and recover
+ if self.check_keyword(kw::Async) {
+ let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
+ Err(self.incorrect_move_async_order_found(move_async_span))
+ } else {
+ Ok(CaptureBy::Value)
+ }
+ } else {
+ Ok(CaptureBy::Ref)
+ }
+ }
+
+ /// Parses the `|arg, arg|` header of a closure.
+ fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
+ let inputs = if self.eat(&token::OrOr) {
+ Vec::new()
+ } else {
+ self.expect(&token::BinOp(token::Or))?;
+ let args = self
+ .parse_seq_to_before_tokens(
+ &[&token::BinOp(token::Or), &token::OrOr],
+ SeqSep::trailing_allowed(token::Comma),
+ TokenExpectType::NoExpect,
+ |p| p.parse_fn_block_param(),
+ )?
+ .0;
+ self.expect_or()?;
+ args
+ };
+ let output =
+ self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
+
+ Ok(P(FnDecl { inputs, output }))
+ }
+
+ /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
+ fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
+ let lo = self.token.span;
+ let attrs = self.parse_outer_attributes()?;
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
+ let ty = if this.eat(&token::Colon) {
+ this.parse_ty()?
+ } else {
+ this.mk_ty(this.prev_token.span, TyKind::Infer)
+ };
+
+ Ok((
+ Param {
+ attrs: attrs.into(),
+ ty,
+ pat,
+ span: lo.to(this.token.span),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ },
+ TrailingToken::MaybeComma,
+ ))
+ })
+ }
+
+ /// Parses an `if` expression (`if` token already eaten).
+ fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let cond = self.parse_cond_expr()?;
+
+ self.parse_if_after_cond(attrs, lo, cond)
+ }
+
+ fn parse_if_after_cond(
+ &mut self,
+ attrs: AttrVec,
+ lo: Span,
+ mut cond: P<Expr>,
+ ) -> PResult<'a, P<Expr>> {
+ let cond_span = cond.span;
+ // Tries to interpret `cond` as either a missing expression if it's a block,
+ // or as an unfinished expression if it's a binop and the RHS is a block.
+ // We could probably add more recoveries here too...
+ let mut recover_block_from_condition = |this: &mut Self| {
+ let block = match &mut cond.kind {
+ ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
+ if let ExprKind::Block(_, None) = right.kind => {
+ this.error_missing_if_then_block(lo, cond_span.shrink_to_lo().to(*binop_span), true).emit();
+ std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
+ },
+ ExprKind::Block(_, None) => {
+ this.error_missing_if_cond(lo, cond_span).emit();
+ std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
+ }
+ _ => {
+ return None;
+ }
+ };
+ if let ExprKind::Block(block, _) = &block.kind {
+ Some(block.clone())
+ } else {
+ unreachable!()
+ }
+ };
+ // Parse then block
+ let thn = if self.token.is_keyword(kw::Else) {
+ if let Some(block) = recover_block_from_condition(self) {
+ block
+ } else {
+ self.error_missing_if_then_block(lo, cond_span, false).emit();
+ self.mk_block_err(cond_span.shrink_to_hi())
+ }
+ } else {
+ let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
+ let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
+ self.parse_block()?
+ } else {
+ if let Some(block) = recover_block_from_condition(self) {
+ block
+ } else {
+ // Parse block, which will always fail, but we can add a nice note to the error
+ self.parse_block().map_err(|mut err| {
+ err.span_note(
+ cond_span,
+ "the `if` expression is missing a block after this condition",
+ );
+ err
+ })?
+ }
+ };
+ self.error_on_if_block_attrs(lo, false, block.span, &attrs);
+ block
+ };
+ let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els), attrs))
+ }
+
+ fn error_missing_if_then_block(
+ &self,
+ if_span: Span,
+ cond_span: Span,
+ is_unfinished: bool,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let mut err = self.struct_span_err(
+ if_span,
+ "this `if` expression is missing a block after the condition",
+ );
+ if is_unfinished {
+ err.span_help(cond_span, "this binary operation is possibly unfinished");
+ } else {
+ err.span_help(cond_span.shrink_to_hi(), "add a block here");
+ }
+ err
+ }
+
+ fn error_missing_if_cond(
+ &self,
+ lo: Span,
+ span: Span,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let next_span = self.sess.source_map().next_point(lo);
+ let mut err = self.struct_span_err(next_span, "missing condition for `if` expression");
+ err.span_label(next_span, "expected condition here");
+ err.span_label(
+ self.sess.source_map().start_point(span),
+ "if this block is the condition of the `if` expression, then it must be followed by another block"
+ );
+ err
+ }
+
+ /// Parses the condition of a `if` or `while` expression.
+ fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
+ let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
+
+ if let ExprKind::Let(..) = cond.kind {
+ // Remove the last feature gating of a `let` expression since it's stable.
+ self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+ }
+
+ Ok(cond)
+ }
+
+ /// Parses a `let $pat = $expr` pseudo-expression.
+ fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ // This is a *approximate* heuristic that detects if `let` chains are
+ // being parsed in the right position. It's approximate because it
+ // doesn't deny all invalid `let` expressions, just completely wrong usages.
+ let not_in_chain = !matches!(
+ self.prev_token.kind,
+ TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
+ );
+ if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
+ self.struct_span_err(self.token.span, "expected expression, found `let` statement")
+ .emit();
+ }
+
+ self.bump(); // Eat `let` token
+ let lo = self.prev_token.span;
+ let pat = self.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::Yes,
+ RecoverColon::Yes,
+ CommaRecoveryMode::LikelyTuple,
+ )?;
+ self.expect(&token::Eq)?;
+ let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
+ this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
+ })?;
+ let span = lo.to(expr.span);
+ self.sess.gated_spans.gate(sym::let_chains, span);
+ Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span), attrs))
+ }
+
+ /// Parses an `else { ... }` expression (`else` token already eaten).
+ fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
+ let else_span = self.prev_token.span; // `else`
+ let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
+ let expr = if self.eat_keyword(kw::If) {
+ self.parse_if_expr(AttrVec::new())?
+ } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
+ self.parse_simple_block()?
+ } else {
+ let snapshot = self.create_snapshot_for_diagnostic();
+ let first_tok = super::token_descr(&self.token);
+ let first_tok_span = self.token.span;
+ match self.parse_expr() {
+ Ok(cond)
+ // If it's not a free-standing expression, and is followed by a block,
+ // then it's very likely the condition to an `else if`.
+ if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
+ && classify::expr_requires_semi_to_be_stmt(&cond) =>
+ {
+ self.struct_span_err(first_tok_span, format!("expected `{{`, found {first_tok}"))
+ .span_label(else_span, "expected an `if` or a block after this `else`")
+ .span_suggestion(
+ cond.span.shrink_to_lo(),
+ "add an `if` if this is the condition of a chained `else if` statement",
+ "if ",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ self.parse_if_after_cond(AttrVec::new(), cond.span.shrink_to_lo(), cond)?
+ }
+ Err(e) => {
+ e.cancel();
+ self.restore_snapshot(snapshot);
+ self.parse_simple_block()?
+ },
+ Ok(_) => {
+ self.restore_snapshot(snapshot);
+ self.parse_simple_block()?
+ },
+ }
+ };
+ self.error_on_if_block_attrs(else_span, true, expr.span, &attrs);
+ Ok(expr)
+ }
+
+ fn error_on_if_block_attrs(
+ &self,
+ ctx_span: Span,
+ is_ctx_else: bool,
+ branch_span: Span,
+ attrs: &[ast::Attribute],
+ ) {
+ let (span, last) = match attrs {
+ [] => return,
+ [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
+ };
+ let ctx = if is_ctx_else { "else" } else { "if" };
+ self.struct_span_err(last, "outer attributes are not allowed on `if` and `else` branches")
+ .span_label(branch_span, "the attributes are attached to this branch")
+ .span_label(ctx_span, format!("the branch belongs to this `{ctx}`"))
+ .span_suggestion(span, "remove the attributes", "", Applicability::MachineApplicable)
+ .emit();
+ }
+
+ /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
+ fn parse_for_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ // Record whether we are about to parse `for (`.
+ // This is used below for recovery in case of `for ( $stuff ) $block`
+ // in which case we will suggest `for $stuff $block`.
+ let begin_paren = match self.token.kind {
+ token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
+ _ => None,
+ };
+
+ let pat = self.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::Yes,
+ RecoverColon::Yes,
+ CommaRecoveryMode::LikelyTuple,
+ )?;
+ if !self.eat_keyword(kw::In) {
+ self.error_missing_in_for_loop();
+ }
+ self.check_for_for_in_in_typo(self.prev_token.span);
+ let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+ let pat = self.recover_parens_around_for_head(pat, begin_paren);
+
+ let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+
+ let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ }
+
+ fn error_missing_in_for_loop(&mut self) {
+ let (span, msg, sugg) = if self.token.is_ident_named(sym::of) {
+ // Possibly using JS syntax (#75311).
+ let span = self.token.span;
+ self.bump();
+ (span, "try using `in` here instead", "in")
+ } else {
+ (self.prev_token.span.between(self.token.span), "try adding `in` here", " in ")
+ };
+ self.struct_span_err(span, "missing `in` in `for` loop")
+ .span_suggestion_short(
+ span,
+ msg,
+ sugg,
+ // Has been misleading, at least in the past (closed Issue #48492).
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ /// Parses a `while` or `while let` expression (`while` token already eaten).
+ fn parse_while_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ let cond = self.parse_cond_expr().map_err(|mut err| {
+ err.span_label(lo, "while parsing the condition of this `while` expression");
+ err
+ })?;
+ let (iattrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
+ err.span_label(lo, "while parsing the body of this `while` expression");
+ err.span_label(cond.span, "this `while` condition successfully parsed");
+ err
+ })?;
+ attrs.extend(iattrs);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::While(cond, body, opt_label), attrs))
+ }
+
+ /// Parses `loop { ... }` (`loop` token already eaten).
+ fn parse_loop_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::Loop(body, opt_label), attrs))
+ }
+
+ pub(crate) fn eat_label(&mut self) -> Option<Label> {
+ self.token.lifetime().map(|ident| {
+ self.bump();
+ Label { ident }
+ })
+ }
+
+ /// Parses a `match ... { ... }` expression (`match` token already eaten).
+ fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let match_span = self.prev_token.span;
+ let lo = self.prev_token.span;
+ let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+ if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
+ if self.token == token::Semi {
+ e.span_suggestion_short(
+ match_span,
+ "try removing this `match`",
+ "",
+ Applicability::MaybeIncorrect, // speculative
+ );
+ }
+ if self.maybe_recover_unexpected_block_label() {
+ e.cancel();
+ self.bump();
+ } else {
+ return Err(e);
+ }
+ }
+ attrs.extend(self.parse_inner_attributes()?);
+
+ let mut arms: Vec<Arm> = Vec::new();
+ while self.token != token::CloseDelim(Delimiter::Brace) {
+ match self.parse_arm() {
+ Ok(arm) => arms.push(arm),
+ Err(mut e) => {
+ // Recover by skipping to the end of the block.
+ e.emit();
+ self.recover_stmt();
+ let span = lo.to(self.token.span);
+ if self.token == token::CloseDelim(Delimiter::Brace) {
+ self.bump();
+ }
+ return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
+ }
+ }
+ }
+ let hi = self.token.span;
+ self.bump();
+ Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
+ }
+
+ /// Attempt to recover from match arm body with statements and no surrounding braces.
+ fn parse_arm_body_missing_braces(
+ &mut self,
+ first_expr: &P<Expr>,
+ arrow_span: Span,
+ ) -> Option<P<Expr>> {
+ if self.token.kind != token::Semi {
+ return None;
+ }
+ let start_snapshot = self.create_snapshot_for_diagnostic();
+ let semi_sp = self.token.span;
+ self.bump(); // `;`
+ let mut stmts =
+ vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
+ let err = |this: &mut Parser<'_>, stmts: Vec<ast::Stmt>| {
+ let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
+ let mut err = this.struct_span_err(span, "`match` arm body without braces");
+ let (these, s, are) =
+ if stmts.len() > 1 { ("these", "s", "are") } else { ("this", "", "is") };
+ err.span_label(
+ span,
+ &format!(
+ "{these} statement{s} {are} not surrounded by a body",
+ these = these,
+ s = s,
+ are = are
+ ),
+ );
+ err.span_label(arrow_span, "while parsing the `match` arm starting here");
+ if stmts.len() > 1 {
+ err.multipart_suggestion(
+ &format!("surround the statement{s} with a body"),
+ vec![
+ (span.shrink_to_lo(), "{ ".to_string()),
+ (span.shrink_to_hi(), " }".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ );
+ } else {
+ err.span_suggestion(
+ semi_sp,
+ "use a comma to end a `match` arm expression",
+ ",",
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ this.mk_expr_err(span)
+ };
+ // We might have either a `,` -> `;` typo, or a block without braces. We need
+ // a more subtle parsing strategy.
+ loop {
+ if self.token.kind == token::CloseDelim(Delimiter::Brace) {
+ // We have reached the closing brace of the `match` expression.
+ return Some(err(self, stmts));
+ }
+ if self.token.kind == token::Comma {
+ self.restore_snapshot(start_snapshot);
+ return None;
+ }
+ let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
+ match self.parse_pat_no_top_alt(None) {
+ Ok(_pat) => {
+ if self.token.kind == token::FatArrow {
+ // Reached arm end.
+ self.restore_snapshot(pre_pat_snapshot);
+ return Some(err(self, stmts));
+ }
+ }
+ Err(err) => {
+ err.cancel();
+ }
+ }
+
+ self.restore_snapshot(pre_pat_snapshot);
+ match self.parse_stmt_without_recovery(true, ForceCollect::No) {
+ // Consume statements for as long as possible.
+ Ok(Some(stmt)) => {
+ stmts.push(stmt);
+ }
+ Ok(None) => {
+ self.restore_snapshot(start_snapshot);
+ break;
+ }
+ // We couldn't parse either yet another statement missing it's
+ // enclosing block nor the next arm's pattern or closing brace.
+ Err(stmt_err) => {
+ stmt_err.cancel();
+ self.restore_snapshot(start_snapshot);
+ break;
+ }
+ }
+ }
+ None
+ }
+
+ pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
+ // Used to check the `let_chains` and `if_let_guard` features mostly by scaning
+ // `&&` tokens.
+ fn check_let_expr(expr: &Expr) -> (bool, bool) {
+ match expr.kind {
+ ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, ref lhs, ref rhs) => {
+ let lhs_rslt = check_let_expr(lhs);
+ let rhs_rslt = check_let_expr(rhs);
+ (lhs_rslt.0 || rhs_rslt.0, false)
+ }
+ ExprKind::Let(..) => (true, true),
+ _ => (false, true),
+ }
+ }
+ let attrs = self.parse_outer_attributes()?;
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let lo = this.token.span;
+ let pat = this.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::Yes,
+ RecoverColon::Yes,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ )?;
+ let guard = if this.eat_keyword(kw::If) {
+ let if_span = this.prev_token.span;
+ let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
+ let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
+ if has_let_expr {
+ if does_not_have_bin_op {
+ // Remove the last feature gating of a `let` expression since it's stable.
+ this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+ }
+ let span = if_span.to(cond.span);
+ this.sess.gated_spans.gate(sym::if_let_guard, span);
+ }
+ Some(cond)
+ } else {
+ None
+ };
+ let arrow_span = this.token.span;
+ if let Err(mut err) = this.expect(&token::FatArrow) {
+ // We might have a `=>` -> `=` or `->` typo (issue #89396).
+ if TokenKind::FatArrow
+ .similar_tokens()
+ .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
+ {
+ err.span_suggestion(
+ this.token.span,
+ "try using a fat arrow here",
+ "=>",
+ Applicability::MaybeIncorrect,
+ );
+ err.emit();
+ this.bump();
+ } else {
+ return Err(err);
+ }
+ }
+ let arm_start_span = this.token.span;
+
+ let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
+ err.span_label(arrow_span, "while parsing the `match` arm starting here");
+ err
+ })?;
+
+ let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
+ && this.token != token::CloseDelim(Delimiter::Brace);
+
+ let hi = this.prev_token.span;
+
+ if require_comma {
+ let sm = this.sess.source_map();
+ if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
+ let span = body.span;
+ return Ok((
+ ast::Arm {
+ attrs: attrs.into(),
+ pat,
+ guard,
+ body,
+ span,
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ },
+ TrailingToken::None,
+ ));
+ }
+ this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
+ .or_else(|mut err| {
+ if this.token == token::FatArrow {
+ if let Ok(expr_lines) = sm.span_to_lines(expr.span)
+ && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
+ && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
+ && expr_lines.lines.len() == 2
+ {
+ // We check whether there's any trailing code in the parse span,
+ // if there isn't, we very likely have the following:
+ //
+ // X | &Y => "y"
+ // | -- - missing comma
+ // | |
+ // | arrow_span
+ // X | &X => "x"
+ // | - ^^ self.token.span
+ // | |
+ // | parsed until here as `"y" & X`
+ err.span_suggestion_short(
+ arm_start_span.shrink_to_hi(),
+ "missing a comma here to end this `match` arm",
+ ",",
+ Applicability::MachineApplicable,
+ );
+ return Err(err);
+ }
+ } else {
+ // FIXME(compiler-errors): We could also recover `; PAT =>` here
+
+ // Try to parse a following `PAT =>`, if successful
+ // then we should recover.
+ let mut snapshot = this.create_snapshot_for_diagnostic();
+ let pattern_follows = snapshot
+ .parse_pat_allow_top_alt(
+ None,
+ RecoverComma::Yes,
+ RecoverColon::Yes,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ )
+ .map_err(|err| err.cancel())
+ .is_ok();
+ if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
+ err.cancel();
+ this.struct_span_err(
+ hi.shrink_to_hi(),
+ "expected `,` following `match` arm",
+ )
+ .span_suggestion(
+ hi.shrink_to_hi(),
+ "missing a comma here to end this `match` arm",
+ ",",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ return Ok(true);
+ }
+ }
+ err.span_label(arrow_span, "while parsing the `match` arm starting here");
+ Err(err)
+ })?;
+ } else {
+ this.eat(&token::Comma);
+ }
+
+ Ok((
+ ast::Arm {
+ attrs: attrs.into(),
+ pat,
+ guard,
+ body: expr,
+ span: lo.to(hi),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ },
+ TrailingToken::None,
+ ))
+ })
+ }
+
+ /// Parses a `try {...}` expression (`try` token already eaten).
+ fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ if self.eat_keyword(kw::Catch) {
+ let mut error = self.struct_span_err(
+ self.prev_token.span,
+ "keyword `catch` cannot follow a `try` block",
+ );
+ error.help("try using `match` on the result of the `try` block instead");
+ error.emit();
+ Err(error)
+ } else {
+ let span = span_lo.to(body.span);
+ self.sess.gated_spans.gate(sym::try_blocks, span);
+ Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
+ }
+ }
+
+ fn is_do_catch_block(&self) -> bool {
+ self.token.is_keyword(kw::Do)
+ && self.is_keyword_ahead(1, &[kw::Catch])
+ && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
+ && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+ }
+
+ fn is_do_yeet(&self) -> bool {
+ self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
+ }
+
+ fn is_try_block(&self) -> bool {
+ self.token.is_keyword(kw::Try)
+ && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
+ && self.token.uninterpolated_span().rust_2018()
+ }
+
+ /// Parses an `async move? {...}` expression.
+ fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.expect_keyword(kw::Async)?;
+ let capture_clause = self.parse_capture_clause()?;
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ }
+
+ fn is_async_block(&self) -> bool {
+ self.token.is_keyword(kw::Async)
+ && ((
+ // `async move {`
+ self.is_keyword_ahead(1, &[kw::Move])
+ && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
+ ) || (
+ // `async {`
+ self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
+ ))
+ }
+
+ fn is_certainly_not_a_block(&self) -> bool {
+ self.look_ahead(1, |t| t.is_ident())
+ && (
+ // `{ ident, ` cannot start a block.
+ self.look_ahead(2, |t| t == &token::Comma)
+ || self.look_ahead(2, |t| t == &token::Colon)
+ && (
+ // `{ ident: token, ` cannot start a block.
+ self.look_ahead(4, |t| t == &token::Comma) ||
+ // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
+ self.look_ahead(3, |t| !t.can_begin_type())
+ )
+ )
+ }
+
+ fn maybe_parse_struct_expr(
+ &mut self,
+ qself: Option<&ast::QSelf>,
+ path: &ast::Path,
+ attrs: &AttrVec,
+ ) -> Option<PResult<'a, P<Expr>>> {
+ let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+ if struct_allowed || self.is_certainly_not_a_block() {
+ if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
+ return Some(Err(err));
+ }
+ let expr = self.parse_struct_expr(qself.cloned(), path.clone(), attrs.clone(), true);
+ if let (Ok(expr), false) = (&expr, struct_allowed) {
+ // This is a struct literal, but we don't can't accept them here.
+ self.error_struct_lit_not_allowed_here(path.span, expr.span);
+ }
+ return Some(expr);
+ }
+ None
+ }
+
+ fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
+ self.struct_span_err(sp, "struct literals are not allowed here")
+ .multipart_suggestion(
+ "surround the struct literal with parentheses",
+ vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ pub(super) fn parse_struct_fields(
+ &mut self,
+ pth: ast::Path,
+ recover: bool,
+ close_delim: Delimiter,
+ ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
+ let mut fields = Vec::new();
+ let mut base = ast::StructRest::None;
+ let mut recover_async = false;
+
+ let mut async_block_err = |e: &mut Diagnostic, span: Span| {
+ recover_async = true;
+ e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
+ e.help_use_latest_edition();
+ };
+
+ while self.token != token::CloseDelim(close_delim) {
+ if self.eat(&token::DotDot) {
+ let exp_span = self.prev_token.span;
+ // We permit `.. }` on the left-hand side of a destructuring assignment.
+ if self.check(&token::CloseDelim(close_delim)) {
+ base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
+ break;
+ }
+ match self.parse_expr() {
+ Ok(e) => base = ast::StructRest::Base(e),
+ Err(mut e) if recover => {
+ e.emit();
+ self.recover_stmt();
+ }
+ Err(e) => return Err(e),
+ }
+ self.recover_struct_comma_after_dotdot(exp_span);
+ break;
+ }
+
+ let recovery_field = self.find_struct_error_after_field_looking_code();
+ let parsed_field = match self.parse_expr_field() {
+ Ok(f) => Some(f),
+ Err(mut e) => {
+ if pth == kw::Async {
+ async_block_err(&mut e, pth.span);
+ } else {
+ e.span_label(pth.span, "while parsing this struct");
+ }
+ e.emit();
+
+ // If the next token is a comma, then try to parse
+ // what comes next as additional fields, rather than
+ // bailing out until next `}`.
+ if self.token != token::Comma {
+ self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+ if self.token != token::Comma {
+ break;
+ }
+ }
+ None
+ }
+ };
+
+ let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
+ // A shorthand field can be turned into a full field with `:`.
+ // We should point this out.
+ self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
+
+ match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
+ Ok(_) => {
+ if let Some(f) = parsed_field.or(recovery_field) {
+ // Only include the field if there's no parse error for the field name.
+ fields.push(f);
+ }
+ }
+ Err(mut e) => {
+ if pth == kw::Async {
+ async_block_err(&mut e, pth.span);
+ } else {
+ e.span_label(pth.span, "while parsing this struct");
+ if let Some(f) = recovery_field {
+ fields.push(f);
+ e.span_suggestion(
+ self.prev_token.span.shrink_to_hi(),
+ "try adding a comma",
+ ",",
+ Applicability::MachineApplicable,
+ );
+ } else if is_shorthand
+ && (AssocOp::from_token(&self.token).is_some()
+ || matches!(&self.token.kind, token::OpenDelim(_))
+ || self.token.kind == token::Dot)
+ {
+ // Looks like they tried to write a shorthand, complex expression.
+ let ident = parsed_field.expect("is_shorthand implies Some").ident;
+ e.span_suggestion(
+ ident.span.shrink_to_lo(),
+ "try naming a field",
+ &format!("{ident}: "),
+ Applicability::HasPlaceholders,
+ );
+ }
+ }
+ if !recover {
+ return Err(e);
+ }
+ e.emit();
+ self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+ self.eat(&token::Comma);
+ }
+ }
+ }
+ Ok((fields, base, recover_async))
+ }
+
+ /// Precondition: already parsed the '{'.
+ pub(super) fn parse_struct_expr(
+ &mut self,
+ qself: Option<ast::QSelf>,
+ pth: ast::Path,
+ attrs: AttrVec,
+ recover: bool,
+ ) -> PResult<'a, P<Expr>> {
+ let lo = pth.span;
+ let (fields, base, recover_async) =
+ self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
+ let span = lo.to(self.token.span);
+ self.expect(&token::CloseDelim(Delimiter::Brace))?;
+ let expr = if recover_async {
+ ExprKind::Err
+ } else {
+ ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
+ };
+ Ok(self.mk_expr(span, expr, attrs))
+ }
+
+ /// Use in case of error after field-looking code: `S { foo: () with a }`.
+ fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
+ match self.token.ident() {
+ Some((ident, is_raw))
+ if (is_raw || !ident.is_reserved())
+ && self.look_ahead(1, |t| *t == token::Colon) =>
+ {
+ Some(ast::ExprField {
+ ident,
+ span: self.token.span,
+ expr: self.mk_expr_err(self.token.span),
+ is_shorthand: false,
+ attrs: AttrVec::new(),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ })
+ }
+ _ => None,
+ }
+ }
+
+ fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
+ if self.token != token::Comma {
+ return;
+ }
+ self.struct_span_err(
+ span.to(self.prev_token.span),
+ "cannot use a comma after the base struct",
+ )
+ .span_suggestion_short(
+ self.token.span,
+ "remove this comma",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .note("the base struct must always be the last field")
+ .emit();
+ self.recover_stmt();
+ }
+
+ /// Parses `ident (COLON expr)?`.
+ fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
+ let attrs = self.parse_outer_attributes()?;
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let lo = this.token.span;
+
+ // Check if a colon exists one ahead. This means we're parsing a fieldname.
+ let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
+ let (ident, expr) = if is_shorthand {
+ // Mimic `x: x` for the `x` field shorthand.
+ let ident = this.parse_ident_common(false)?;
+ let path = ast::Path::from_ident(ident);
+ (ident, this.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
+ } else {
+ let ident = this.parse_field_name()?;
+ this.error_on_eq_field_init(ident);
+ this.bump(); // `:`
+ (ident, this.parse_expr()?)
+ };
+
+ Ok((
+ ast::ExprField {
+ ident,
+ span: lo.to(expr.span),
+ expr,
+ is_shorthand,
+ attrs: attrs.into(),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ },
+ TrailingToken::MaybeComma,
+ ))
+ })
+ }
+
+ /// Check for `=`. This means the source incorrectly attempts to
+ /// initialize a field with an eq rather than a colon.
+ fn error_on_eq_field_init(&self, field_name: Ident) {
+ if self.token != token::Eq {
+ return;
+ }
+
+ self.struct_span_err(self.token.span, "expected `:`, found `=`")
+ .span_suggestion(
+ field_name.span.shrink_to_hi().to(self.token.span),
+ "replace equals symbol with a colon",
+ ":",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ fn err_dotdotdot_syntax(&self, span: Span) {
+ self.struct_span_err(span, "unexpected token: `...`")
+ .span_suggestion(
+ span,
+ "use `..` for an exclusive range",
+ "..",
+ Applicability::MaybeIncorrect,
+ )
+ .span_suggestion(
+ span,
+ "or `..=` for an inclusive range",
+ "..=",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ fn err_larrow_operator(&self, span: Span) {
+ self.struct_span_err(span, "unexpected token: `<-`")
+ .span_suggestion(
+ span,
+ "if you meant to write a comparison against a negative value, add a \
+ space in between `<` and `-`",
+ "< -",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+ ExprKind::AssignOp(binop, lhs, rhs)
+ }
+
+ fn mk_range(
+ &mut self,
+ start: Option<P<Expr>>,
+ end: Option<P<Expr>>,
+ limits: RangeLimits,
+ ) -> ExprKind {
+ if end.is_none() && limits == RangeLimits::Closed {
+ self.inclusive_range_with_incorrect_end(self.prev_token.span);
+ ExprKind::Err
+ } else {
+ ExprKind::Range(start, end, limits)
+ }
+ }
+
+ fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
+ ExprKind::Unary(unop, expr)
+ }
+
+ fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+ ExprKind::Binary(binop, lhs, rhs)
+ }
+
+ fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
+ ExprKind::Index(expr, idx)
+ }
+
+ fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
+ ExprKind::Call(f, args)
+ }
+
+ fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
+ let span = lo.to(self.prev_token.span);
+ let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
+ self.recover_from_await_method_call();
+ await_expr
+ }
+
+ pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
+ P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
+ }
+
+ pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
+ self.mk_expr(span, ExprKind::Err, AttrVec::new())
+ }
+
+ /// Create expression span ensuring the span of the parent node
+ /// is larger than the span of lhs and rhs, including the attributes.
+ fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
+ lhs.attrs
+ .iter()
+ .find(|a| a.style == AttrStyle::Outer)
+ .map_or(lhs_span, |a| a.span)
+ .to(rhs_span)
+ }
+
+ fn collect_tokens_for_expr(
+ &mut self,
+ attrs: AttrWrapper,
+ f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, P<Expr>>,
+ ) -> PResult<'a, P<Expr>> {
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let res = f(this, attrs)?;
+ let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
+ && this.token.kind == token::Semi
+ {
+ TrailingToken::Semi
+ } else {
+ // FIXME - pass this through from the place where we know
+ // we need a comma, rather than assuming that `#[attr] expr,`
+ // always captures a trailing comma
+ TrailingToken::MaybeComma
+ };
+ Ok((res, trailing))
+ })
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
new file mode 100644
index 000000000..1acfd93d8
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -0,0 +1,350 @@
+use super::{ForceCollect, Parser, TrailingToken};
+
+use rustc_ast::token;
+use rustc_ast::{
+ self as ast, Attribute, GenericBounds, GenericParam, GenericParamKind, WhereClause,
+};
+use rustc_errors::{Applicability, PResult};
+use rustc_span::symbol::kw;
+
+impl<'a> Parser<'a> {
+ /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
+ ///
+ /// ```text
+ /// BOUND = LT_BOUND (e.g., `'a`)
+ /// ```
+ fn parse_lt_param_bounds(&mut self) -> GenericBounds {
+ let mut lifetimes = Vec::new();
+ while self.check_lifetime() {
+ lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
+
+ if !self.eat_plus() {
+ break;
+ }
+ }
+ lifetimes
+ }
+
+ /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
+ fn parse_ty_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
+ let ident = self.parse_ident()?;
+
+ // Parse optional colon and param bounds.
+ let mut colon_span = None;
+ let bounds = if self.eat(&token::Colon) {
+ colon_span = Some(self.prev_token.span);
+ self.parse_generic_bounds(colon_span)?
+ } else {
+ Vec::new()
+ };
+
+ let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
+
+ Ok(GenericParam {
+ ident,
+ id: ast::DUMMY_NODE_ID,
+ attrs: preceding_attrs.into(),
+ bounds,
+ kind: GenericParamKind::Type { default },
+ is_placeholder: false,
+ colon_span,
+ })
+ }
+
+ pub(crate) fn parse_const_param(
+ &mut self,
+ preceding_attrs: Vec<Attribute>,
+ ) -> PResult<'a, GenericParam> {
+ let const_span = self.token.span;
+
+ self.expect_keyword(kw::Const)?;
+ let ident = self.parse_ident()?;
+ self.expect(&token::Colon)?;
+ let ty = self.parse_ty()?;
+
+ // Parse optional const generics default value.
+ let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
+
+ Ok(GenericParam {
+ ident,
+ id: ast::DUMMY_NODE_ID,
+ attrs: preceding_attrs.into(),
+ bounds: Vec::new(),
+ kind: GenericParamKind::Const { ty, kw_span: const_span, default },
+ is_placeholder: false,
+ colon_span: None,
+ })
+ }
+
+ /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
+ /// a trailing comma and erroneous trailing attributes.
+ pub(super) fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
+ let mut params = Vec::new();
+ let mut done = false;
+ while !done {
+ let attrs = self.parse_outer_attributes()?;
+ let param =
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ if this.eat_keyword_noexpect(kw::SelfUpper) {
+ // `Self` as a generic param is invalid. Here we emit the diagnostic and continue parsing
+ // as if `Self` never existed.
+ this.struct_span_err(
+ this.prev_token.span,
+ "unexpected keyword `Self` in generic parameters",
+ )
+ .note("you cannot use `Self` as a generic parameter because it is reserved for associated items")
+ .emit();
+
+ this.eat(&token::Comma);
+ }
+
+ let param = if this.check_lifetime() {
+ let lifetime = this.expect_lifetime();
+ // Parse lifetime parameter.
+ let (colon_span, bounds) = if this.eat(&token::Colon) {
+ (Some(this.prev_token.span), this.parse_lt_param_bounds())
+ } else {
+ (None, Vec::new())
+ };
+ Some(ast::GenericParam {
+ ident: lifetime.ident,
+ id: lifetime.id,
+ attrs: attrs.into(),
+ bounds,
+ kind: ast::GenericParamKind::Lifetime,
+ is_placeholder: false,
+ colon_span,
+ })
+ } else if this.check_keyword(kw::Const) {
+ // Parse const parameter.
+ Some(this.parse_const_param(attrs)?)
+ } else if this.check_ident() {
+ // Parse type parameter.
+ Some(this.parse_ty_param(attrs)?)
+ } else if this.token.can_begin_type() {
+ // Trying to write an associated type bound? (#26271)
+ let snapshot = this.create_snapshot_for_diagnostic();
+ match this.parse_ty_where_predicate() {
+ Ok(where_predicate) => {
+ this.struct_span_err(
+ where_predicate.span(),
+ "bounds on associated types do not belong here",
+ )
+ .span_label(where_predicate.span(), "belongs in `where` clause")
+ .emit();
+ // FIXME - try to continue parsing other generics?
+ return Ok((None, TrailingToken::None));
+ }
+ Err(err) => {
+ err.cancel();
+ // FIXME - maybe we should overwrite 'self' outside of `collect_tokens`?
+ this.restore_snapshot(snapshot);
+ return Ok((None, TrailingToken::None));
+ }
+ }
+ } else {
+ // Check for trailing attributes and stop parsing.
+ if !attrs.is_empty() {
+ if !params.is_empty() {
+ this.struct_span_err(
+ attrs[0].span,
+ "trailing attribute after generic parameter",
+ )
+ .span_label(attrs[0].span, "attributes must go before parameters")
+ .emit();
+ } else {
+ this.struct_span_err(
+ attrs[0].span,
+ "attribute without generic parameters",
+ )
+ .span_label(
+ attrs[0].span,
+ "attributes are only permitted when preceding parameters",
+ )
+ .emit();
+ }
+ }
+ return Ok((None, TrailingToken::None));
+ };
+
+ if !this.eat(&token::Comma) {
+ done = true;
+ }
+ // We just ate the comma, so no need to use `TrailingToken`
+ Ok((param, TrailingToken::None))
+ })?;
+
+ if let Some(param) = param {
+ params.push(param);
+ } else {
+ break;
+ }
+ }
+ Ok(params)
+ }
+
+ /// Parses a set of optional generic type parameter declarations. Where
+ /// clauses are not parsed here, and must be added later via
+ /// `parse_where_clause()`.
+ ///
+ /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
+ /// | ( < lifetimes , typaramseq ( , )? > )
+ /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
+ pub(super) fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
+ let span_lo = self.token.span;
+ let (params, span) = if self.eat_lt() {
+ let params = self.parse_generic_params()?;
+ self.expect_gt()?;
+ (params, span_lo.to(self.prev_token.span))
+ } else {
+ (vec![], self.prev_token.span.shrink_to_hi())
+ };
+ Ok(ast::Generics {
+ params,
+ where_clause: WhereClause {
+ has_where_token: false,
+ predicates: Vec::new(),
+ span: self.prev_token.span.shrink_to_hi(),
+ },
+ span,
+ })
+ }
+
+ /// Parses an optional where-clause and places it in `generics`.
+ ///
+ /// ```ignore (only-for-syntax-highlight)
+ /// where T : Trait<U, V> + 'b, 'a : 'b
+ /// ```
+ pub(super) fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
+ let mut where_clause = WhereClause {
+ has_where_token: false,
+ predicates: Vec::new(),
+ span: self.prev_token.span.shrink_to_hi(),
+ };
+
+ if !self.eat_keyword(kw::Where) {
+ return Ok(where_clause);
+ }
+ where_clause.has_where_token = true;
+ let lo = self.prev_token.span;
+
+ // We are considering adding generics to the `where` keyword as an alternative higher-rank
+ // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
+ // change we parse those generics now, but report an error.
+ if self.choose_generics_over_qpath(0) {
+ let generics = self.parse_generics()?;
+ self.struct_span_err(
+ generics.span,
+ "generic parameters on `where` clauses are reserved for future use",
+ )
+ .span_label(generics.span, "currently unsupported")
+ .emit();
+ }
+
+ loop {
+ let lo = self.token.span;
+ if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
+ let lifetime = self.expect_lifetime();
+ // Bounds starting with a colon are mandatory, but possibly empty.
+ self.expect(&token::Colon)?;
+ let bounds = self.parse_lt_param_bounds();
+ where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
+ ast::WhereRegionPredicate {
+ span: lo.to(self.prev_token.span),
+ lifetime,
+ bounds,
+ },
+ ));
+ } else if self.check_type() {
+ where_clause.predicates.push(self.parse_ty_where_predicate()?);
+ } else {
+ break;
+ }
+
+ let prev_token = self.prev_token.span;
+ let ate_comma = self.eat(&token::Comma);
+
+ if self.eat_keyword_noexpect(kw::Where) {
+ let msg = "cannot define duplicate `where` clauses on an item";
+ let mut err = self.struct_span_err(self.token.span, msg);
+ err.span_label(lo, "previous `where` clause starts here");
+ err.span_suggestion_verbose(
+ prev_token.shrink_to_hi().to(self.prev_token.span),
+ "consider joining the two `where` clauses into one",
+ ",",
+ Applicability::MaybeIncorrect,
+ );
+ err.emit();
+ } else if !ate_comma {
+ break;
+ }
+ }
+
+ where_clause.span = lo.to(self.prev_token.span);
+ Ok(where_clause)
+ }
+
+ fn parse_ty_where_predicate(&mut self) -> PResult<'a, ast::WherePredicate> {
+ let lo = self.token.span;
+ // Parse optional `for<'a, 'b>`.
+ // This `for` is parsed greedily and applies to the whole predicate,
+ // the bounded type can have its own `for` applying only to it.
+ // Examples:
+ // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
+ // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
+ // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
+ let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+
+ // Parse type with mandatory colon and (possibly empty) bounds,
+ // or with mandatory equality sign and the second type.
+ let ty = self.parse_ty_for_where_clause()?;
+ if self.eat(&token::Colon) {
+ let bounds = self.parse_generic_bounds(Some(self.prev_token.span))?;
+ Ok(ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
+ span: lo.to(self.prev_token.span),
+ bound_generic_params: lifetime_defs,
+ bounded_ty: ty,
+ bounds,
+ }))
+ // FIXME: Decide what should be used here, `=` or `==`.
+ // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
+ } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
+ let rhs_ty = self.parse_ty()?;
+ Ok(ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
+ span: lo.to(self.prev_token.span),
+ lhs_ty: ty,
+ rhs_ty,
+ id: ast::DUMMY_NODE_ID,
+ }))
+ } else {
+ self.maybe_recover_bounds_doubled_colon(&ty)?;
+ self.unexpected()
+ }
+ }
+
+ pub(super) fn choose_generics_over_qpath(&self, start: usize) -> bool {
+ // There's an ambiguity between generic parameters and qualified paths in impls.
+ // If we see `<` it may start both, so we have to inspect some following tokens.
+ // The following combinations can only start generics,
+ // but not qualified paths (with one exception):
+ // `<` `>` - empty generic parameters
+ // `<` `#` - generic parameters with attributes
+ // `<` (LIFETIME|IDENT) `>` - single generic parameter
+ // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
+ // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
+ // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
+ // `<` const - generic const parameter
+ // The only truly ambiguous case is
+ // `<` IDENT `>` `::` IDENT ...
+ // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
+ // because this is what almost always expected in practice, qualified paths in impls
+ // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
+ self.look_ahead(start, |t| t == &token::Lt)
+ && (self.look_ahead(start + 1, |t| t == &token::Pound || t == &token::Gt)
+ || self.look_ahead(start + 1, |t| t.is_lifetime() || t.is_ident())
+ && self.look_ahead(start + 2, |t| {
+ matches!(t.kind, token::Gt | token::Comma | token::Colon | token::Eq)
+ })
+ || self.is_keyword_ahead(start + 1, &[kw::Const]))
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
new file mode 100644
index 000000000..567072925
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -0,0 +1,2426 @@
+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, Delimiter, 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;
+use rustc_span::lev_distance::lev_distance;
+use rustc_span::source_map::{self, Span};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::DUMMY_SP;
+
+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, 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 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(Delimiter::Brace))?;
+ let (mut inner_attrs, items, inner_span) =
+ self.parse_mod(&token::CloseDelim(Delimiter::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>>, ModSpans)> {
+ let lo = self.token.span;
+ let attrs = self.parse_inner_attributes()?;
+
+ let post_attr_lo = self.token.span;
+ 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);
+ }
+ }
+
+ 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>> {
+ let attrs = self.parse_outer_attributes()?;
+ 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>> {
+ // 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 && 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, fn_parse_mode);
+ 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,
+ 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)?;
+ 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 `{vs}` is not followed by an item"))
+ .span_label(vis.span, "the visibility")
+ .help(&format!("you likely meant to define an item, e.g., `{vs} fn foo() {{}}`"))
+ .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,
+ fn_parse_mode: FnParseMode,
+ ) -> 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) {
+ self.parse_use_item()?
+ } else if self.check_fn_front_matter(def_final) {
+ // FUNCTION ITEM
+ let (ident, sig, generics, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis)?;
+ (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();
+ 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 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))
+ {
+ 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 macros_allowed && self.check_path() {
+ // MACRO INVOCATION ITEM
+ (Ident::empty(), ItemKind::MacCall(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.struct_span_err(span, format!("expected item, found {token_name}"))
+ .span_suggestion_short(
+ span,
+ "items are imported using the `use` keyword",
+ "use",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ 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.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`
+ }
+
+ /// 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(Delimiter::Brace)) {
+ // possible public struct definition where `struct` was forgotten
+ let ident = self.parse_ident().unwrap();
+ let msg = format!("add `struct` here to parse `{ident}` as a public struct");
+ let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
+ err.span_suggestion_short(
+ sp,
+ &msg,
+ " struct ",
+ Applicability::MaybeIncorrect, // speculative
+ );
+ Err(err)
+ } else if self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Parenthesis)) {
+ let ident = self.parse_ident().unwrap();
+ self.bump(); // `(`
+ let kw_name = self.recover_first_param();
+ self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::Yes);
+ let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
+ self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
+ self.bump(); // `{`
+ ("fn", kw_name, false)
+ } else if self.check(&token::OpenDelim(Delimiter::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 `{kw}` for {kw_name} definition");
+ let mut err = self.struct_span_err(sp, &msg);
+ if !ambiguous {
+ self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+ let suggestion =
+ format!("add `{kw}` here to parse `{ident}` as a public {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(Delimiter::Parenthesis)) {
+ ("fn", self.recover_first_param(), false)
+ } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
+ ("struct", "struct", false)
+ } else {
+ ("fn` or `struct", "function or struct", true)
+ };
+ let msg = format!("missing `{kw}` for {kw_name} definition");
+ let mut err = self.struct_span_err(sp, &msg);
+ if !ambiguous {
+ err.span_suggestion_short(
+ sp,
+ &format!("add `{kw}` here to parse `{ident}` as a public {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)?; // `!`
+ match self.parse_mac_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, prior_type_ascription: self.last_type_ascription })
+ }
+
+ Err(mut err) => {
+ // Maybe the user misspelled `macro_rules` (issue #91227)
+ if self.token.is_ident()
+ && path.segments.len() == 1
+ && lev_distance("macro_rules", &path.segments[0].ident.to_string(), 3).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.struct_span_err(end.span, msg);
+ if end.is_doc_comment() {
+ err.span_label(end.span, "this doc comment doesn't document anything");
+ }
+ if end.meta_kind().is_some() {
+ 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 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")
+ .span_suggestion(
+ span,
+ "add a trait here",
+ " Trait ",
+ Applicability::HasPlaceholders,
+ )
+ .span_suggestion(
+ span.to(self.token.span),
+ "for an inherent impl, drop this `for`",
+ "",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ 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
+ 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 ",
+ 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::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_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(Delimiter::Brace))?;
+ attrs.append(&mut self.parse_inner_attributes()?);
+
+ let mut items = Vec::new();
+ while !self.eat(&token::CloseDelim(Delimiter::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(Delimiter::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(Delimiter::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(Delimiter::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 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(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)?;
+ generics.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(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(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:
+ /// ```ebnf
+ /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
+ /// ```
+ /// 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(None)? } 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 = (
+ TyAliasWhereClause(before_where_clause.has_where_token, before_where_clause.span),
+ TyAliasWhereClause(after_where_clause.has_where_token, after_where_clause.span),
+ );
+ let where_predicates_split = before_where_clause.predicates.len();
+ let mut predicates = before_where_clause.predicates;
+ predicates.extend(after_where_clause.predicates.into_iter());
+ 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,
+ where_predicates_split,
+ 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: Vec::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::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(Delimiter::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
+ ///
+ /// ```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 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 = ident.name.to_string();
+ 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>,
+ 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))
+ {
+ let mut err = self.expect(&token::OpenDelim(Delimiter::Brace)).unwrap_err();
+ 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(_, 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!("{descr} is not supported in {ctx}"))
+ .help(&format!("consider moving the {descr} out to a nearby module scope"))
+ .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 ",
+ 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(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.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",
+ 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(recovery_error) => {
+ // Recovery failed, raise the "expected identifier" error
+ recovery_error.cancel();
+ return Err(err);
+ }
+ };
+
+ match impl_info.1 {
+ ItemKind::Impl(box Impl { 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 `{kind}` item"));
+ err.span_suggestion(
+ id.span,
+ "provide a type for the item",
+ format!("{id}: <type>"),
+ 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> {
+ if self.token.is_keyword(kw::Struct) {
+ let mut err = self.struct_span_err(
+ self.prev_token.span.to(self.token.span),
+ "`enum` and `struct` are mutually exclusive",
+ );
+ err.span_suggestion(
+ self.prev_token.span.to(self.token.span),
+ "replace `enum struct` with",
+ "enum",
+ Applicability::MachineApplicable,
+ );
+ if self.look_ahead(1, |t| t.is_ident()) {
+ self.bump();
+ err.emit();
+ } else {
+ return Err(err);
+ }
+ }
+
+ 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(Delimiter::Brace, |p| p.parse_enum_variant())
+ .map_err(|e| {
+ self.recover_stmt();
+ e
+ })?;
+
+ let enum_definition = EnumDef { variants: variants.into_iter().flatten().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_field_ident("enum", vlo)?;
+
+ let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
+ // Parse a struct variant.
+ let (fields, recovered) = this.parse_record_struct_body("struct", false)?;
+ VariantData::Struct(fields, recovered)
+ } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ 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.into(),
+ 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("struct", generics.where_clause.has_where_token)?;
+ 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(Delimiter::Brace) {
+ let (fields, recovered) =
+ self.parse_record_struct_body("struct", generics.where_clause.has_where_token)?;
+ VariantData::Struct(fields, recovered)
+ // 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 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("union", generics.where_clause.has_where_token)?;
+ VariantData::Struct(fields, recovered)
+ } else if self.token == token::OpenDelim(Delimiter::Brace) {
+ let (fields, recovered) =
+ self.parse_record_struct_body("union", generics.where_clause.has_where_token)?;
+ 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,
+ adt_ty: &str,
+ parsed_where: bool,
+ ) -> PResult<'a, (Vec<FieldDef>, /* recovered */ bool)> {
+ let mut fields = Vec::new();
+ let mut recovered = false;
+ if self.eat(&token::OpenDelim(Delimiter::Brace)) {
+ while self.token != token::CloseDelim(Delimiter::Brace) {
+ let field = self.parse_field_def(adt_ty).map_err(|e| {
+ self.consume_block(Delimiter::Brace, ConsumeClosingDelim::No);
+ recovered = true;
+ e
+ });
+ match field {
+ Ok(field) => fields.push(field),
+ Err(mut err) => {
+ err.emit();
+ 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.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))
+ }
+
+ 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: attrs.into(),
+ 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> {
+ 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(adt_ty, lo, vis, attrs)?, TrailingToken::None))
+ })
+ }
+
+ /// Parses a structure field declaration.
+ fn parse_single_struct_field(
+ &mut self,
+ adt_ty: &str,
+ lo: Span,
+ vis: Visibility,
+ attrs: Vec<Attribute>,
+ ) -> 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;
+ }
+ match self.token.kind {
+ token::Comma => {
+ self.bump();
+ }
+ token::CloseDelim(Delimiter::Brace) => {}
+ token::DocComment(..) => {
+ let previous_span = self.prev_token.span;
+ let mut err = self.span_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(Delimiter::Brace) {
+ err.emit();
+ } else {
+ if !seen_comma {
+ let sp = self.sess.source_map().next_point(previous_span);
+ err.span_suggestion(
+ sp,
+ "missing comma here",
+ ",",
+ 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(Delimiter::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
+ // NOTE(eddyb) this was `.cancel()`, but `err`
+ // gets returned, so we can't fully defuse it.
+ err.delay_as_bug();
+ }
+ }
+ }
+
+ if self.token.is_ident() {
+ // This is likely another field; emit the diagnostic and keep going
+ err.span_suggestion(
+ sp,
+ "try adding a comma",
+ ",",
+ 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().is_some());
+ } else {
+ return Err(err);
+ }
+ }
+ }
+ Ok(a_var)
+ }
+
+ fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
+ if let Err(mut err) = self.expect(&token::Colon) {
+ let sm = self.sess.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.span_suggestion_short(
+ self.prev_token.span,
+ "field names and their types are separated with `:`",
+ ":",
+ Applicability::MachineApplicable,
+ );
+ err.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: Vec<Attribute>,
+ ) -> PResult<'a, FieldDef> {
+ let name = self.parse_field_ident(adt_ty, lo)?;
+ self.expect_field_ty_separator()?;
+ let ty = self.parse_ty()?;
+ if self.token.kind == token::Colon && self.look_ahead(1, |tok| tok.kind != token::Colon) {
+ self.struct_span_err(self.token.span, "found single colon in a struct field type path")
+ .span_suggestion_verbose(
+ self.token.span,
+ "write a path separator here",
+ "::",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+ if self.token.kind == token::Eq {
+ self.bump();
+ let const_expr = self.parse_anon_const_expr()?;
+ let sp = ty.span.shrink_to_hi().to(const_expr.value.span);
+ self.struct_span_err(sp, "default values on `struct` fields aren't supported")
+ .span_suggestion(
+ sp,
+ "remove this unsupported default value",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+ Ok(FieldDef {
+ span: lo.to(self.prev_token.span),
+ ident: Some(name),
+ vis,
+ id: DUMMY_NODE_ID,
+ ty,
+ attrs: attrs.into(),
+ 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()?;
+ if !is_raw && ident.is_reserved() {
+ let err = if self.check_fn_front_matter(false) {
+ let inherited_vis = Visibility {
+ span: rustc_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 };
+ if let Err(mut db) =
+ self.parse_fn(&mut Vec::new(), fn_parse_mode, lo, &inherited_vis)
+ {
+ db.delay_as_bug();
+ }
+ let mut err = self.struct_span_err(
+ lo.to(self.prev_token.span),
+ &format!("functions are not allowed in {adt_ty} definitions"),
+ );
+ err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
+ err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
+ err
+ } else {
+ self.expected_ident_found()
+ };
+ 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_mac_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)) {
+ return 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(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 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.struct_span_err(macro_rules_span, "expected `!` after `macro_rules`")
+ .span_suggestion(
+ macro_rules_span,
+ "add a `!`",
+ "macro_rules!",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ 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.struct_span_err(span, "macro names aren't followed by a `!`")
+ .span_suggestion(span, "remove the `!`", "", Applicability::MachineApplicable)
+ .emit();
+ }
+
+ 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]",
+ 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",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .help(&format!("try adjusting the macro to put `{vstr}` inside the invocation"))
+ .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",
+ );
+ // 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() {
+ 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 */ }",
+ Applicability::HasPlaceholders,
+ );
+ }
+ err.span_suggestion(
+ 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.struct_span_err(
+ kw_token.span,
+ &format!("`{kw_str}` definition cannot be nested inside `{keyword}`"),
+ )
+ .span_suggestion(
+ item.unwrap().span,
+ &format!("consider creating a new `{kw_str}` definition instead of nesting"),
+ "",
+ 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.
+///
+/// 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 Vec<Attribute>,
+ fn_parse_mode: FnParseMode,
+ sig_lo: Span,
+ vis: &Visibility,
+ ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
+ let header = self.parse_fn_front_matter(vis)?; // `const ... fn`
+ let ident = self.parse_ident()?; // `foo`
+ let mut generics = self.parse_generics()?; // `<'a, T, ...>`
+ let decl =
+ self.parse_fn_decl(fn_parse_mode.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, 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 Vec<Attribute>,
+ 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;
+ (Vec::new(), None)
+ } else if self.check(&token::OpenDelim(Delimiter::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() = $expr;`.
+ self.bump(); // `=`
+ let eq_sp = self.prev_token.span;
+ let _ = self.parse_expr()?;
+ self.expect_semi()?; // `;`
+ let span = eq_sp.to(self.prev_token.span);
+ self.struct_span_err(span, "function body cannot be `= expression;`")
+ .multipart_suggestion(
+ "surround the expression with `{` and `}` instead of `=` and `;`",
+ vec![(eq_sp, "{".to_string()), (self.prev_token.span, " }".to_string())],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ (Vec::new(), Some(self.mk_block_err(span)))
+ } else {
+ let expected = if req_body {
+ &[token::OpenDelim(Delimiter::Brace)][..]
+ } else {
+ &[token::Semi, token::OpenDelim(Delimiter::Brace)]
+ };
+ if let Err(mut err) = self.expected_one_of_not_found(&[], &expected) {
+ if self.token.kind == token::CloseDelim(Delimiter::Brace) {
+ // The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
+ // the AST for typechecking.
+ err.span_label(ident.span, "while parsing this `fn`");
+ err.emit();
+ } else {
+ return Err(err);
+ }
+ }
+ (Vec::new(), None)
+ };
+ attrs.extend(inner_attrs);
+ Ok(body)
+ }
+
+ /// Is the current token the start of an `FnHeader` / not a valid parse?
+ ///
+ /// `check_pub` adds additional `pub` to the checks in case users place it
+ /// wrongly, can be used to ensure `pub` never comes after `default`.
+ pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
+ // We use an over-approximation here.
+ // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
+ // `pub` is added in case users got confused with the ordering like `async pub fn`,
+ // only if it wasn't preceded by `default` as `default pub` is invalid.
+ let quals: &[Symbol] = if check_pub {
+ &[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
+ } else {
+ &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
+ };
+ self.check_keyword(kw::Fn) // Definitely an `fn`.
+ // `$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:
+ ///
+ /// ```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) -> PResult<'a, FnHeader> {
+ let sp_start = self.token.span;
+ let constness = self.parse_constness();
+
+ let async_start_sp = self.token.span;
+ let asyncness = self.parse_asyncness();
+
+ let unsafe_start_sp = self.token.span;
+ let unsafety = self.parse_unsafety();
+
+ let ext_start_sp = self.token.span;
+ 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) => {
+ // Qualifier keywords ordering check
+ enum WrongKw {
+ Duplicated(Span),
+ Misplaced(Span),
+ }
+
+ // 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 => Some(WrongKw::Misplaced(async_start_sp)),
+ }
+ } else if self.check_keyword(kw::Async) {
+ match asyncness {
+ Async::Yes { span, .. } => Some(WrongKw::Duplicated(span)),
+ Async::No => Some(WrongKw::Misplaced(unsafe_start_sp)),
+ }
+ } else if self.check_keyword(kw::Unsafe) {
+ match unsafety {
+ Unsafe::Yes(sp) => Some(WrongKw::Duplicated(sp)),
+ Unsafe::No => 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");
+ }
+ }
+ }
+ 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_use_latest_edition()
+ .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(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))))
+ });
+ // ...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(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();
+ }
+ 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(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(|e| e.cancel())
+ {
+ Ok(Some(_)) => "method",
+ _ => "function",
+ }
+ }
+}
+
+enum IsMacroRulesItem {
+ Yes { has_bang: bool },
+ No,
+}
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
new file mode 100644
index 000000000..0c523ad22
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -0,0 +1,1481 @@
+pub mod attr;
+mod attr_wrapper;
+mod diagnostics;
+mod expr;
+mod generics;
+mod item;
+mod nonterminal;
+mod pat;
+mod path;
+mod stmt;
+mod ty;
+
+use crate::lexer::UnmatchedBrace;
+pub use attr_wrapper::AttrWrapper;
+pub use diagnostics::AttemptLocalParseRecovery;
+use diagnostics::Error;
+pub(crate) use item::FnParseMode;
+pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
+pub use path::PathStyle;
+
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, Nonterminal, Token, TokenKind};
+use rustc_ast::tokenstream::AttributesData;
+use rustc_ast::tokenstream::{self, DelimSpan, Spacing};
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast::AttrId;
+use rustc_ast::DUMMY_NODE_ID;
+use rustc_ast::{self as ast, AnonConst, AttrStyle, AttrVec, Const, Extern};
+use rustc_ast::{Async, Expr, ExprKind, MacArgs, MacArgsEq, MacDelimiter, Mutability, StrLit};
+use rustc_ast::{HasAttrs, HasTokens, Unsafe, Visibility, VisibilityKind};
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::PResult;
+use rustc_errors::{
+ struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, FatalError, MultiSpan,
+};
+use rustc_session::parse::ParseSess;
+use rustc_span::source_map::{Span, DUMMY_SP};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use tracing::debug;
+
+use std::ops::Range;
+use std::{cmp, mem, slice};
+
+bitflags::bitflags! {
+ struct Restrictions: u8 {
+ const STMT_EXPR = 1 << 0;
+ const NO_STRUCT_LITERAL = 1 << 1;
+ const CONST_EXPR = 1 << 2;
+ const ALLOW_LET = 1 << 3;
+ }
+}
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+enum SemiColonMode {
+ Break,
+ Ignore,
+ Comma,
+}
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+enum BlockMode {
+ Break,
+ Ignore,
+}
+
+/// Whether or not we should force collection of tokens for an AST node,
+/// regardless of whether or not it has attributes
+#[derive(Clone, Copy, PartialEq)]
+pub enum ForceCollect {
+ Yes,
+ No,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum TrailingToken {
+ None,
+ Semi,
+ /// If the trailing token is a comma, then capture it
+ /// Otherwise, ignore the trailing token
+ MaybeComma,
+}
+
+/// Like `maybe_whole_expr`, but for things other than expressions.
+#[macro_export]
+macro_rules! maybe_whole {
+ ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
+ if let token::Interpolated(nt) = &$p.token.kind {
+ if let token::$constructor(x) = &**nt {
+ let $x = x.clone();
+ $p.bump();
+ return Ok($e);
+ }
+ }
+ };
+}
+
+/// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
+#[macro_export]
+macro_rules! maybe_recover_from_interpolated_ty_qpath {
+ ($self: expr, $allow_qpath_recovery: expr) => {
+ if $allow_qpath_recovery
+ && $self.look_ahead(1, |t| t == &token::ModSep)
+ && let token::Interpolated(nt) = &$self.token.kind
+ && let token::NtTy(ty) = &**nt
+ {
+ let ty = ty.clone();
+ $self.bump();
+ return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_token.span, ty);
+ }
+ };
+}
+
+#[derive(Clone)]
+pub struct Parser<'a> {
+ pub sess: &'a ParseSess,
+ /// The current token.
+ pub token: Token,
+ /// The spacing for the current token
+ pub token_spacing: Spacing,
+ /// The previous token.
+ pub prev_token: Token,
+ pub capture_cfg: bool,
+ restrictions: Restrictions,
+ expected_tokens: Vec<TokenType>,
+ // Important: This must only be advanced from `bump` to ensure that
+ // `token_cursor.num_next_calls` is updated properly.
+ token_cursor: TokenCursor,
+ desugar_doc_comments: bool,
+ /// This field is used to keep track of how many left angle brackets we have seen. This is
+ /// required in order to detect extra leading left angle brackets (`<` characters) and error
+ /// appropriately.
+ ///
+ /// See the comments in the `parse_path_segment` function for more details.
+ unmatched_angle_bracket_count: u32,
+ max_angle_bracket_count: u32,
+ /// A list of all unclosed delimiters found by the lexer. If an entry is used for error recovery
+ /// it gets removed from here. Every entry left at the end gets emitted as an independent
+ /// error.
+ pub(super) unclosed_delims: Vec<UnmatchedBrace>,
+ last_unexpected_token_span: Option<Span>,
+ /// Span pointing at the `:` for the last type ascription the parser has seen, and whether it
+ /// looked like it could have been a mistyped path or literal `Option:Some(42)`).
+ pub last_type_ascription: Option<(Span, bool /* likely path typo */)>,
+ /// If present, this `Parser` is not parsing Rust code but rather a macro call.
+ subparser_name: Option<&'static str>,
+ capture_state: CaptureState,
+ /// This allows us to recover when the user forget to add braces around
+ /// multiple statements in the closure body.
+ pub current_closure: Option<ClosureSpans>,
+}
+
+// This type is used a lot, e.g. it's cloned when matching many declarative macro rules. Make sure
+// it doesn't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(Parser<'_>, 328);
+
+/// Stores span information about a closure.
+#[derive(Clone)]
+pub struct ClosureSpans {
+ pub whole_closure: Span,
+ pub closing_pipe: Span,
+ pub body: Span,
+}
+
+/// Indicates a range of tokens that should be replaced by
+/// the tokens in the provided vector. This is used in two
+/// places during token collection:
+///
+/// 1. During the parsing of an AST node that may have a `#[derive]`
+/// attribute, we parse a nested AST node that has `#[cfg]` or `#[cfg_attr]`
+/// In this case, we use a `ReplaceRange` to replace the entire inner AST node
+/// with `FlatToken::AttrTarget`, allowing us to perform eager cfg-expansion
+/// on an `AttrAnnotatedTokenStream`
+///
+/// 2. When we parse an inner attribute while collecting tokens. We
+/// remove inner attributes from the token stream entirely, and
+/// instead track them through the `attrs` field on the AST node.
+/// This allows us to easily manipulate them (for example, removing
+/// the first macro inner attribute to invoke a proc-macro).
+/// When create a `TokenStream`, the inner attributes get inserted
+/// into the proper place in the token stream.
+pub type ReplaceRange = (Range<u32>, Vec<(FlatToken, Spacing)>);
+
+/// Controls how we capture tokens. Capturing can be expensive,
+/// so we try to avoid performing capturing in cases where
+/// we will never need an `AttrAnnotatedTokenStream`
+#[derive(Copy, Clone)]
+pub enum Capturing {
+ /// We aren't performing any capturing - this is the default mode.
+ No,
+ /// We are capturing tokens
+ Yes,
+}
+
+#[derive(Clone)]
+struct CaptureState {
+ capturing: Capturing,
+ replace_ranges: Vec<ReplaceRange>,
+ inner_attr_ranges: FxHashMap<AttrId, ReplaceRange>,
+}
+
+impl<'a> Drop for Parser<'a> {
+ fn drop(&mut self) {
+ emit_unclosed_delims(&mut self.unclosed_delims, &self.sess);
+ }
+}
+
+#[derive(Clone)]
+struct TokenCursor {
+ // The current (innermost) frame. `frame` and `stack` could be combined,
+ // but it's faster to have them separately to access `frame` directly
+ // rather than via something like `stack.last().unwrap()` or
+ // `stack[stack.len() - 1]`.
+ frame: TokenCursorFrame,
+ // Additional frames that enclose `frame`.
+ stack: Vec<TokenCursorFrame>,
+ desugar_doc_comments: bool,
+ // Counts the number of calls to `{,inlined_}next`.
+ num_next_calls: usize,
+ // During parsing, we may sometimes need to 'unglue' a
+ // glued token into two component tokens
+ // (e.g. '>>' into '>' and '>), so that the parser
+ // can consume them one at a time. This process
+ // bypasses the normal capturing mechanism
+ // (e.g. `num_next_calls` will not be incremented),
+ // since the 'unglued' tokens due not exist in
+ // the original `TokenStream`.
+ //
+ // If we end up consuming both unglued tokens,
+ // then this is not an issue - we'll end up
+ // capturing the single 'glued' token.
+ //
+ // However, in certain circumstances, we may
+ // want to capture just the first 'unglued' token.
+ // For example, capturing the `Vec<u8>`
+ // in `Option<Vec<u8>>` requires us to unglue
+ // the trailing `>>` token. The `break_last_token`
+ // field is used to track this token - it gets
+ // appended to the captured stream when
+ // we evaluate a `LazyTokenStream`
+ break_last_token: bool,
+}
+
+#[derive(Clone)]
+struct TokenCursorFrame {
+ delim_sp: Option<(Delimiter, DelimSpan)>,
+ tree_cursor: tokenstream::Cursor,
+}
+
+impl TokenCursorFrame {
+ fn new(delim_sp: Option<(Delimiter, DelimSpan)>, tts: TokenStream) -> Self {
+ TokenCursorFrame { delim_sp, tree_cursor: tts.into_trees() }
+ }
+}
+
+impl TokenCursor {
+ fn next(&mut self, desugar_doc_comments: bool) -> (Token, Spacing) {
+ self.inlined_next(desugar_doc_comments)
+ }
+
+ /// This always-inlined version should only be used on hot code paths.
+ #[inline(always)]
+ fn inlined_next(&mut self, desugar_doc_comments: bool) -> (Token, Spacing) {
+ loop {
+ // FIXME: we currently don't return `Delimiter` open/close delims. To fix #67062 we will
+ // need to, whereupon the `delim != Delimiter::Invisible` conditions below can be
+ // removed.
+ if let Some(tree) = self.frame.tree_cursor.next_ref() {
+ match tree {
+ &TokenTree::Token(ref token, spacing) => match (desugar_doc_comments, token) {
+ (true, &Token { kind: token::DocComment(_, attr_style, data), span }) => {
+ return self.desugar(attr_style, data, span);
+ }
+ _ => return (token.clone(), spacing),
+ },
+ &TokenTree::Delimited(sp, delim, ref tts) => {
+ // Set `open_delim` to true here because we deal with it immediately.
+ let frame = TokenCursorFrame::new(Some((delim, sp)), tts.clone());
+ self.stack.push(mem::replace(&mut self.frame, frame));
+ if delim != Delimiter::Invisible {
+ return (Token::new(token::OpenDelim(delim), sp.open), Spacing::Alone);
+ }
+ // No open delimeter to return; continue on to the next iteration.
+ }
+ };
+ } else if let Some(frame) = self.stack.pop() {
+ if let Some((delim, span)) = self.frame.delim_sp && delim != Delimiter::Invisible {
+ self.frame = frame;
+ return (Token::new(token::CloseDelim(delim), span.close), Spacing::Alone);
+ }
+ self.frame = frame;
+ // No close delimiter to return; continue on to the next iteration.
+ } else {
+ return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone);
+ }
+ }
+ }
+
+ fn desugar(&mut self, attr_style: AttrStyle, data: Symbol, span: Span) -> (Token, Spacing) {
+ // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
+ // required to wrap the text.
+ let mut num_of_hashes = 0;
+ let mut count = 0;
+ for ch in data.as_str().chars() {
+ count = match ch {
+ '"' => 1,
+ '#' if count > 0 => count + 1,
+ _ => 0,
+ };
+ num_of_hashes = cmp::max(num_of_hashes, count);
+ }
+
+ let delim_span = DelimSpan::from_single(span);
+ let body = TokenTree::Delimited(
+ delim_span,
+ Delimiter::Bracket,
+ [
+ TokenTree::token_alone(token::Ident(sym::doc, false), span),
+ TokenTree::token_alone(token::Eq, span),
+ TokenTree::token_alone(
+ TokenKind::lit(token::StrRaw(num_of_hashes), data, None),
+ span,
+ ),
+ ]
+ .into_iter()
+ .collect::<TokenStream>(),
+ );
+
+ self.stack.push(mem::replace(
+ &mut self.frame,
+ TokenCursorFrame::new(
+ None,
+ if attr_style == AttrStyle::Inner {
+ [
+ TokenTree::token_alone(token::Pound, span),
+ TokenTree::token_alone(token::Not, span),
+ body,
+ ]
+ .into_iter()
+ .collect::<TokenStream>()
+ } else {
+ [TokenTree::token_alone(token::Pound, span), body]
+ .into_iter()
+ .collect::<TokenStream>()
+ },
+ ),
+ ));
+
+ self.next(/* desugar_doc_comments */ false)
+ }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+enum TokenType {
+ Token(TokenKind),
+ Keyword(Symbol),
+ Operator,
+ Lifetime,
+ Ident,
+ Path,
+ Type,
+ Const,
+}
+
+impl TokenType {
+ fn to_string(&self) -> String {
+ match *self {
+ TokenType::Token(ref t) => format!("`{}`", pprust::token_kind_to_string(t)),
+ TokenType::Keyword(kw) => format!("`{}`", kw),
+ TokenType::Operator => "an operator".to_string(),
+ TokenType::Lifetime => "lifetime".to_string(),
+ TokenType::Ident => "identifier".to_string(),
+ TokenType::Path => "path".to_string(),
+ TokenType::Type => "type".to_string(),
+ TokenType::Const => "a const expression".to_string(),
+ }
+ }
+}
+
+#[derive(Copy, Clone, Debug)]
+enum TokenExpectType {
+ Expect,
+ NoExpect,
+}
+
+/// A sequence separator.
+struct SeqSep {
+ /// The separator token.
+ sep: Option<TokenKind>,
+ /// `true` if a trailing separator is allowed.
+ trailing_sep_allowed: bool,
+}
+
+impl SeqSep {
+ fn trailing_allowed(t: TokenKind) -> SeqSep {
+ SeqSep { sep: Some(t), trailing_sep_allowed: true }
+ }
+
+ fn none() -> SeqSep {
+ SeqSep { sep: None, trailing_sep_allowed: false }
+ }
+}
+
+pub enum FollowedByType {
+ Yes,
+ No,
+}
+
+fn token_descr_opt(token: &Token) -> Option<&'static str> {
+ Some(match token.kind {
+ _ if token.is_special_ident() => "reserved identifier",
+ _ if token.is_used_keyword() => "keyword",
+ _ if token.is_unused_keyword() => "reserved keyword",
+ token::DocComment(..) => "doc comment",
+ _ => return None,
+ })
+}
+
+pub(super) fn token_descr(token: &Token) -> String {
+ let token_str = pprust::token_to_string(token);
+ match token_descr_opt(token) {
+ Some(prefix) => format!("{} `{}`", prefix, token_str),
+ _ => format!("`{}`", token_str),
+ }
+}
+
+impl<'a> Parser<'a> {
+ pub fn new(
+ sess: &'a ParseSess,
+ tokens: TokenStream,
+ desugar_doc_comments: bool,
+ subparser_name: Option<&'static str>,
+ ) -> Self {
+ let mut parser = Parser {
+ sess,
+ token: Token::dummy(),
+ token_spacing: Spacing::Alone,
+ prev_token: Token::dummy(),
+ capture_cfg: false,
+ restrictions: Restrictions::empty(),
+ expected_tokens: Vec::new(),
+ token_cursor: TokenCursor {
+ frame: TokenCursorFrame::new(None, tokens),
+ stack: Vec::new(),
+ num_next_calls: 0,
+ desugar_doc_comments,
+ break_last_token: false,
+ },
+ desugar_doc_comments,
+ unmatched_angle_bracket_count: 0,
+ max_angle_bracket_count: 0,
+ unclosed_delims: Vec::new(),
+ last_unexpected_token_span: None,
+ last_type_ascription: None,
+ subparser_name,
+ capture_state: CaptureState {
+ capturing: Capturing::No,
+ replace_ranges: Vec::new(),
+ inner_attr_ranges: Default::default(),
+ },
+ current_closure: None,
+ };
+
+ // Make parser point to the first token.
+ parser.bump();
+
+ parser
+ }
+
+ pub fn unexpected<T>(&mut self) -> PResult<'a, T> {
+ match self.expect_one_of(&[], &[]) {
+ Err(e) => Err(e),
+ // We can get `Ok(true)` from `recover_closing_delimiter`
+ // which is called in `expected_one_of_not_found`.
+ Ok(_) => FatalError.raise(),
+ }
+ }
+
+ /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
+ pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
+ if self.expected_tokens.is_empty() {
+ if self.token == *t {
+ self.bump();
+ Ok(false)
+ } else {
+ self.unexpected_try_recover(t)
+ }
+ } else {
+ self.expect_one_of(slice::from_ref(t), &[])
+ }
+ }
+
+ /// Expect next token to be edible or inedible token. If edible,
+ /// then consume it; if inedible, then return without consuming
+ /// anything. Signal a fatal error if next token is unexpected.
+ pub fn expect_one_of(
+ &mut self,
+ edible: &[TokenKind],
+ inedible: &[TokenKind],
+ ) -> PResult<'a, bool /* recovered */> {
+ if edible.contains(&self.token.kind) {
+ self.bump();
+ Ok(false)
+ } else if inedible.contains(&self.token.kind) {
+ // leave it in the input
+ Ok(false)
+ } else if self.last_unexpected_token_span == Some(self.token.span) {
+ FatalError.raise();
+ } else {
+ self.expected_one_of_not_found(edible, inedible)
+ }
+ }
+
+ // Public for rustfmt usage.
+ pub fn parse_ident(&mut self) -> PResult<'a, Ident> {
+ self.parse_ident_common(true)
+ }
+
+ fn ident_or_err(&mut self) -> PResult<'a, (Ident, /* is_raw */ bool)> {
+ self.token.ident().ok_or_else(|| match self.prev_token.kind {
+ TokenKind::DocComment(..) => {
+ self.span_err(self.prev_token.span, Error::UselessDocComment)
+ }
+ _ => self.expected_ident_found(),
+ })
+ }
+
+ fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, Ident> {
+ let (ident, is_raw) = self.ident_or_err()?;
+ if !is_raw && ident.is_reserved() {
+ let mut err = self.expected_ident_found();
+ if recover {
+ err.emit();
+ } else {
+ return Err(err);
+ }
+ }
+ self.bump();
+ Ok(ident)
+ }
+
+ /// Checks if the next token is `tok`, and returns `true` if so.
+ ///
+ /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
+ /// encountered.
+ fn check(&mut self, tok: &TokenKind) -> bool {
+ let is_present = self.token == *tok;
+ if !is_present {
+ self.expected_tokens.push(TokenType::Token(tok.clone()));
+ }
+ is_present
+ }
+
+ fn check_noexpect(&self, tok: &TokenKind) -> bool {
+ self.token == *tok
+ }
+
+ /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
+ ///
+ /// the main purpose of this function is to reduce the cluttering of the suggestions list
+ /// which using the normal eat method could introduce in some cases.
+ pub fn eat_noexpect(&mut self, tok: &TokenKind) -> bool {
+ let is_present = self.check_noexpect(tok);
+ if is_present {
+ self.bump()
+ }
+ is_present
+ }
+
+ /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
+ pub fn eat(&mut self, tok: &TokenKind) -> bool {
+ let is_present = self.check(tok);
+ if is_present {
+ self.bump()
+ }
+ is_present
+ }
+
+ /// If the next token is the given keyword, returns `true` without eating it.
+ /// An expectation is also added for diagnostics purposes.
+ fn check_keyword(&mut self, kw: Symbol) -> bool {
+ self.expected_tokens.push(TokenType::Keyword(kw));
+ self.token.is_keyword(kw)
+ }
+
+ /// If the next token is the given keyword, eats it and returns `true`.
+ /// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
+ // Public for rustfmt usage.
+ pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
+ if self.check_keyword(kw) {
+ self.bump();
+ true
+ } else {
+ false
+ }
+ }
+
+ fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
+ if self.token.is_keyword(kw) {
+ self.bump();
+ true
+ } else {
+ false
+ }
+ }
+
+ /// If the given word is not a keyword, signals an error.
+ /// If the next token is not the given word, signals an error.
+ /// Otherwise, eats it.
+ fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
+ if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) }
+ }
+
+ /// Is the given keyword `kw` followed by a non-reserved identifier?
+ fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
+ self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
+ }
+
+ fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
+ if ok {
+ true
+ } else {
+ self.expected_tokens.push(typ);
+ false
+ }
+ }
+
+ fn check_ident(&mut self) -> bool {
+ self.check_or_expected(self.token.is_ident(), TokenType::Ident)
+ }
+
+ fn check_path(&mut self) -> bool {
+ self.check_or_expected(self.token.is_path_start(), TokenType::Path)
+ }
+
+ fn check_type(&mut self) -> bool {
+ self.check_or_expected(self.token.can_begin_type(), TokenType::Type)
+ }
+
+ fn check_const_arg(&mut self) -> bool {
+ self.check_or_expected(self.token.can_begin_const_arg(), TokenType::Const)
+ }
+
+ fn check_inline_const(&self, dist: usize) -> bool {
+ self.is_keyword_ahead(dist, &[kw::Const])
+ && self.look_ahead(dist + 1, |t| match t.kind {
+ token::Interpolated(ref nt) => matches!(**nt, token::NtBlock(..)),
+ token::OpenDelim(Delimiter::Brace) => true,
+ _ => false,
+ })
+ }
+
+ /// Checks to see if the next token is either `+` or `+=`.
+ /// Otherwise returns `false`.
+ fn check_plus(&mut self) -> bool {
+ self.check_or_expected(
+ self.token.is_like_plus(),
+ TokenType::Token(token::BinOp(token::Plus)),
+ )
+ }
+
+ /// Eats the expected token if it's present possibly breaking
+ /// compound tokens like multi-character operators in process.
+ /// Returns `true` if the token was eaten.
+ fn break_and_eat(&mut self, expected: TokenKind) -> bool {
+ if self.token.kind == expected {
+ self.bump();
+ return true;
+ }
+ match self.token.kind.break_two_token_op() {
+ Some((first, second)) if first == expected => {
+ let first_span = self.sess.source_map().start_point(self.token.span);
+ let second_span = self.token.span.with_lo(first_span.hi());
+ self.token = Token::new(first, first_span);
+ // Keep track of this token - if we end token capturing now,
+ // we'll want to append this token to the captured stream.
+ //
+ // If we consume any additional tokens, then this token
+ // is not needed (we'll capture the entire 'glued' token),
+ // and `bump` will set this field to `None`
+ self.token_cursor.break_last_token = true;
+ // Use the spacing of the glued token as the spacing
+ // of the unglued second token.
+ self.bump_with((Token::new(second, second_span), self.token_spacing));
+ true
+ }
+ _ => {
+ self.expected_tokens.push(TokenType::Token(expected));
+ false
+ }
+ }
+ }
+
+ /// Eats `+` possibly breaking tokens like `+=` in process.
+ fn eat_plus(&mut self) -> bool {
+ self.break_and_eat(token::BinOp(token::Plus))
+ }
+
+ /// Eats `&` possibly breaking tokens like `&&` in process.
+ /// Signals an error if `&` is not eaten.
+ fn expect_and(&mut self) -> PResult<'a, ()> {
+ if self.break_and_eat(token::BinOp(token::And)) { Ok(()) } else { self.unexpected() }
+ }
+
+ /// Eats `|` possibly breaking tokens like `||` in process.
+ /// Signals an error if `|` was not eaten.
+ fn expect_or(&mut self) -> PResult<'a, ()> {
+ if self.break_and_eat(token::BinOp(token::Or)) { Ok(()) } else { self.unexpected() }
+ }
+
+ /// Eats `<` possibly breaking tokens like `<<` in process.
+ fn eat_lt(&mut self) -> bool {
+ let ate = self.break_and_eat(token::Lt);
+ if ate {
+ // See doc comment for `unmatched_angle_bracket_count`.
+ self.unmatched_angle_bracket_count += 1;
+ self.max_angle_bracket_count += 1;
+ debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
+ }
+ ate
+ }
+
+ /// Eats `<` possibly breaking tokens like `<<` in process.
+ /// Signals an error if `<` was not eaten.
+ fn expect_lt(&mut self) -> PResult<'a, ()> {
+ if self.eat_lt() { Ok(()) } else { self.unexpected() }
+ }
+
+ /// Eats `>` possibly breaking tokens like `>>` in process.
+ /// Signals an error if `>` was not eaten.
+ fn expect_gt(&mut self) -> PResult<'a, ()> {
+ if self.break_and_eat(token::Gt) {
+ // See doc comment for `unmatched_angle_bracket_count`.
+ if self.unmatched_angle_bracket_count > 0 {
+ self.unmatched_angle_bracket_count -= 1;
+ debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
+ }
+ Ok(())
+ } else {
+ self.unexpected()
+ }
+ }
+
+ fn expect_any_with_type(&mut self, kets: &[&TokenKind], expect: TokenExpectType) -> bool {
+ kets.iter().any(|k| match expect {
+ TokenExpectType::Expect => self.check(k),
+ TokenExpectType::NoExpect => self.token == **k,
+ })
+ }
+
+ fn parse_seq_to_before_tokens<T>(
+ &mut self,
+ kets: &[&TokenKind],
+ sep: SeqSep,
+ expect: TokenExpectType,
+ mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool /* trailing */, bool /* recovered */)> {
+ let mut first = true;
+ let mut recovered = false;
+ let mut trailing = false;
+ let mut v = vec![];
+ let unclosed_delims = !self.unclosed_delims.is_empty();
+
+ while !self.expect_any_with_type(kets, expect) {
+ if let token::CloseDelim(..) | token::Eof = self.token.kind {
+ break;
+ }
+ if let Some(ref t) = sep.sep {
+ if first {
+ first = false;
+ } else {
+ match self.expect(t) {
+ Ok(false) => {
+ self.current_closure.take();
+ }
+ Ok(true) => {
+ self.current_closure.take();
+ recovered = true;
+ break;
+ }
+ Err(mut expect_err) => {
+ let sp = self.prev_token.span.shrink_to_hi();
+ let token_str = pprust::token_kind_to_string(t);
+
+ match self.current_closure.take() {
+ Some(closure_spans) if self.token.kind == TokenKind::Semi => {
+ // Finding a semicolon instead of a comma
+ // after a closure body indicates that the
+ // closure body may be a block but the user
+ // forgot to put braces around its
+ // statements.
+
+ self.recover_missing_braces_around_closure_body(
+ closure_spans,
+ expect_err,
+ )?;
+
+ continue;
+ }
+
+ _ => {
+ // Attempt to keep parsing if it was a similar separator.
+ if let Some(ref tokens) = t.similar_tokens() {
+ if tokens.contains(&self.token.kind) && !unclosed_delims {
+ self.bump();
+ }
+ }
+ }
+ }
+
+ // If this was a missing `@` in a binding pattern
+ // bail with a suggestion
+ // https://github.com/rust-lang/rust/issues/72373
+ if self.prev_token.is_ident() && self.token.kind == token::DotDot {
+ let msg = format!(
+ "if you meant to bind the contents of \
+ the rest of the array pattern into `{}`, use `@`",
+ pprust::token_to_string(&self.prev_token)
+ );
+ expect_err
+ .span_suggestion_verbose(
+ self.prev_token.span.shrink_to_hi().until(self.token.span),
+ &msg,
+ " @ ",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ break;
+ }
+
+ // Attempt to keep parsing if it was an omitted separator.
+ match f(self) {
+ Ok(t) => {
+ // Parsed successfully, therefore most probably the code only
+ // misses a separator.
+ expect_err
+ .span_suggestion_short(
+ sp,
+ &format!("missing `{}`", token_str),
+ token_str,
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+
+ v.push(t);
+ continue;
+ }
+ Err(e) => {
+ // Parsing failed, therefore it must be something more serious
+ // than just a missing separator.
+ expect_err.emit();
+
+ e.cancel();
+ break;
+ }
+ }
+ }
+ }
+ }
+ }
+ if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) {
+ trailing = true;
+ break;
+ }
+
+ let t = f(self)?;
+ v.push(t);
+ }
+
+ Ok((v, trailing, recovered))
+ }
+
+ fn recover_missing_braces_around_closure_body(
+ &mut self,
+ closure_spans: ClosureSpans,
+ mut expect_err: DiagnosticBuilder<'_, ErrorGuaranteed>,
+ ) -> PResult<'a, ()> {
+ let initial_semicolon = self.token.span;
+
+ while self.eat(&TokenKind::Semi) {
+ let _ = self.parse_stmt(ForceCollect::Yes)?;
+ }
+
+ expect_err.set_primary_message(
+ "closure bodies that contain statements must be surrounded by braces",
+ );
+
+ let preceding_pipe_span = closure_spans.closing_pipe;
+ let following_token_span = self.token.span;
+
+ let mut first_note = MultiSpan::from(vec![initial_semicolon]);
+ first_note.push_span_label(
+ initial_semicolon,
+ "this `;` turns the preceding closure into a statement",
+ );
+ first_note.push_span_label(
+ closure_spans.body,
+ "this expression is a statement because of the trailing semicolon",
+ );
+ expect_err.span_note(first_note, "statement found outside of a block");
+
+ let mut second_note = MultiSpan::from(vec![closure_spans.whole_closure]);
+ second_note.push_span_label(closure_spans.whole_closure, "this is the parsed closure...");
+ second_note.push_span_label(
+ following_token_span,
+ "...but likely you meant the closure to end here",
+ );
+ expect_err.span_note(second_note, "the closure body may be incorrectly delimited");
+
+ expect_err.set_span(vec![preceding_pipe_span, following_token_span]);
+
+ let opening_suggestion_str = " {".to_string();
+ let closing_suggestion_str = "}".to_string();
+
+ expect_err.multipart_suggestion(
+ "try adding braces",
+ vec![
+ (preceding_pipe_span.shrink_to_hi(), opening_suggestion_str),
+ (following_token_span.shrink_to_lo(), closing_suggestion_str),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+
+ expect_err.emit();
+
+ Ok(())
+ }
+
+ /// Parses a sequence, not including the closing delimiter. The function
+ /// `f` must consume tokens until reaching the next separator or
+ /// closing bracket.
+ fn parse_seq_to_before_end<T>(
+ &mut self,
+ ket: &TokenKind,
+ sep: SeqSep,
+ f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool, bool)> {
+ self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
+ }
+
+ /// Parses a sequence, including the closing delimiter. The function
+ /// `f` must consume tokens until reaching the next separator or
+ /// closing bracket.
+ fn parse_seq_to_end<T>(
+ &mut self,
+ ket: &TokenKind,
+ sep: SeqSep,
+ f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool /* trailing */)> {
+ let (val, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+ if !recovered {
+ self.eat(ket);
+ }
+ Ok((val, trailing))
+ }
+
+ /// Parses a sequence, including the closing delimiter. The function
+ /// `f` must consume tokens until reaching the next separator or
+ /// closing bracket.
+ fn parse_unspanned_seq<T>(
+ &mut self,
+ bra: &TokenKind,
+ ket: &TokenKind,
+ sep: SeqSep,
+ f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool)> {
+ self.expect(bra)?;
+ self.parse_seq_to_end(ket, sep, f)
+ }
+
+ fn parse_delim_comma_seq<T>(
+ &mut self,
+ delim: Delimiter,
+ f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool)> {
+ self.parse_unspanned_seq(
+ &token::OpenDelim(delim),
+ &token::CloseDelim(delim),
+ SeqSep::trailing_allowed(token::Comma),
+ f,
+ )
+ }
+
+ fn parse_paren_comma_seq<T>(
+ &mut self,
+ f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+ ) -> PResult<'a, (Vec<T>, bool)> {
+ self.parse_delim_comma_seq(Delimiter::Parenthesis, f)
+ }
+
+ /// Advance the parser by one token using provided token as the next one.
+ fn bump_with(&mut self, next: (Token, Spacing)) {
+ self.inlined_bump_with(next)
+ }
+
+ /// This always-inlined version should only be used on hot code paths.
+ #[inline(always)]
+ fn inlined_bump_with(&mut self, (next_token, next_spacing): (Token, Spacing)) {
+ // Update the current and previous tokens.
+ self.prev_token = mem::replace(&mut self.token, next_token);
+ self.token_spacing = next_spacing;
+
+ // Diagnostics.
+ self.expected_tokens.clear();
+ }
+
+ /// Advance the parser by one token.
+ pub fn bump(&mut self) {
+ // Note: destructuring here would give nicer code, but it was found in #96210 to be slower
+ // than `.0`/`.1` access.
+ let mut next = self.token_cursor.inlined_next(self.desugar_doc_comments);
+ self.token_cursor.num_next_calls += 1;
+ // We've retrieved an token from the underlying
+ // cursor, so we no longer need to worry about
+ // an unglued token. See `break_and_eat` for more details
+ self.token_cursor.break_last_token = false;
+ if next.0.span.is_dummy() {
+ // Tweak the location for better diagnostics, but keep syntactic context intact.
+ let fallback_span = self.token.span;
+ next.0.span = fallback_span.with_ctxt(next.0.span.ctxt());
+ }
+ debug_assert!(!matches!(
+ next.0.kind,
+ token::OpenDelim(Delimiter::Invisible) | token::CloseDelim(Delimiter::Invisible)
+ ));
+ self.inlined_bump_with(next)
+ }
+
+ /// Look-ahead `dist` tokens of `self.token` and get access to that token there.
+ /// When `dist == 0` then the current token is looked at.
+ pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R {
+ if dist == 0 {
+ return looker(&self.token);
+ }
+
+ let frame = &self.token_cursor.frame;
+ if let Some((delim, span)) = frame.delim_sp && delim != Delimiter::Invisible {
+ let all_normal = (0..dist).all(|i| {
+ let token = frame.tree_cursor.look_ahead(i);
+ !matches!(token, Some(TokenTree::Delimited(_, Delimiter::Invisible, _)))
+ });
+ if all_normal {
+ return match frame.tree_cursor.look_ahead(dist - 1) {
+ Some(tree) => match tree {
+ TokenTree::Token(token, _) => looker(token),
+ TokenTree::Delimited(dspan, delim, _) => {
+ looker(&Token::new(token::OpenDelim(*delim), dspan.open))
+ }
+ },
+ None => looker(&Token::new(token::CloseDelim(delim), span.close)),
+ };
+ }
+ }
+
+ let mut cursor = self.token_cursor.clone();
+ let mut i = 0;
+ let mut token = Token::dummy();
+ while i < dist {
+ token = cursor.next(/* desugar_doc_comments */ false).0;
+ if matches!(
+ token.kind,
+ token::OpenDelim(Delimiter::Invisible) | token::CloseDelim(Delimiter::Invisible)
+ ) {
+ continue;
+ }
+ i += 1;
+ }
+ return looker(&token);
+ }
+
+ /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
+ fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
+ self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
+ }
+
+ /// Parses asyncness: `async` or nothing.
+ fn parse_asyncness(&mut self) -> Async {
+ if self.eat_keyword(kw::Async) {
+ let span = self.prev_token.uninterpolated_span();
+ Async::Yes { span, closure_id: DUMMY_NODE_ID, return_impl_trait_id: DUMMY_NODE_ID }
+ } else {
+ Async::No
+ }
+ }
+
+ /// Parses unsafety: `unsafe` or nothing.
+ fn parse_unsafety(&mut self) -> Unsafe {
+ if self.eat_keyword(kw::Unsafe) {
+ Unsafe::Yes(self.prev_token.uninterpolated_span())
+ } else {
+ Unsafe::No
+ }
+ }
+
+ /// Parses constness: `const` or nothing.
+ fn parse_constness(&mut self) -> Const {
+ // Avoid const blocks to be parsed as const items
+ if self.look_ahead(1, |t| t != &token::OpenDelim(Delimiter::Brace))
+ && self.eat_keyword(kw::Const)
+ {
+ Const::Yes(self.prev_token.uninterpolated_span())
+ } else {
+ Const::No
+ }
+ }
+
+ /// Parses inline const expressions.
+ fn parse_const_block(&mut self, span: Span, pat: bool) -> PResult<'a, P<Expr>> {
+ if pat {
+ self.sess.gated_spans.gate(sym::inline_const_pat, span);
+ } else {
+ self.sess.gated_spans.gate(sym::inline_const, span);
+ }
+ self.eat_keyword(kw::Const);
+ let (attrs, blk) = self.parse_inner_attrs_and_block()?;
+ let anon_const = AnonConst {
+ id: DUMMY_NODE_ID,
+ value: self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()),
+ };
+ let blk_span = anon_const.value.span;
+ Ok(self.mk_expr(span.to(blk_span), ExprKind::ConstBlock(anon_const), AttrVec::from(attrs)))
+ }
+
+ /// Parses mutability (`mut` or nothing).
+ fn parse_mutability(&mut self) -> Mutability {
+ if self.eat_keyword(kw::Mut) { Mutability::Mut } else { Mutability::Not }
+ }
+
+ /// Possibly parses mutability (`const` or `mut`).
+ fn parse_const_or_mut(&mut self) -> Option<Mutability> {
+ if self.eat_keyword(kw::Mut) {
+ Some(Mutability::Mut)
+ } else if self.eat_keyword(kw::Const) {
+ Some(Mutability::Not)
+ } else {
+ None
+ }
+ }
+
+ fn parse_field_name(&mut self) -> PResult<'a, Ident> {
+ if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token.kind
+ {
+ self.expect_no_suffix(self.token.span, "a tuple index", suffix);
+ self.bump();
+ Ok(Ident::new(symbol, self.prev_token.span))
+ } else {
+ self.parse_ident_common(true)
+ }
+ }
+
+ fn parse_mac_args(&mut self) -> PResult<'a, P<MacArgs>> {
+ self.parse_mac_args_common(true).map(P)
+ }
+
+ fn parse_attr_args(&mut self) -> PResult<'a, MacArgs> {
+ self.parse_mac_args_common(false)
+ }
+
+ fn parse_mac_args_common(&mut self, delimited_only: bool) -> PResult<'a, MacArgs> {
+ Ok(
+ if self.check(&token::OpenDelim(Delimiter::Parenthesis))
+ || self.check(&token::OpenDelim(Delimiter::Bracket))
+ || self.check(&token::OpenDelim(Delimiter::Brace))
+ {
+ match self.parse_token_tree() {
+ TokenTree::Delimited(dspan, delim, tokens) =>
+ // We've confirmed above that there is a delimiter so unwrapping is OK.
+ {
+ MacArgs::Delimited(dspan, MacDelimiter::from_token(delim).unwrap(), tokens)
+ }
+ _ => unreachable!(),
+ }
+ } else if !delimited_only {
+ if self.eat(&token::Eq) {
+ let eq_span = self.prev_token.span;
+ MacArgs::Eq(eq_span, MacArgsEq::Ast(self.parse_expr_force_collect()?))
+ } else {
+ MacArgs::Empty
+ }
+ } else {
+ return self.unexpected();
+ },
+ )
+ }
+
+ fn parse_or_use_outer_attributes(
+ &mut self,
+ already_parsed_attrs: Option<AttrWrapper>,
+ ) -> PResult<'a, AttrWrapper> {
+ if let Some(attrs) = already_parsed_attrs {
+ Ok(attrs)
+ } else {
+ self.parse_outer_attributes()
+ }
+ }
+
+ /// Parses a single token tree from the input.
+ pub(crate) fn parse_token_tree(&mut self) -> TokenTree {
+ match self.token.kind {
+ token::OpenDelim(..) => {
+ // Grab the tokens from this frame.
+ let frame = &self.token_cursor.frame;
+ let stream = frame.tree_cursor.stream.clone();
+ let (delim, span) = frame.delim_sp.unwrap();
+
+ // Advance the token cursor through the entire delimited
+ // sequence. After getting the `OpenDelim` we are *within* the
+ // delimited sequence, i.e. at depth `d`. After getting the
+ // matching `CloseDelim` we are *after* the delimited sequence,
+ // i.e. at depth `d - 1`.
+ let target_depth = self.token_cursor.stack.len() - 1;
+ loop {
+ // Advance one token at a time, so `TokenCursor::next()`
+ // can capture these tokens if necessary.
+ self.bump();
+ if self.token_cursor.stack.len() == target_depth {
+ debug_assert!(matches!(self.token.kind, token::CloseDelim(_)));
+ break;
+ }
+ }
+
+ // Consume close delimiter
+ self.bump();
+ TokenTree::Delimited(span, delim, stream)
+ }
+ token::CloseDelim(_) | token::Eof => unreachable!(),
+ _ => {
+ self.bump();
+ TokenTree::Token(self.prev_token.clone(), Spacing::Alone)
+ }
+ }
+ }
+
+ /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
+ pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
+ let mut tts = Vec::new();
+ while self.token != token::Eof {
+ tts.push(self.parse_token_tree());
+ }
+ Ok(tts)
+ }
+
+ pub fn parse_tokens(&mut self) -> TokenStream {
+ let mut result = Vec::new();
+ loop {
+ match self.token.kind {
+ token::Eof | token::CloseDelim(..) => break,
+ _ => result.push(self.parse_token_tree()),
+ }
+ }
+ TokenStream::new(result)
+ }
+
+ /// Evaluates the closure with restrictions in place.
+ ///
+ /// Afters the closure is evaluated, restrictions are reset.
+ fn with_res<T>(&mut self, res: Restrictions, f: impl FnOnce(&mut Self) -> T) -> T {
+ let old = self.restrictions;
+ self.restrictions = res;
+ let res = f(self);
+ self.restrictions = old;
+ res
+ }
+
+ /// Parses `pub` and `pub(in path)` plus shortcuts `pub(crate)` for `pub(in crate)`, `pub(self)`
+ /// for `pub(in self)` and `pub(super)` for `pub(in super)`.
+ /// If the following element can't be a tuple (i.e., it's a function definition), then
+ /// it's not a tuple struct field), and the contents within the parentheses aren't valid,
+ /// so emit a proper diagnostic.
+ // Public for rustfmt usage.
+ pub fn parse_visibility(&mut self, fbt: FollowedByType) -> PResult<'a, Visibility> {
+ maybe_whole!(self, NtVis, |x| x.into_inner());
+
+ if !self.eat_keyword(kw::Pub) {
+ // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
+ // keyword to grab a span from for inherited visibility; an empty span at the
+ // beginning of the current token would seem to be the "Schelling span".
+ return Ok(Visibility {
+ span: self.token.span.shrink_to_lo(),
+ kind: VisibilityKind::Inherited,
+ tokens: None,
+ });
+ }
+ let lo = self.prev_token.span;
+
+ if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ // We don't `self.bump()` the `(` yet because this might be a struct definition where
+ // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
+ // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
+ // by the following tokens.
+ if self.is_keyword_ahead(1, &[kw::In]) {
+ // Parse `pub(in path)`.
+ self.bump(); // `(`
+ self.bump(); // `in`
+ let path = self.parse_path(PathStyle::Mod)?; // `path`
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+ let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
+ return Ok(Visibility {
+ span: lo.to(self.prev_token.span),
+ kind: vis,
+ tokens: None,
+ });
+ } else if self.look_ahead(2, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
+ && self.is_keyword_ahead(1, &[kw::Crate, kw::Super, kw::SelfLower])
+ {
+ // Parse `pub(crate)`, `pub(self)`, or `pub(super)`.
+ self.bump(); // `(`
+ let path = self.parse_path(PathStyle::Mod)?; // `crate`/`super`/`self`
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+ let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
+ return Ok(Visibility {
+ span: lo.to(self.prev_token.span),
+ kind: vis,
+ tokens: None,
+ });
+ } else if let FollowedByType::No = fbt {
+ // Provide this diagnostic if a type cannot follow;
+ // in particular, if this is not a tuple struct.
+ self.recover_incorrect_vis_restriction()?;
+ // Emit diagnostic, but continue with public visibility.
+ }
+ }
+
+ Ok(Visibility { span: lo, kind: VisibilityKind::Public, tokens: None })
+ }
+
+ /// Recovery for e.g. `pub(something) fn ...` or `struct X { pub(something) y: Z }`
+ fn recover_incorrect_vis_restriction(&mut self) -> PResult<'a, ()> {
+ self.bump(); // `(`
+ let path = self.parse_path(PathStyle::Mod)?;
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+
+ let msg = "incorrect visibility restriction";
+ let suggestion = r##"some possible visibility restrictions are:
+`pub(crate)`: visible only on the current crate
+`pub(super)`: visible only in the current module's parent
+`pub(in path::to::module)`: visible only on the specified path"##;
+
+ let path_str = pprust::path_to_string(&path);
+
+ struct_span_err!(self.sess.span_diagnostic, path.span, E0704, "{}", msg)
+ .help(suggestion)
+ .span_suggestion(
+ path.span,
+ &format!("make this visible only to module `{}` with `in`", path_str),
+ format!("in {}", path_str),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ Ok(())
+ }
+
+ /// Parses `extern string_literal?`.
+ fn parse_extern(&mut self) -> Extern {
+ if self.eat_keyword(kw::Extern) {
+ let mut extern_span = self.prev_token.span;
+ let abi = self.parse_abi();
+ if let Some(abi) = abi {
+ extern_span = extern_span.to(abi.span);
+ }
+ Extern::from_abi(abi, extern_span)
+ } else {
+ Extern::None
+ }
+ }
+
+ /// Parses a string literal as an ABI spec.
+ fn parse_abi(&mut self) -> Option<StrLit> {
+ match self.parse_str_lit() {
+ Ok(str_lit) => Some(str_lit),
+ Err(Some(lit)) => match lit.kind {
+ ast::LitKind::Err(_) => None,
+ _ => {
+ self.struct_span_err(lit.span, "non-string ABI literal")
+ .span_suggestion(
+ lit.span,
+ "specify the ABI with a string literal",
+ "\"C\"",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ None
+ }
+ },
+ Err(None) => None,
+ }
+ }
+
+ pub fn collect_tokens_no_attrs<R: HasAttrs + HasTokens>(
+ &mut self,
+ f: impl FnOnce(&mut Self) -> PResult<'a, R>,
+ ) -> PResult<'a, R> {
+ // The only reason to call `collect_tokens_no_attrs` is if you want tokens, so use
+ // `ForceCollect::Yes`
+ self.collect_tokens_trailing_token(
+ AttrWrapper::empty(),
+ ForceCollect::Yes,
+ |this, _attrs| Ok((f(this)?, TrailingToken::None)),
+ )
+ }
+
+ /// `::{` or `::*`
+ fn is_import_coupler(&mut self) -> bool {
+ self.check(&token::ModSep)
+ && self.look_ahead(1, |t| {
+ *t == token::OpenDelim(Delimiter::Brace) || *t == token::BinOp(token::Star)
+ })
+ }
+
+ pub fn clear_expected_tokens(&mut self) {
+ self.expected_tokens.clear();
+ }
+}
+
+pub(crate) fn make_unclosed_delims_error(
+ unmatched: UnmatchedBrace,
+ sess: &ParseSess,
+) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> {
+ // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
+ // `unmatched_braces` only for error recovery in the `Parser`.
+ let found_delim = unmatched.found_delim?;
+ let span: MultiSpan = if let Some(sp) = unmatched.unclosed_span {
+ vec![unmatched.found_span, sp].into()
+ } else {
+ unmatched.found_span.into()
+ };
+ let mut err = sess.span_diagnostic.struct_span_err(
+ span,
+ &format!(
+ "mismatched closing delimiter: `{}`",
+ pprust::token_kind_to_string(&token::CloseDelim(found_delim)),
+ ),
+ );
+ err.span_label(unmatched.found_span, "mismatched closing delimiter");
+ if let Some(sp) = unmatched.candidate_span {
+ err.span_label(sp, "closing delimiter possibly meant for this");
+ }
+ if let Some(sp) = unmatched.unclosed_span {
+ err.span_label(sp, "unclosed delimiter");
+ }
+ Some(err)
+}
+
+pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, sess: &ParseSess) {
+ *sess.reached_eof.borrow_mut() |=
+ unclosed_delims.iter().any(|unmatched_delim| unmatched_delim.found_delim.is_none());
+ for unmatched in unclosed_delims.drain(..) {
+ if let Some(mut e) = make_unclosed_delims_error(unmatched, sess) {
+ e.emit();
+ }
+ }
+}
+
+/// A helper struct used when building an `AttrAnnotatedTokenStream` from
+/// a `LazyTokenStream`. Both delimiter and non-delimited tokens
+/// are stored as `FlatToken::Token`. A vector of `FlatToken`s
+/// is then 'parsed' to build up an `AttrAnnotatedTokenStream` with nested
+/// `AttrAnnotatedTokenTree::Delimited` tokens
+#[derive(Debug, Clone)]
+pub enum FlatToken {
+ /// A token - this holds both delimiter (e.g. '{' and '}')
+ /// and non-delimiter tokens
+ Token(Token),
+ /// Holds the `AttributesData` for an AST node. The
+ /// `AttributesData` is inserted directly into the
+ /// constructed `AttrAnnotatedTokenStream` as
+ /// an `AttrAnnotatedTokenTree::Attributes`
+ AttrTarget(AttributesData),
+ /// A special 'empty' token that is ignored during the conversion
+ /// to an `AttrAnnotatedTokenStream`. This is used to simplify the
+ /// handling of replace ranges.
+ Empty,
+}
+
+#[derive(Debug)]
+pub enum NtOrTt {
+ Nt(Nonterminal),
+ Tt(TokenTree),
+}
diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs
new file mode 100644
index 000000000..e215b6872
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/nonterminal.rs
@@ -0,0 +1,203 @@
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, NonterminalKind, Token};
+use rustc_ast::HasTokens;
+use rustc_ast_pretty::pprust;
+use rustc_errors::PResult;
+use rustc_span::symbol::{kw, Ident};
+
+use crate::parser::pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
+use crate::parser::{FollowedByType, ForceCollect, NtOrTt, Parser, PathStyle};
+
+impl<'a> Parser<'a> {
+ /// Checks whether a non-terminal may begin with a particular token.
+ ///
+ /// Returning `false` is a *stability guarantee* that such a matcher will *never* begin with
+ /// that token. Be conservative (return true) if not sure. Inlined because it has a single call
+ /// site.
+ #[inline]
+ pub fn nonterminal_may_begin_with(kind: NonterminalKind, token: &Token) -> bool {
+ /// Checks whether the non-terminal may contain a single (non-keyword) identifier.
+ fn may_be_ident(nt: &token::Nonterminal) -> bool {
+ match *nt {
+ token::NtItem(_) | token::NtBlock(_) | token::NtVis(_) | token::NtLifetime(_) => {
+ false
+ }
+ _ => true,
+ }
+ }
+
+ match kind {
+ NonterminalKind::Expr => {
+ token.can_begin_expr()
+ // This exception is here for backwards compatibility.
+ && !token.is_keyword(kw::Let)
+ // This exception is here for backwards compatibility.
+ && !token.is_keyword(kw::Const)
+ }
+ NonterminalKind::Ty => token.can_begin_type(),
+ NonterminalKind::Ident => get_macro_ident(token).is_some(),
+ NonterminalKind::Literal => token.can_begin_literal_maybe_minus(),
+ NonterminalKind::Vis => match token.kind {
+ // The follow-set of :vis + "priv" keyword + interpolated
+ token::Comma | token::Ident(..) | token::Interpolated(..) => true,
+ _ => token.can_begin_type(),
+ },
+ NonterminalKind::Block => match token.kind {
+ token::OpenDelim(Delimiter::Brace) => true,
+ token::Interpolated(ref nt) => !matches!(
+ **nt,
+ token::NtItem(_)
+ | token::NtPat(_)
+ | token::NtTy(_)
+ | token::NtIdent(..)
+ | token::NtMeta(_)
+ | token::NtPath(_)
+ | token::NtVis(_)
+ ),
+ _ => false,
+ },
+ NonterminalKind::Path | NonterminalKind::Meta => match token.kind {
+ token::ModSep | token::Ident(..) => true,
+ token::Interpolated(ref nt) => match **nt {
+ token::NtPath(_) | token::NtMeta(_) => true,
+ _ => may_be_ident(&nt),
+ },
+ _ => false,
+ },
+ NonterminalKind::PatParam { .. } | NonterminalKind::PatWithOr { .. } => {
+ match token.kind {
+ token::Ident(..) | // box, ref, mut, and other identifiers (can stricten)
+ token::OpenDelim(Delimiter::Parenthesis) | // tuple pattern
+ token::OpenDelim(Delimiter::Bracket) | // slice pattern
+ token::BinOp(token::And) | // reference
+ token::BinOp(token::Minus) | // negative literal
+ token::AndAnd | // double reference
+ token::Literal(..) | // literal
+ token::DotDot | // range pattern (future compat)
+ token::DotDotDot | // range pattern (future compat)
+ token::ModSep | // path
+ token::Lt | // path (UFCS constant)
+ token::BinOp(token::Shl) => true, // path (double UFCS)
+ // leading vert `|` or-pattern
+ token::BinOp(token::Or) => matches!(kind, NonterminalKind::PatWithOr {..}),
+ token::Interpolated(ref nt) => may_be_ident(nt),
+ _ => false,
+ }
+ }
+ NonterminalKind::Lifetime => match token.kind {
+ token::Lifetime(_) => true,
+ token::Interpolated(ref nt) => {
+ matches!(**nt, token::NtLifetime(_))
+ }
+ _ => false,
+ },
+ NonterminalKind::TT | NonterminalKind::Item | NonterminalKind::Stmt => {
+ !matches!(token.kind, token::CloseDelim(_))
+ }
+ }
+ }
+
+ /// Parse a non-terminal (e.g. MBE `:pat` or `:ident`). Inlined because there is only one call
+ /// site.
+ #[inline]
+ pub fn parse_nonterminal(&mut self, kind: NonterminalKind) -> PResult<'a, NtOrTt> {
+ // Any `Nonterminal` which stores its tokens (currently `NtItem` and `NtExpr`)
+ // needs to have them force-captured here.
+ // A `macro_rules!` invocation may pass a captured item/expr to a proc-macro,
+ // which requires having captured tokens available. Since we cannot determine
+ // in advance whether or not a proc-macro will be (transitively) invoked,
+ // we always capture tokens for any `Nonterminal` which needs them.
+ let mut nt = match kind {
+ // Note that TT is treated differently to all the others.
+ NonterminalKind::TT => return Ok(NtOrTt::Tt(self.parse_token_tree())),
+ NonterminalKind::Item => match self.parse_item(ForceCollect::Yes)? {
+ Some(item) => token::NtItem(item),
+ None => {
+ return Err(self.struct_span_err(self.token.span, "expected an item keyword"));
+ }
+ },
+ NonterminalKind::Block => {
+ // While a block *expression* may have attributes (e.g. `#[my_attr] { ... }`),
+ // the ':block' matcher does not support them
+ token::NtBlock(self.collect_tokens_no_attrs(|this| this.parse_block())?)
+ }
+ NonterminalKind::Stmt => match self.parse_stmt(ForceCollect::Yes)? {
+ Some(s) => token::NtStmt(P(s)),
+ None => {
+ return Err(self.struct_span_err(self.token.span, "expected a statement"));
+ }
+ },
+ NonterminalKind::PatParam { .. } | NonterminalKind::PatWithOr { .. } => {
+ token::NtPat(self.collect_tokens_no_attrs(|this| match kind {
+ NonterminalKind::PatParam { .. } => this.parse_pat_no_top_alt(None),
+ NonterminalKind::PatWithOr { .. } => this.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::No,
+ RecoverColon::No,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ ),
+ _ => unreachable!(),
+ })?)
+ }
+
+ NonterminalKind::Expr => token::NtExpr(self.parse_expr_force_collect()?),
+ NonterminalKind::Literal => {
+ // The `:literal` matcher does not support attributes
+ token::NtLiteral(
+ self.collect_tokens_no_attrs(|this| this.parse_literal_maybe_minus())?,
+ )
+ }
+
+ NonterminalKind::Ty => token::NtTy(
+ self.collect_tokens_no_attrs(|this| this.parse_no_question_mark_recover())?,
+ ),
+
+ // this could be handled like a token, since it is one
+ NonterminalKind::Ident
+ if let Some((ident, is_raw)) = get_macro_ident(&self.token) =>
+ {
+ self.bump();
+ token::NtIdent(ident, is_raw)
+ }
+ NonterminalKind::Ident => {
+ let token_str = pprust::token_to_string(&self.token);
+ let msg = &format!("expected ident, found {}", &token_str);
+ return Err(self.struct_span_err(self.token.span, msg));
+ }
+ NonterminalKind::Path => token::NtPath(
+ P(self.collect_tokens_no_attrs(|this| this.parse_path(PathStyle::Type))?),
+ ),
+ NonterminalKind::Meta => token::NtMeta(P(self.parse_attr_item(true)?)),
+ NonterminalKind::Vis => token::NtVis(
+ P(self.collect_tokens_no_attrs(|this| this.parse_visibility(FollowedByType::Yes))?),
+ ),
+ NonterminalKind::Lifetime => {
+ if self.check_lifetime() {
+ token::NtLifetime(self.expect_lifetime().ident)
+ } else {
+ let token_str = pprust::token_to_string(&self.token);
+ let msg = &format!("expected a lifetime, found `{}`", &token_str);
+ return Err(self.struct_span_err(self.token.span, msg));
+ }
+ }
+ };
+
+ // If tokens are supported at all, they should be collected.
+ if matches!(nt.tokens_mut(), Some(None)) {
+ panic!(
+ "Missing tokens for nt {:?} at {:?}: {:?}",
+ nt,
+ nt.span(),
+ pprust::nonterminal_to_string(&nt)
+ );
+ }
+
+ Ok(NtOrTt::Nt(nt))
+ }
+}
+
+/// The token is an identifier, but not `_`.
+/// We prohibit passing `_` to macros expecting `ident` for now.
+fn get_macro_ident(token: &Token) -> Option<(Ident, bool)> {
+ token.ident().filter(|(ident, _)| ident.name != kw::Underscore)
+}
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
new file mode 100644
index 000000000..ba77a3958
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -0,0 +1,1151 @@
+use super::{ForceCollect, Parser, PathStyle, TrailingToken};
+use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+use rustc_ast::mut_visit::{noop_visit_pat, MutVisitor};
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter};
+use rustc_ast::{
+ self as ast, AttrVec, Attribute, BindingMode, Expr, ExprKind, MacCall, Mutability, Pat,
+ PatField, PatKind, Path, QSelf, RangeEnd, RangeSyntax,
+};
+use rustc_ast_pretty::pprust;
+use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
+use rustc_span::source_map::{respan, Span, Spanned};
+use rustc_span::symbol::{kw, sym, Ident};
+
+pub(super) type Expected = Option<&'static str>;
+
+/// `Expected` for function and lambda parameter patterns.
+pub(super) const PARAM_EXPECTED: Expected = Some("parameter name");
+
+const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here";
+
+/// Whether or not to recover a `,` when parsing or-patterns.
+#[derive(PartialEq, Copy, Clone)]
+pub enum RecoverComma {
+ Yes,
+ No,
+}
+
+/// Whether or not to recover a `:` when parsing patterns that were meant to be paths.
+#[derive(PartialEq, Copy, Clone)]
+pub enum RecoverColon {
+ Yes,
+ No,
+}
+
+/// Whether or not to recover a `a, b` when parsing patterns as `(a, b)` or that *and* `a | b`.
+#[derive(PartialEq, Copy, Clone)]
+pub enum CommaRecoveryMode {
+ LikelyTuple,
+ EitherTupleOrPipe,
+}
+
+/// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid
+/// emitting duplicate diagnostics.
+#[derive(Debug, Clone, Copy)]
+enum EatOrResult {
+ /// We recovered from a trailing vert.
+ TrailingVert,
+ /// We ate an `|` (or `||` and recovered).
+ AteOr,
+ /// We did not eat anything (i.e. the current token is not `|` or `||`).
+ None,
+}
+
+impl<'a> Parser<'a> {
+ /// Parses a pattern.
+ ///
+ /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
+ /// at the top level. Used when parsing the parameters of lambda expressions,
+ /// functions, function pointers, and `pat` macro fragments.
+ pub fn parse_pat_no_top_alt(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
+ self.parse_pat_with_range_pat(true, expected)
+ }
+
+ /// Parses a pattern.
+ ///
+ /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
+ /// Used for parsing patterns in all cases when `pat<no_top_alt>` is not used.
+ ///
+ /// Note that after the FCP in <https://github.com/rust-lang/rust/issues/81415>,
+ /// a leading vert is allowed in nested or-patterns, too. This allows us to
+ /// simplify the grammar somewhat.
+ pub fn parse_pat_allow_top_alt(
+ &mut self,
+ expected: Expected,
+ rc: RecoverComma,
+ ra: RecoverColon,
+ rt: CommaRecoveryMode,
+ ) -> PResult<'a, P<Pat>> {
+ self.parse_pat_allow_top_alt_inner(expected, rc, ra, rt).map(|(pat, _)| pat)
+ }
+
+ /// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true =
+ /// recovered).
+ fn parse_pat_allow_top_alt_inner(
+ &mut self,
+ expected: Expected,
+ rc: RecoverComma,
+ ra: RecoverColon,
+ rt: CommaRecoveryMode,
+ ) -> PResult<'a, (P<Pat>, bool)> {
+ // Keep track of whether we recovered from a trailing vert so that we can avoid duplicated
+ // suggestions (which bothers rustfix).
+ //
+ // Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
+ let (leading_vert_span, mut trailing_vert) = match self.eat_or_separator(None) {
+ EatOrResult::AteOr => (Some(self.prev_token.span), false),
+ EatOrResult::TrailingVert => (None, true),
+ EatOrResult::None => (None, false),
+ };
+
+ // Parse the first pattern (`p_0`).
+ let mut first_pat = self.parse_pat_no_top_alt(expected)?;
+ if rc == RecoverComma::Yes {
+ self.maybe_recover_unexpected_comma(first_pat.span, rt)?;
+ }
+
+ // If the next token is not a `|`,
+ // this is not an or-pattern and we should exit here.
+ if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr {
+ // If we parsed a leading `|` which should be gated,
+ // then we should really gate the leading `|`.
+ // This complicated procedure is done purely for diagnostics UX.
+
+ // Check if the user wrote `foo:bar` instead of `foo::bar`.
+ if ra == RecoverColon::Yes {
+ first_pat = self.maybe_recover_colon_colon_in_pat_typo(first_pat, expected);
+ }
+
+ if let Some(leading_vert_span) = leading_vert_span {
+ // If there was a leading vert, treat this as an or-pattern. This improves
+ // diagnostics.
+ let span = leading_vert_span.to(self.prev_token.span);
+ return Ok((self.mk_pat(span, PatKind::Or(vec![first_pat])), trailing_vert));
+ }
+
+ return Ok((first_pat, trailing_vert));
+ }
+
+ // Parse the patterns `p_1 | ... | p_n` where `n > 0`.
+ let lo = leading_vert_span.unwrap_or(first_pat.span);
+ let mut pats = vec![first_pat];
+ loop {
+ match self.eat_or_separator(Some(lo)) {
+ EatOrResult::AteOr => {}
+ EatOrResult::None => break,
+ EatOrResult::TrailingVert => {
+ trailing_vert = true;
+ break;
+ }
+ }
+ let pat = self.parse_pat_no_top_alt(expected).map_err(|mut err| {
+ err.span_label(lo, WHILE_PARSING_OR_MSG);
+ err
+ })?;
+ if rc == RecoverComma::Yes {
+ self.maybe_recover_unexpected_comma(pat.span, rt)?;
+ }
+ pats.push(pat);
+ }
+ let or_pattern_span = lo.to(self.prev_token.span);
+
+ Ok((self.mk_pat(or_pattern_span, PatKind::Or(pats)), trailing_vert))
+ }
+
+ /// Parse a pattern and (maybe) a `Colon` in positions where a pattern may be followed by a
+ /// type annotation (e.g. for `let` bindings or `fn` params).
+ ///
+ /// Generally, this corresponds to `pat_no_top_alt` followed by an optional `Colon`. It will
+ /// eat the `Colon` token if one is present.
+ ///
+ /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
+ /// otherwise).
+ pub(super) fn parse_pat_before_ty(
+ &mut self,
+ expected: Expected,
+ rc: RecoverComma,
+ syntax_loc: &str,
+ ) -> PResult<'a, (P<Pat>, bool)> {
+ // We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level
+ // or-patterns so that we can detect when a user tries to use it. This allows us to print a
+ // better error message.
+ let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner(
+ expected,
+ rc,
+ RecoverColon::No,
+ CommaRecoveryMode::LikelyTuple,
+ )?;
+ let colon = self.eat(&token::Colon);
+
+ if let PatKind::Or(pats) = &pat.kind {
+ let msg = format!("top-level or-patterns are not allowed in {}", syntax_loc);
+ let (help, fix) = if pats.len() == 1 {
+ // If all we have is a leading vert, then print a special message. This is the case
+ // if `parse_pat_allow_top_alt` returns an or-pattern with one variant.
+ let msg = "remove the `|`";
+ let fix = pprust::pat_to_string(&pat);
+ (msg, fix)
+ } else {
+ let msg = "wrap the pattern in parentheses";
+ let fix = format!("({})", pprust::pat_to_string(&pat));
+ (msg, fix)
+ };
+
+ if trailing_vert {
+ // We already emitted an error and suggestion to remove the trailing vert. Don't
+ // emit again.
+ self.sess.span_diagnostic.delay_span_bug(pat.span, &msg);
+ } else {
+ self.struct_span_err(pat.span, &msg)
+ .span_suggestion(pat.span, help, fix, Applicability::MachineApplicable)
+ .emit();
+ }
+ }
+
+ Ok((pat, colon))
+ }
+
+ /// Parse the pattern for a function or function pointer parameter, followed by a colon.
+ ///
+ /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
+ /// otherwise).
+ pub(super) fn parse_fn_param_pat_colon(&mut self) -> PResult<'a, (P<Pat>, bool)> {
+ // In order to get good UX, we first recover in the case of a leading vert for an illegal
+ // top-level or-pat. Normally, this means recovering both `|` and `||`, but in this case,
+ // a leading `||` probably doesn't indicate an or-pattern attempt, so we handle that
+ // separately.
+ if let token::OrOr = self.token.kind {
+ let span = self.token.span;
+ let mut err = self.struct_span_err(span, "unexpected `||` before function parameter");
+ err.span_suggestion(span, "remove the `||`", "", Applicability::MachineApplicable);
+ err.note("alternatives in or-patterns are separated with `|`, not `||`");
+ err.emit();
+ self.bump();
+ }
+
+ self.parse_pat_before_ty(PARAM_EXPECTED, RecoverComma::No, "function parameters")
+ }
+
+ /// Eat the or-pattern `|` separator.
+ /// If instead a `||` token is encountered, recover and pretend we parsed `|`.
+ fn eat_or_separator(&mut self, lo: Option<Span>) -> EatOrResult {
+ if self.recover_trailing_vert(lo) {
+ EatOrResult::TrailingVert
+ } else if matches!(self.token.kind, token::OrOr) {
+ // Found `||`; Recover and pretend we parsed `|`.
+ self.ban_unexpected_or_or(lo);
+ self.bump();
+ EatOrResult::AteOr
+ } else if self.eat(&token::BinOp(token::Or)) {
+ EatOrResult::AteOr
+ } else {
+ EatOrResult::None
+ }
+ }
+
+ /// Recover if `|` or `||` is the current token and we have one of the
+ /// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us.
+ ///
+ /// These tokens all indicate that we reached the end of the or-pattern
+ /// list and can now reliably say that the `|` was an illegal trailing vert.
+ /// Note that there are more tokens such as `@` for which we know that the `|`
+ /// is an illegal parse. However, the user's intent is less clear in that case.
+ fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool {
+ let is_end_ahead = self.look_ahead(1, |token| {
+ matches!(
+ &token.uninterpolate().kind,
+ token::FatArrow // e.g. `a | => 0,`.
+ | token::Ident(kw::If, false) // e.g. `a | if expr`.
+ | token::Eq // e.g. `let a | = 0`.
+ | token::Semi // e.g. `let a |;`.
+ | token::Colon // e.g. `let a | :`.
+ | token::Comma // e.g. `let (a |,)`.
+ | token::CloseDelim(Delimiter::Bracket) // e.g. `let [a | ]`.
+ | token::CloseDelim(Delimiter::Parenthesis) // e.g. `let (a | )`.
+ | token::CloseDelim(Delimiter::Brace) // e.g. `let A { f: a | }`.
+ )
+ });
+ match (is_end_ahead, &self.token.kind) {
+ (true, token::BinOp(token::Or) | token::OrOr) => {
+ self.ban_illegal_vert(lo, "trailing", "not allowed in an or-pattern");
+ self.bump();
+ true
+ }
+ _ => false,
+ }
+ }
+
+ /// We have parsed `||` instead of `|`. Error and suggest `|` instead.
+ fn ban_unexpected_or_or(&mut self, lo: Option<Span>) {
+ let mut err = self.struct_span_err(self.token.span, "unexpected token `||` in pattern");
+ err.span_suggestion(
+ self.token.span,
+ "use a single `|` to separate multiple alternative patterns",
+ "|",
+ Applicability::MachineApplicable,
+ );
+ if let Some(lo) = lo {
+ err.span_label(lo, WHILE_PARSING_OR_MSG);
+ }
+ err.emit();
+ }
+
+ /// A `|` or possibly `||` token shouldn't be here. Ban it.
+ fn ban_illegal_vert(&mut self, lo: Option<Span>, pos: &str, ctx: &str) {
+ let span = self.token.span;
+ let mut err = self.struct_span_err(span, &format!("a {} `|` is {}", pos, ctx));
+ err.span_suggestion(
+ span,
+ &format!("remove the `{}`", pprust::token_to_string(&self.token)),
+ "",
+ Applicability::MachineApplicable,
+ );
+ if let Some(lo) = lo {
+ err.span_label(lo, WHILE_PARSING_OR_MSG);
+ }
+ if let token::OrOr = self.token.kind {
+ err.note("alternatives in or-patterns are separated with `|`, not `||`");
+ }
+ err.emit();
+ }
+
+ /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
+ /// allowed).
+ fn parse_pat_with_range_pat(
+ &mut self,
+ allow_range_pat: bool,
+ expected: Expected,
+ ) -> PResult<'a, P<Pat>> {
+ maybe_recover_from_interpolated_ty_qpath!(self, true);
+ maybe_whole!(self, NtPat, |x| x);
+
+ let lo = self.token.span;
+
+ let pat = if self.check(&token::BinOp(token::And)) || self.token.kind == token::AndAnd {
+ self.parse_pat_deref(expected)?
+ } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ self.parse_pat_tuple_or_parens()?
+ } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
+ // Parse `[pat, pat,...]` as a slice pattern.
+ let (pats, _) = self.parse_delim_comma_seq(Delimiter::Bracket, |p| {
+ p.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::No,
+ RecoverColon::No,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ )
+ })?;
+ PatKind::Slice(pats)
+ } else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
+ // A rest pattern `..`.
+ self.bump(); // `..`
+ PatKind::Rest
+ } else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) {
+ self.recover_dotdotdot_rest_pat(lo)
+ } else if let Some(form) = self.parse_range_end() {
+ self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
+ } else if self.eat_keyword(kw::Underscore) {
+ // Parse _
+ PatKind::Wild
+ } else if self.eat_keyword(kw::Mut) {
+ self.parse_pat_ident_mut()?
+ } else if self.eat_keyword(kw::Ref) {
+ // Parse ref ident @ pat / ref mut ident @ pat
+ let mutbl = self.parse_mutability();
+ self.parse_pat_ident(BindingMode::ByRef(mutbl))?
+ } else if self.eat_keyword(kw::Box) {
+ self.parse_pat_box()?
+ } else if self.check_inline_const(0) {
+ // Parse `const pat`
+ let const_expr = self.parse_const_block(lo.to(self.token.span), true)?;
+
+ if let Some(re) = self.parse_range_end() {
+ self.parse_pat_range_begin_with(const_expr, re)?
+ } else {
+ PatKind::Lit(const_expr)
+ }
+ } else if self.can_be_ident_pat() {
+ // Parse `ident @ pat`
+ // This can give false positives and parse nullary enums,
+ // they are dealt with later in resolve.
+ self.parse_pat_ident(BindingMode::ByValue(Mutability::Not))?
+ } else if self.is_start_of_pat_with_path() {
+ // Parse pattern starting with a path
+ let (qself, path) = if self.eat_lt() {
+ // Parse a qualified path
+ let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+ (Some(qself), path)
+ } else {
+ // Parse an unqualified path
+ (None, self.parse_path(PathStyle::Expr)?)
+ };
+ let span = lo.to(self.prev_token.span);
+
+ if qself.is_none() && self.check(&token::Not) {
+ self.parse_pat_mac_invoc(path)?
+ } else if let Some(form) = self.parse_range_end() {
+ let begin = self.mk_expr(span, ExprKind::Path(qself, path), AttrVec::new());
+ self.parse_pat_range_begin_with(begin, form)?
+ } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
+ self.parse_pat_struct(qself, path)?
+ } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ self.parse_pat_tuple_struct(qself, path)?
+ } else {
+ PatKind::Path(qself, path)
+ }
+ } else {
+ // Try to parse everything else as literal with optional minus
+ match self.parse_literal_maybe_minus() {
+ Ok(begin) => match self.parse_range_end() {
+ Some(form) => self.parse_pat_range_begin_with(begin, form)?,
+ None => PatKind::Lit(begin),
+ },
+ Err(err) => return self.fatal_unexpected_non_pat(err, expected),
+ }
+ };
+
+ let pat = self.mk_pat(lo.to(self.prev_token.span), pat);
+ let pat = self.maybe_recover_from_bad_qpath(pat)?;
+ let pat = self.recover_intersection_pat(pat)?;
+
+ if !allow_range_pat {
+ self.ban_pat_range_if_ambiguous(&pat)
+ }
+
+ Ok(pat)
+ }
+
+ /// Recover from a typoed `...` pattern that was encountered
+ /// Ref: Issue #70388
+ fn recover_dotdotdot_rest_pat(&mut self, lo: Span) -> PatKind {
+ // A typoed rest pattern `...`.
+ self.bump(); // `...`
+
+ // The user probably mistook `...` for a rest pattern `..`.
+ self.struct_span_err(lo, "unexpected `...`")
+ .span_label(lo, "not a valid pattern")
+ .span_suggestion_short(
+ lo,
+ "for a rest pattern, use `..` instead of `...`",
+ "..",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ PatKind::Rest
+ }
+
+ /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
+ ///
+ /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
+ /// should already have been parsed by now at this point,
+ /// if the next token is `@` then we can try to parse the more general form.
+ ///
+ /// Consult `parse_pat_ident` for the `binding` grammar.
+ ///
+ /// The notion of intersection patterns are found in
+ /// e.g. [F#][and] where they are called AND-patterns.
+ ///
+ /// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching
+ fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> {
+ if self.token.kind != token::At {
+ // Next token is not `@` so it's not going to be an intersection pattern.
+ return Ok(lhs);
+ }
+
+ // At this point we attempt to parse `@ $pat_rhs` and emit an error.
+ self.bump(); // `@`
+ let mut rhs = self.parse_pat_no_top_alt(None)?;
+ let sp = lhs.span.to(rhs.span);
+
+ if let PatKind::Ident(_, _, ref mut sub @ None) = rhs.kind {
+ // The user inverted the order, so help them fix that.
+ let mut applicability = Applicability::MachineApplicable;
+ // FIXME(bindings_after_at): Remove this code when stabilizing the feature.
+ lhs.walk(&mut |p| match p.kind {
+ // `check_match` is unhappy if the subpattern has a binding anywhere.
+ PatKind::Ident(..) => {
+ applicability = Applicability::MaybeIncorrect;
+ false // Short-circuit.
+ }
+ _ => true,
+ });
+
+ let lhs_span = lhs.span;
+ // Move the LHS into the RHS as a subpattern.
+ // The RHS is now the full pattern.
+ *sub = Some(lhs);
+
+ self.struct_span_err(sp, "pattern on wrong side of `@`")
+ .span_label(lhs_span, "pattern on the left, should be on the right")
+ .span_label(rhs.span, "binding on the right, should be on the left")
+ .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability)
+ .emit();
+ } else {
+ // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
+ rhs.kind = PatKind::Wild;
+ self.struct_span_err(sp, "left-hand side of `@` must be a binding")
+ .span_label(lhs.span, "interpreted as a pattern, not a binding")
+ .span_label(rhs.span, "also a pattern")
+ .note("bindings are `x`, `mut x`, `ref x`, and `ref mut x`")
+ .emit();
+ }
+
+ rhs.span = sp;
+ Ok(rhs)
+ }
+
+ /// Ban a range pattern if it has an ambiguous interpretation.
+ fn ban_pat_range_if_ambiguous(&self, pat: &Pat) {
+ match pat.kind {
+ PatKind::Range(
+ ..,
+ Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. },
+ ) => return,
+ PatKind::Range(..) => {}
+ _ => return,
+ }
+
+ self.struct_span_err(pat.span, "the range pattern here has ambiguous interpretation")
+ .span_suggestion(
+ pat.span,
+ "add parentheses to clarify the precedence",
+ format!("({})", pprust::pat_to_string(&pat)),
+ // "ambiguous interpretation" implies that we have to be guessing
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ /// Parse `&pat` / `&mut pat`.
+ fn parse_pat_deref(&mut self, expected: Expected) -> PResult<'a, PatKind> {
+ self.expect_and()?;
+ self.recover_lifetime_in_deref_pat();
+ let mutbl = self.parse_mutability();
+ let subpat = self.parse_pat_with_range_pat(false, expected)?;
+ Ok(PatKind::Ref(subpat, mutbl))
+ }
+
+ fn recover_lifetime_in_deref_pat(&mut self) {
+ if let token::Lifetime(name) = self.token.kind {
+ self.bump(); // `'a`
+
+ let span = self.prev_token.span;
+ self.struct_span_err(span, &format!("unexpected lifetime `{}` in pattern", name))
+ .span_suggestion(span, "remove the lifetime", "", Applicability::MachineApplicable)
+ .emit();
+ }
+ }
+
+ /// Parse a tuple or parenthesis pattern.
+ fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
+ let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
+ p.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::No,
+ RecoverColon::No,
+ CommaRecoveryMode::LikelyTuple,
+ )
+ })?;
+
+ // Here, `(pat,)` is a tuple pattern.
+ // For backward compatibility, `(..)` is a tuple pattern as well.
+ Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
+ PatKind::Paren(fields.into_iter().next().unwrap())
+ } else {
+ PatKind::Tuple(fields)
+ })
+ }
+
+ /// Parse a mutable binding with the `mut` token already eaten.
+ fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
+ let mut_span = self.prev_token.span;
+
+ if self.eat_keyword(kw::Ref) {
+ return self.recover_mut_ref_ident(mut_span);
+ }
+
+ self.recover_additional_muts();
+
+ // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
+ if let token::Interpolated(ref nt) = self.token.kind {
+ if let token::NtPat(_) = **nt {
+ self.expected_ident_found().emit();
+ }
+ }
+
+ // Parse the pattern we hope to be an identifier.
+ let mut pat = self.parse_pat_no_top_alt(Some("identifier"))?;
+
+ // If we don't have `mut $ident (@ pat)?`, error.
+ if let PatKind::Ident(BindingMode::ByValue(m @ Mutability::Not), ..) = &mut pat.kind {
+ // Don't recurse into the subpattern.
+ // `mut` on the outer binding doesn't affect the inner bindings.
+ *m = Mutability::Mut;
+ } else {
+ // Add `mut` to any binding in the parsed pattern.
+ let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
+ self.ban_mut_general_pat(mut_span, &pat, changed_any_binding);
+ }
+
+ Ok(pat.into_inner().kind)
+ }
+
+ /// Recover on `mut ref? ident @ pat` and suggest
+ /// that the order of `mut` and `ref` is incorrect.
+ fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> {
+ let mutref_span = lo.to(self.prev_token.span);
+ self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
+ .span_suggestion(
+ mutref_span,
+ "try switching the order",
+ "ref mut",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ self.parse_pat_ident(BindingMode::ByRef(Mutability::Mut))
+ }
+
+ /// Turn all by-value immutable bindings in a pattern into mutable bindings.
+ /// Returns `true` if any change was made.
+ fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
+ struct AddMut(bool);
+ impl MutVisitor for AddMut {
+ fn visit_pat(&mut self, pat: &mut P<Pat>) {
+ if let PatKind::Ident(BindingMode::ByValue(m @ Mutability::Not), ..) = &mut pat.kind
+ {
+ self.0 = true;
+ *m = Mutability::Mut;
+ }
+ noop_visit_pat(pat, self);
+ }
+ }
+
+ let mut add_mut = AddMut(false);
+ add_mut.visit_pat(pat);
+ add_mut.0
+ }
+
+ /// Error on `mut $pat` where `$pat` is not an ident.
+ fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
+ let span = lo.to(pat.span);
+ let fix = pprust::pat_to_string(&pat);
+ let (problem, suggestion) = if changed_any_binding {
+ ("`mut` must be attached to each individual binding", "add `mut` to each binding")
+ } else {
+ ("`mut` must be followed by a named binding", "remove the `mut` prefix")
+ };
+ self.struct_span_err(span, problem)
+ .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable)
+ .note("`mut` may be followed by `variable` and `variable @ pattern`")
+ .emit();
+ }
+
+ /// Eat any extraneous `mut`s and error + recover if we ate any.
+ fn recover_additional_muts(&mut self) {
+ let lo = self.token.span;
+ while self.eat_keyword(kw::Mut) {}
+ if lo == self.token.span {
+ return;
+ }
+
+ let span = lo.to(self.prev_token.span);
+ self.struct_span_err(span, "`mut` on a binding may not be repeated")
+ .span_suggestion(
+ span,
+ "remove the additional `mut`s",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ /// Parse macro invocation
+ fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
+ self.bump();
+ let args = self.parse_mac_args()?;
+ let mac = MacCall { path, args, prior_type_ascription: self.last_type_ascription };
+ Ok(PatKind::MacCall(mac))
+ }
+
+ fn fatal_unexpected_non_pat(
+ &mut self,
+ err: DiagnosticBuilder<'a, ErrorGuaranteed>,
+ expected: Expected,
+ ) -> PResult<'a, P<Pat>> {
+ err.cancel();
+
+ let expected = expected.unwrap_or("pattern");
+ let msg = format!("expected {}, found {}", expected, super::token_descr(&self.token));
+
+ let mut err = self.struct_span_err(self.token.span, &msg);
+ err.span_label(self.token.span, format!("expected {}", expected));
+
+ let sp = self.sess.source_map().start_point(self.token.span);
+ if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
+ self.sess.expr_parentheses_needed(&mut err, *sp);
+ }
+
+ Err(err)
+ }
+
+ /// Parses the range pattern end form `".." | "..." | "..=" ;`.
+ fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> {
+ let re = if self.eat(&token::DotDotDot) {
+ RangeEnd::Included(RangeSyntax::DotDotDot)
+ } else if self.eat(&token::DotDotEq) {
+ RangeEnd::Included(RangeSyntax::DotDotEq)
+ } else if self.eat(&token::DotDot) {
+ RangeEnd::Excluded
+ } else {
+ return None;
+ };
+ Some(respan(self.prev_token.span, re))
+ }
+
+ /// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`.
+ /// `$begin $form` has already been parsed.
+ fn parse_pat_range_begin_with(
+ &mut self,
+ begin: P<Expr>,
+ re: Spanned<RangeEnd>,
+ ) -> PResult<'a, PatKind> {
+ let end = if self.is_pat_range_end_start(0) {
+ // Parsing e.g. `X..=Y`.
+ Some(self.parse_pat_range_end()?)
+ } else {
+ // Parsing e.g. `X..`.
+ if let RangeEnd::Included(_) = re.node {
+ // FIXME(Centril): Consider semantic errors instead in `ast_validation`.
+ self.inclusive_range_with_incorrect_end(re.span);
+ }
+ None
+ };
+ Ok(PatKind::Range(Some(begin), end, re))
+ }
+
+ pub(super) fn inclusive_range_with_incorrect_end(&mut self, span: Span) {
+ let tok = &self.token;
+
+ // If the user typed "..==" instead of "..=", we want to give them
+ // a specific error message telling them to use "..=".
+ // Otherwise, we assume that they meant to type a half open exclusive
+ // range and give them an error telling them to do that instead.
+ if matches!(tok.kind, token::Eq) && tok.span.lo() == span.hi() {
+ let span_with_eq = span.to(tok.span);
+
+ // Ensure the user doesn't receive unhelpful unexpected token errors
+ self.bump();
+ if self.is_pat_range_end_start(0) {
+ let _ = self.parse_pat_range_end().map_err(|e| e.cancel());
+ }
+
+ self.error_inclusive_range_with_extra_equals(span_with_eq);
+ } else {
+ self.error_inclusive_range_with_no_end(span);
+ }
+ }
+
+ fn error_inclusive_range_with_extra_equals(&self, span: Span) {
+ self.struct_span_err(span, "unexpected `=` after inclusive range")
+ .span_suggestion_short(span, "use `..=` instead", "..=", Applicability::MaybeIncorrect)
+ .note("inclusive ranges end with a single equals sign (`..=`)")
+ .emit();
+ }
+
+ fn error_inclusive_range_with_no_end(&self, span: Span) {
+ struct_span_err!(self.sess.span_diagnostic, span, E0586, "inclusive range with no end")
+ .span_suggestion_short(span, "use `..` instead", "..", Applicability::MachineApplicable)
+ .note("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)")
+ .emit();
+ }
+
+ /// Parse a range-to pattern, `..X` or `..=X` where `X` remains to be parsed.
+ ///
+ /// The form `...X` is prohibited to reduce confusion with the potential
+ /// expression syntax `...expr` for splatting in expressions.
+ fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> {
+ let end = self.parse_pat_range_end()?;
+ self.sess.gated_spans.gate(sym::half_open_range_patterns, re.span.to(self.prev_token.span));
+ if let RangeEnd::Included(ref mut syn @ RangeSyntax::DotDotDot) = &mut re.node {
+ *syn = RangeSyntax::DotDotEq;
+ self.struct_span_err(re.span, "range-to patterns with `...` are not allowed")
+ .span_suggestion_short(
+ re.span,
+ "use `..=` instead",
+ "..=",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+ Ok(PatKind::Range(None, Some(end), re))
+ }
+
+ /// Is the token `dist` away from the current suitable as the start of a range patterns end?
+ fn is_pat_range_end_start(&self, dist: usize) -> bool {
+ self.check_inline_const(dist)
+ || self.look_ahead(dist, |t| {
+ t.is_path_start() // e.g. `MY_CONST`;
+ || t.kind == token::Dot // e.g. `.5` for recovery;
+ || t.can_begin_literal_maybe_minus() // e.g. `42`.
+ || t.is_whole_expr()
+ })
+ }
+
+ fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
+ if self.check_inline_const(0) {
+ self.parse_const_block(self.token.span, true)
+ } else if self.check_path() {
+ let lo = self.token.span;
+ let (qself, path) = if self.eat_lt() {
+ // Parse a qualified path
+ let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+ (Some(qself), path)
+ } else {
+ // Parse an unqualified path
+ (None, self.parse_path(PathStyle::Expr)?)
+ };
+ let hi = self.prev_token.span;
+ Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), AttrVec::new()))
+ } else {
+ self.parse_literal_maybe_minus()
+ }
+ }
+
+ /// Is this the start of a pattern beginning with a path?
+ fn is_start_of_pat_with_path(&mut self) -> bool {
+ self.check_path()
+ // Just for recovery (see `can_be_ident`).
+ || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
+ }
+
+ /// Would `parse_pat_ident` be appropriate here?
+ fn can_be_ident_pat(&mut self) -> bool {
+ self.check_ident()
+ && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
+ && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
+ // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
+ && !self.token.is_keyword(kw::In)
+ // Try to do something more complex?
+ && self.look_ahead(1, |t| !matches!(t.kind, token::OpenDelim(Delimiter::Parenthesis) // A tuple struct pattern.
+ | token::OpenDelim(Delimiter::Brace) // A struct pattern.
+ | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
+ | token::ModSep // A tuple / struct variant pattern.
+ | token::Not)) // A macro expanding to a pattern.
+ }
+
+ /// Parses `ident` or `ident @ pat`.
+ /// Used by the copy foo and ref foo patterns to give a good
+ /// error message when parsing mistakes like `ref foo(a, b)`.
+ fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
+ let ident = self.parse_ident()?;
+ let sub = if self.eat(&token::At) {
+ Some(self.parse_pat_no_top_alt(Some("binding pattern"))?)
+ } else {
+ None
+ };
+
+ // Just to be friendly, if they write something like `ref Some(i)`,
+ // we end up here with `(` as the current token.
+ // This shortly leads to a parse error. Note that if there is no explicit
+ // binding mode then we do not end up here, because the lookahead
+ // will direct us over to `parse_enum_variant()`.
+ if self.token == token::OpenDelim(Delimiter::Parenthesis) {
+ return Err(self
+ .struct_span_err(self.prev_token.span, "expected identifier, found enum pattern"));
+ }
+
+ Ok(PatKind::Ident(binding_mode, ident, sub))
+ }
+
+ /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
+ fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
+ if qself.is_some() {
+ // Feature gate the use of qualified paths in patterns
+ self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
+ }
+ self.bump();
+ let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
+ e.span_label(path.span, "while parsing the fields for this pattern");
+ e.emit();
+ self.recover_stmt();
+ (vec![], true)
+ });
+ self.bump();
+ Ok(PatKind::Struct(qself, path, fields, etc))
+ }
+
+ /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
+ fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
+ let (fields, _) = self.parse_paren_comma_seq(|p| {
+ p.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::No,
+ RecoverColon::No,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ )
+ })?;
+ if qself.is_some() {
+ self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
+ }
+ Ok(PatKind::TupleStruct(qself, path, fields))
+ }
+
+ /// Are we sure this could not possibly be the start of a pattern?
+ ///
+ /// Currently, this only accounts for tokens that can follow identifiers
+ /// in patterns, but this can be extended as necessary.
+ fn isnt_pattern_start(&self) -> bool {
+ [
+ token::Eq,
+ token::Colon,
+ token::Comma,
+ token::Semi,
+ token::At,
+ token::OpenDelim(Delimiter::Brace),
+ token::CloseDelim(Delimiter::Brace),
+ token::CloseDelim(Delimiter::Parenthesis),
+ ]
+ .contains(&self.token.kind)
+ }
+
+ /// Parses `box pat`
+ fn parse_pat_box(&mut self) -> PResult<'a, PatKind> {
+ let box_span = self.prev_token.span;
+
+ if self.isnt_pattern_start() {
+ self.struct_span_err(
+ self.token.span,
+ format!("expected pattern, found {}", super::token_descr(&self.token)),
+ )
+ .span_note(box_span, "`box` is a reserved keyword")
+ .span_suggestion_verbose(
+ box_span.shrink_to_lo(),
+ "escape `box` to use it as an identifier",
+ "r#",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+
+ // We cannot use `parse_pat_ident()` since it will complain `box`
+ // is not an identifier.
+ let sub = if self.eat(&token::At) {
+ Some(self.parse_pat_no_top_alt(Some("binding pattern"))?)
+ } else {
+ None
+ };
+
+ Ok(PatKind::Ident(
+ BindingMode::ByValue(Mutability::Not),
+ Ident::new(kw::Box, box_span),
+ sub,
+ ))
+ } else {
+ let pat = self.parse_pat_with_range_pat(false, None)?;
+ self.sess.gated_spans.gate(sym::box_patterns, box_span.to(self.prev_token.span));
+ Ok(PatKind::Box(pat))
+ }
+ }
+
+ /// Parses the fields of a struct-like pattern.
+ fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<PatField>, bool)> {
+ let mut fields = Vec::new();
+ let mut etc = false;
+ let mut ate_comma = true;
+ let mut delayed_err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>> = None;
+ let mut etc_span = None;
+
+ while self.token != token::CloseDelim(Delimiter::Brace) {
+ let attrs = match self.parse_outer_attributes() {
+ Ok(attrs) => attrs,
+ Err(err) => {
+ if let Some(mut delayed) = delayed_err {
+ delayed.emit();
+ }
+ return Err(err);
+ }
+ };
+ let lo = self.token.span;
+
+ // check that a comma comes after every field
+ if !ate_comma {
+ let err = self.struct_span_err(self.token.span, "expected `,`");
+ if let Some(mut delayed) = delayed_err {
+ delayed.emit();
+ }
+ return Err(err);
+ }
+ ate_comma = false;
+
+ if self.check(&token::DotDot) || self.token == token::DotDotDot {
+ etc = true;
+ let mut etc_sp = self.token.span;
+
+ self.recover_one_fewer_dotdot();
+ self.bump(); // `..` || `...`
+
+ if self.token == token::CloseDelim(Delimiter::Brace) {
+ etc_span = Some(etc_sp);
+ break;
+ }
+ let token_str = super::token_descr(&self.token);
+ let msg = &format!("expected `}}`, found {}", token_str);
+ let mut err = self.struct_span_err(self.token.span, msg);
+
+ err.span_label(self.token.span, "expected `}`");
+ let mut comma_sp = None;
+ if self.token == token::Comma {
+ // Issue #49257
+ let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
+ etc_sp = etc_sp.to(nw_span);
+ err.span_label(
+ etc_sp,
+ "`..` must be at the end and cannot have a trailing comma",
+ );
+ comma_sp = Some(self.token.span);
+ self.bump();
+ ate_comma = true;
+ }
+
+ etc_span = Some(etc_sp.until(self.token.span));
+ if self.token == token::CloseDelim(Delimiter::Brace) {
+ // If the struct looks otherwise well formed, recover and continue.
+ if let Some(sp) = comma_sp {
+ err.span_suggestion_short(
+ sp,
+ "remove this comma",
+ "",
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ break;
+ } else if self.token.is_ident() && ate_comma {
+ // Accept fields coming after `..,`.
+ // This way we avoid "pattern missing fields" errors afterwards.
+ // We delay this error until the end in order to have a span for a
+ // suggested fix.
+ if let Some(mut delayed_err) = delayed_err {
+ delayed_err.emit();
+ return Err(err);
+ } else {
+ delayed_err = Some(err);
+ }
+ } else {
+ if let Some(mut err) = delayed_err {
+ err.emit();
+ }
+ return Err(err);
+ }
+ }
+
+ let field =
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let field = match this.parse_pat_field(lo, attrs) {
+ Ok(field) => Ok(field),
+ Err(err) => {
+ if let Some(mut delayed_err) = delayed_err.take() {
+ delayed_err.emit();
+ }
+ return Err(err);
+ }
+ }?;
+ ate_comma = this.eat(&token::Comma);
+ // We just ate a comma, so there's no need to use
+ // `TrailingToken::Comma`
+ Ok((field, TrailingToken::None))
+ })?;
+
+ fields.push(field)
+ }
+
+ if let Some(mut err) = delayed_err {
+ if let Some(etc_span) = etc_span {
+ err.multipart_suggestion(
+ "move the `..` to the end of the field list",
+ vec![
+ (etc_span, String::new()),
+ (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
+ ],
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ }
+ Ok((fields, etc))
+ }
+
+ /// Recover on `...` as if it were `..` to avoid further errors.
+ /// See issue #46718.
+ fn recover_one_fewer_dotdot(&self) {
+ if self.token != token::DotDotDot {
+ return;
+ }
+
+ self.struct_span_err(self.token.span, "expected field pattern, found `...`")
+ .span_suggestion(
+ self.token.span,
+ "to omit remaining fields, use one fewer `.`",
+ "..",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ fn parse_pat_field(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, PatField> {
+ // Check if a colon exists one ahead. This means we're parsing a fieldname.
+ let hi;
+ let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
+ // Parsing a pattern of the form `fieldname: pat`.
+ let fieldname = self.parse_field_name()?;
+ self.bump();
+ let pat = self.parse_pat_allow_top_alt(
+ None,
+ RecoverComma::No,
+ RecoverColon::No,
+ CommaRecoveryMode::EitherTupleOrPipe,
+ )?;
+ hi = pat.span;
+ (pat, fieldname, false)
+ } else {
+ // Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
+ let is_box = self.eat_keyword(kw::Box);
+ let boxed_span = self.token.span;
+ let is_ref = self.eat_keyword(kw::Ref);
+ let is_mut = self.eat_keyword(kw::Mut);
+ let fieldname = self.parse_field_name()?;
+ hi = self.prev_token.span;
+
+ let bind_type = match (is_ref, is_mut) {
+ (true, true) => BindingMode::ByRef(Mutability::Mut),
+ (true, false) => BindingMode::ByRef(Mutability::Not),
+ (false, true) => BindingMode::ByValue(Mutability::Mut),
+ (false, false) => BindingMode::ByValue(Mutability::Not),
+ };
+
+ let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
+ let subpat =
+ if is_box { self.mk_pat(lo.to(hi), PatKind::Box(fieldpat)) } else { fieldpat };
+ (subpat, fieldname, true)
+ };
+
+ Ok(PatField {
+ ident: fieldname,
+ pat: subpat,
+ is_shorthand,
+ attrs: attrs.into(),
+ id: ast::DUMMY_NODE_ID,
+ span: lo.to(hi),
+ is_placeholder: false,
+ })
+ }
+
+ pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
+ self.mk_pat(span, PatKind::Ident(bm, ident, None))
+ }
+
+ pub(super) fn mk_pat(&self, span: Span, kind: PatKind) -> P<Pat> {
+ P(Pat { kind, span, id: ast::DUMMY_NODE_ID, tokens: None })
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
new file mode 100644
index 000000000..5cf1758c3
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -0,0 +1,754 @@
+use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
+use super::{Parser, Restrictions, TokenType};
+use crate::maybe_whole;
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::{
+ self as ast, AngleBracketedArg, AngleBracketedArgs, AnonConst, AssocConstraint,
+ AssocConstraintKind, BlockCheckMode, GenericArg, GenericArgs, Generics, ParenthesizedArgs,
+ Path, PathSegment, QSelf,
+};
+use rustc_errors::{pluralize, Applicability, PResult};
+use rustc_span::source_map::{BytePos, Span};
+use rustc_span::symbol::{kw, sym, Ident};
+
+use std::mem;
+use tracing::debug;
+
+/// Specifies how to parse a path.
+#[derive(Copy, Clone, PartialEq)]
+pub enum PathStyle {
+ /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
+ /// with something else. For example, in expressions `segment < ....` can be interpreted
+ /// as a comparison and `segment ( ....` can be interpreted as a function call.
+ /// In all such contexts the non-path interpretation is preferred by default for practical
+ /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
+ /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
+ Expr,
+ /// In other contexts, notably in types, no ambiguity exists and paths can be written
+ /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
+ /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
+ Type,
+ /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
+ /// visibilities or attributes.
+ /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
+ /// (paths in "mod" contexts have to be checked later for absence of generic arguments
+ /// anyway, due to macros), but it is used to avoid weird suggestions about expected
+ /// tokens when something goes wrong.
+ Mod,
+}
+
+impl<'a> Parser<'a> {
+ /// Parses a qualified path.
+ /// Assumes that the leading `<` has been parsed already.
+ ///
+ /// `qualified_path = <type [as trait_ref]>::path`
+ ///
+ /// # Examples
+ /// `<T>::default`
+ /// `<T as U>::a`
+ /// `<T as U>::F::a<S>` (without disambiguator)
+ /// `<T as U>::F::a::<S>` (with disambiguator)
+ pub(super) fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, Path)> {
+ let lo = self.prev_token.span;
+ let ty = self.parse_ty()?;
+
+ // `path` will contain the prefix of the path up to the `>`,
+ // if any (e.g., `U` in the `<T as U>::*` examples
+ // above). `path_span` has the span of that path, or an empty
+ // span in the case of something like `<T>::Bar`.
+ let (mut path, path_span);
+ if self.eat_keyword(kw::As) {
+ let path_lo = self.token.span;
+ path = self.parse_path(PathStyle::Type)?;
+ path_span = path_lo.to(self.prev_token.span);
+ } else {
+ path_span = self.token.span.to(self.token.span);
+ path = ast::Path { segments: Vec::new(), span: path_span, tokens: None };
+ }
+
+ // See doc comment for `unmatched_angle_bracket_count`.
+ self.expect(&token::Gt)?;
+ if self.unmatched_angle_bracket_count > 0 {
+ self.unmatched_angle_bracket_count -= 1;
+ debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
+ }
+
+ if !self.recover_colon_before_qpath_proj() {
+ self.expect(&token::ModSep)?;
+ }
+
+ let qself = QSelf { ty, path_span, position: path.segments.len() };
+ self.parse_path_segments(&mut path.segments, style, None)?;
+
+ Ok((
+ qself,
+ Path { segments: path.segments, span: lo.to(self.prev_token.span), tokens: None },
+ ))
+ }
+
+ /// Recover from an invalid single colon, when the user likely meant a qualified path.
+ /// We avoid emitting this if not followed by an identifier, as our assumption that the user
+ /// intended this to be a qualified path may not be correct.
+ ///
+ /// ```ignore (diagnostics)
+ /// <Bar as Baz<T>>:Qux
+ /// ^ help: use double colon
+ /// ```
+ fn recover_colon_before_qpath_proj(&mut self) -> bool {
+ if !self.check_noexpect(&TokenKind::Colon)
+ || self.look_ahead(1, |t| !t.is_ident() || t.is_reserved_ident())
+ {
+ return false;
+ }
+
+ self.bump(); // colon
+
+ self.diagnostic()
+ .struct_span_err(
+ self.prev_token.span,
+ "found single colon before projection in qualified path",
+ )
+ .span_suggestion(
+ self.prev_token.span,
+ "use double colon",
+ "::",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ true
+ }
+
+ pub(super) fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
+ self.parse_path_inner(style, None)
+ }
+
+ /// Parses simple paths.
+ ///
+ /// `path = [::] segment+`
+ /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
+ ///
+ /// # Examples
+ /// `a::b::C<D>` (without disambiguator)
+ /// `a::b::C::<D>` (with disambiguator)
+ /// `Fn(Args)` (without disambiguator)
+ /// `Fn::(Args)` (with disambiguator)
+ pub(super) fn parse_path_inner(
+ &mut self,
+ style: PathStyle,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Path> {
+ let reject_generics_if_mod_style = |parser: &Parser<'_>, path: &Path| {
+ // Ensure generic arguments don't end up in attribute paths, such as:
+ //
+ // macro_rules! m {
+ // ($p:path) => { #[$p] struct S; }
+ // }
+ //
+ // m!(inline<u8>); //~ ERROR: unexpected generic arguments in path
+ //
+ if style == PathStyle::Mod && path.segments.iter().any(|segment| segment.args.is_some())
+ {
+ parser
+ .struct_span_err(
+ path.segments
+ .iter()
+ .filter_map(|segment| segment.args.as_ref())
+ .map(|arg| arg.span())
+ .collect::<Vec<_>>(),
+ "unexpected generic arguments in path",
+ )
+ .emit();
+ }
+ };
+
+ maybe_whole!(self, NtPath, |path| {
+ reject_generics_if_mod_style(self, &path);
+ path.into_inner()
+ });
+
+ if let token::Interpolated(nt) = &self.token.kind {
+ if let token::NtTy(ty) = &**nt {
+ if let ast::TyKind::Path(None, path) = &ty.kind {
+ let path = path.clone();
+ self.bump();
+ reject_generics_if_mod_style(self, &path);
+ return Ok(path);
+ }
+ }
+ }
+
+ let lo = self.token.span;
+ let mut segments = Vec::new();
+ let mod_sep_ctxt = self.token.span.ctxt();
+ if self.eat(&token::ModSep) {
+ segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
+ }
+ self.parse_path_segments(&mut segments, style, ty_generics)?;
+
+ Ok(Path { segments, span: lo.to(self.prev_token.span), tokens: None })
+ }
+
+ pub(super) fn parse_path_segments(
+ &mut self,
+ segments: &mut Vec<PathSegment>,
+ style: PathStyle,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, ()> {
+ loop {
+ let segment = self.parse_path_segment(style, ty_generics)?;
+ if style == PathStyle::Expr {
+ // In order to check for trailing angle brackets, we must have finished
+ // recursing (`parse_path_segment` can indirectly call this function),
+ // that is, the next token must be the highlighted part of the below example:
+ //
+ // `Foo::<Bar as Baz<T>>::Qux`
+ // ^ here
+ //
+ // As opposed to the below highlight (if we had only finished the first
+ // recursion):
+ //
+ // `Foo::<Bar as Baz<T>>::Qux`
+ // ^ here
+ //
+ // `PathStyle::Expr` is only provided at the root invocation and never in
+ // `parse_path_segment` to recurse and therefore can be checked to maintain
+ // this invariant.
+ self.check_trailing_angle_brackets(&segment, &[&token::ModSep]);
+ }
+ segments.push(segment);
+
+ if self.is_import_coupler() || !self.eat(&token::ModSep) {
+ return Ok(());
+ }
+ }
+ }
+
+ pub(super) fn parse_path_segment(
+ &mut self,
+ style: PathStyle,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, PathSegment> {
+ let ident = self.parse_path_segment_ident()?;
+ let is_args_start = |token: &Token| {
+ matches!(
+ token.kind,
+ token::Lt
+ | token::BinOp(token::Shl)
+ | token::OpenDelim(Delimiter::Parenthesis)
+ | token::LArrow
+ )
+ };
+ let check_args_start = |this: &mut Self| {
+ this.expected_tokens.extend_from_slice(&[
+ TokenType::Token(token::Lt),
+ TokenType::Token(token::OpenDelim(Delimiter::Parenthesis)),
+ ]);
+ is_args_start(&this.token)
+ };
+
+ Ok(
+ if style == PathStyle::Type && check_args_start(self)
+ || style != PathStyle::Mod
+ && self.check(&token::ModSep)
+ && self.look_ahead(1, |t| is_args_start(t))
+ {
+ // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
+ // it isn't, then we reset the unmatched angle bracket count as we're about to start
+ // parsing a new path.
+ if style == PathStyle::Expr {
+ self.unmatched_angle_bracket_count = 0;
+ self.max_angle_bracket_count = 0;
+ }
+
+ // Generic arguments are found - `<`, `(`, `::<` or `::(`.
+ self.eat(&token::ModSep);
+ let lo = self.token.span;
+ let args = if self.eat_lt() {
+ // `<'a, T, A = U>`
+ let args = self.parse_angle_args_with_leading_angle_bracket_recovery(
+ style,
+ lo,
+ ty_generics,
+ )?;
+ self.expect_gt().map_err(|mut err| {
+ // Attempt to find places where a missing `>` might belong.
+ if let Some(arg) = args
+ .iter()
+ .rev()
+ .skip_while(|arg| matches!(arg, AngleBracketedArg::Constraint(_)))
+ .next()
+ {
+ err.span_suggestion_verbose(
+ arg.span().shrink_to_hi(),
+ "you might have meant to end the type parameters here",
+ ">",
+ Applicability::MaybeIncorrect,
+ );
+ }
+ err
+ })?;
+ let span = lo.to(self.prev_token.span);
+ AngleBracketedArgs { args, span }.into()
+ } else {
+ // `(T, U) -> R`
+ let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
+ let inputs_span = lo.to(self.prev_token.span);
+ let output =
+ self.parse_ret_ty(AllowPlus::No, RecoverQPath::No, RecoverReturnSign::No)?;
+ let span = ident.span.to(self.prev_token.span);
+ ParenthesizedArgs { span, inputs, inputs_span, output }.into()
+ };
+
+ PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
+ } else {
+ // Generic arguments are not found.
+ PathSegment::from_ident(ident)
+ },
+ )
+ }
+
+ pub(super) fn parse_path_segment_ident(&mut self) -> PResult<'a, Ident> {
+ match self.token.ident() {
+ Some((ident, false)) if ident.is_path_segment_keyword() => {
+ self.bump();
+ Ok(ident)
+ }
+ _ => self.parse_ident(),
+ }
+ }
+
+ /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
+ /// For the purposes of understanding the parsing logic of generic arguments, this function
+ /// can be thought of being the same as just calling `self.parse_angle_args()` if the source
+ /// had the correct amount of leading angle brackets.
+ ///
+ /// ```ignore (diagnostics)
+ /// bar::<<<<T as Foo>::Output>();
+ /// ^^ help: remove extra angle brackets
+ /// ```
+ fn parse_angle_args_with_leading_angle_bracket_recovery(
+ &mut self,
+ style: PathStyle,
+ lo: Span,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Vec<AngleBracketedArg>> {
+ // We need to detect whether there are extra leading left angle brackets and produce an
+ // appropriate error and suggestion. This cannot be implemented by looking ahead at
+ // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
+ // then there won't be matching `>` tokens to find.
+ //
+ // To explain how this detection works, consider the following example:
+ //
+ // ```ignore (diagnostics)
+ // bar::<<<<T as Foo>::Output>();
+ // ^^ help: remove extra angle brackets
+ // ```
+ //
+ // Parsing of the left angle brackets starts in this function. We start by parsing the
+ // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
+ // `eat_lt`):
+ //
+ // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
+ // *Unmatched count:* 1
+ // *`parse_path_segment` calls deep:* 0
+ //
+ // This has the effect of recursing as this function is called if a `<` character
+ // is found within the expected generic arguments:
+ //
+ // *Upcoming tokens:* `<<<T as Foo>::Output>;`
+ // *Unmatched count:* 2
+ // *`parse_path_segment` calls deep:* 1
+ //
+ // Eventually we will have recursed until having consumed all of the `<` tokens and
+ // this will be reflected in the count:
+ //
+ // *Upcoming tokens:* `T as Foo>::Output>;`
+ // *Unmatched count:* 4
+ // `parse_path_segment` calls deep:* 3
+ //
+ // The parser will continue until reaching the first `>` - this will decrement the
+ // unmatched angle bracket count and return to the parent invocation of this function
+ // having succeeded in parsing:
+ //
+ // *Upcoming tokens:* `::Output>;`
+ // *Unmatched count:* 3
+ // *`parse_path_segment` calls deep:* 2
+ //
+ // This will continue until the next `>` character which will also return successfully
+ // to the parent invocation of this function and decrement the count:
+ //
+ // *Upcoming tokens:* `;`
+ // *Unmatched count:* 2
+ // *`parse_path_segment` calls deep:* 1
+ //
+ // At this point, this function will expect to find another matching `>` character but
+ // won't be able to and will return an error. This will continue all the way up the
+ // call stack until the first invocation:
+ //
+ // *Upcoming tokens:* `;`
+ // *Unmatched count:* 2
+ // *`parse_path_segment` calls deep:* 0
+ //
+ // In doing this, we have managed to work out how many unmatched leading left angle
+ // brackets there are, but we cannot recover as the unmatched angle brackets have
+ // already been consumed. To remedy this, we keep a snapshot of the parser state
+ // before we do the above. We can then inspect whether we ended up with a parsing error
+ // and unmatched left angle brackets and if so, restore the parser state before we
+ // consumed any `<` characters to emit an error and consume the erroneous tokens to
+ // recover by attempting to parse again.
+ //
+ // In practice, the recursion of this function is indirect and there will be other
+ // locations that consume some `<` characters - as long as we update the count when
+ // this happens, it isn't an issue.
+
+ let is_first_invocation = style == PathStyle::Expr;
+ // Take a snapshot before attempting to parse - we can restore this later.
+ let snapshot = if is_first_invocation { Some(self.clone()) } else { None };
+
+ debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
+ match self.parse_angle_args(ty_generics) {
+ Ok(args) => Ok(args),
+ Err(e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
+ // Swap `self` with our backup of the parser state before attempting to parse
+ // generic arguments.
+ let snapshot = mem::replace(self, snapshot.unwrap());
+
+ // Eat the unmatched angle brackets.
+ let all_angle_brackets = (0..snapshot.unmatched_angle_bracket_count)
+ .fold(true, |a, _| a && self.eat_lt());
+
+ if !all_angle_brackets {
+ // If there are other tokens in between the extraneous `<`s, we cannot simply
+ // suggest to remove them. This check also prevents us from accidentally ending
+ // up in the middle of a multibyte character (issue #84104).
+ let _ = mem::replace(self, snapshot);
+ Err(e)
+ } else {
+ // Cancel error from being unable to find `>`. We know the error
+ // must have been this due to a non-zero unmatched angle bracket
+ // count.
+ e.cancel();
+
+ debug!(
+ "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
+ snapshot.count={:?}",
+ snapshot.unmatched_angle_bracket_count,
+ );
+
+ // Make a span over ${unmatched angle bracket count} characters.
+ // This is safe because `all_angle_brackets` ensures that there are only `<`s,
+ // i.e. no multibyte characters, in this range.
+ let span =
+ lo.with_hi(lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count));
+ self.struct_span_err(
+ span,
+ &format!(
+ "unmatched angle bracket{}",
+ pluralize!(snapshot.unmatched_angle_bracket_count)
+ ),
+ )
+ .span_suggestion(
+ span,
+ &format!(
+ "remove extra angle bracket{}",
+ pluralize!(snapshot.unmatched_angle_bracket_count)
+ ),
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ // Try again without unmatched angle bracket characters.
+ self.parse_angle_args(ty_generics)
+ }
+ }
+ Err(e) => Err(e),
+ }
+ }
+
+ /// Parses (possibly empty) list of generic arguments / associated item constraints,
+ /// possibly including trailing comma.
+ pub(super) fn parse_angle_args(
+ &mut self,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Vec<AngleBracketedArg>> {
+ let mut args = Vec::new();
+ while let Some(arg) = self.parse_angle_arg(ty_generics)? {
+ args.push(arg);
+ if !self.eat(&token::Comma) {
+ if self.check_noexpect(&TokenKind::Semi)
+ && self.look_ahead(1, |t| t.is_ident() || t.is_lifetime())
+ {
+ // Add `>` to the list of expected tokens.
+ self.check(&token::Gt);
+ // Handle `,` to `;` substitution
+ let mut err = self.unexpected::<()>().unwrap_err();
+ self.bump();
+ err.span_suggestion_verbose(
+ self.prev_token.span.until(self.token.span),
+ "use a comma to separate type parameters",
+ ", ",
+ Applicability::MachineApplicable,
+ );
+ err.emit();
+ continue;
+ }
+ if !self.token.kind.should_end_const_arg() {
+ if self.handle_ambiguous_unbraced_const_arg(&mut args)? {
+ // We've managed to (partially) recover, so continue trying to parse
+ // arguments.
+ continue;
+ }
+ }
+ break;
+ }
+ }
+ Ok(args)
+ }
+
+ /// Parses a single argument in the angle arguments `<...>` of a path segment.
+ fn parse_angle_arg(
+ &mut self,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Option<AngleBracketedArg>> {
+ let lo = self.token.span;
+ let arg = self.parse_generic_arg(ty_generics)?;
+ match arg {
+ Some(arg) => {
+ // we are using noexpect here because we first want to find out if either `=` or `:`
+ // is present and then use that info to push the other token onto the tokens list
+ let separated =
+ self.check_noexpect(&token::Colon) || self.check_noexpect(&token::Eq);
+ if separated && (self.check(&token::Colon) | self.check(&token::Eq)) {
+ let arg_span = arg.span();
+ let (binder, ident, gen_args) = match self.get_ident_from_generic_arg(&arg) {
+ Ok(ident_gen_args) => ident_gen_args,
+ Err(()) => return Ok(Some(AngleBracketedArg::Arg(arg))),
+ };
+ if binder.is_some() {
+ // FIXME(compiler-errors): this could be improved by suggesting lifting
+ // this up to the trait, at least before this becomes real syntax.
+ // e.g. `Trait<for<'a> Assoc = Ty>` -> `for<'a> Trait<Assoc = Ty>`
+ return Err(self.struct_span_err(
+ arg_span,
+ "`for<...>` is not allowed on associated type bounds",
+ ));
+ }
+ let kind = if self.eat(&token::Colon) {
+ // Parse associated type constraint bound.
+
+ let bounds = self.parse_generic_bounds(Some(self.prev_token.span))?;
+ AssocConstraintKind::Bound { bounds }
+ } else if self.eat(&token::Eq) {
+ self.parse_assoc_equality_term(ident, self.prev_token.span)?
+ } else {
+ unreachable!();
+ };
+
+ let span = lo.to(self.prev_token.span);
+
+ // Gate associated type bounds, e.g., `Iterator<Item: Ord>`.
+ if let AssocConstraintKind::Bound { .. } = kind {
+ self.sess.gated_spans.gate(sym::associated_type_bounds, span);
+ }
+ let constraint =
+ AssocConstraint { id: ast::DUMMY_NODE_ID, ident, gen_args, kind, span };
+ Ok(Some(AngleBracketedArg::Constraint(constraint)))
+ } else {
+ // we only want to suggest `:` and `=` in contexts where the previous token
+ // is an ident and the current token or the next token is an ident
+ if self.prev_token.is_ident()
+ && (self.token.is_ident() || self.look_ahead(1, |token| token.is_ident()))
+ {
+ self.check(&token::Colon);
+ self.check(&token::Eq);
+ }
+ Ok(Some(AngleBracketedArg::Arg(arg)))
+ }
+ }
+ _ => Ok(None),
+ }
+ }
+
+ /// Parse the term to the right of an associated item equality constraint.
+ /// That is, parse `<term>` in `Item = <term>`.
+ /// Right now, this only admits types in `<term>`.
+ fn parse_assoc_equality_term(
+ &mut self,
+ ident: Ident,
+ eq: Span,
+ ) -> PResult<'a, AssocConstraintKind> {
+ let arg = self.parse_generic_arg(None)?;
+ let span = ident.span.to(self.prev_token.span);
+ let term = match arg {
+ Some(GenericArg::Type(ty)) => ty.into(),
+ Some(GenericArg::Const(c)) => {
+ self.sess.gated_spans.gate(sym::associated_const_equality, span);
+ c.into()
+ }
+ Some(GenericArg::Lifetime(lt)) => {
+ self.struct_span_err(span, "associated lifetimes are not supported")
+ .span_label(lt.ident.span, "the lifetime is given here")
+ .help("if you meant to specify a trait object, write `dyn Trait + 'lifetime`")
+ .emit();
+ self.mk_ty(span, ast::TyKind::Err).into()
+ }
+ None => {
+ let after_eq = eq.shrink_to_hi();
+ let before_next = self.token.span.shrink_to_lo();
+ let mut err = self
+ .struct_span_err(after_eq.to(before_next), "missing type to the right of `=`");
+ if matches!(self.token.kind, token::Comma | token::Gt) {
+ err.span_suggestion(
+ self.sess.source_map().next_point(eq).to(before_next),
+ "to constrain the associated type, add a type after `=`",
+ " TheType",
+ Applicability::HasPlaceholders,
+ );
+ err.span_suggestion(
+ eq.to(before_next),
+ &format!("remove the `=` if `{}` is a type", ident),
+ "",
+ Applicability::MaybeIncorrect,
+ )
+ } else {
+ err.span_label(
+ self.token.span,
+ &format!("expected type, found {}", super::token_descr(&self.token)),
+ )
+ };
+ return Err(err);
+ }
+ };
+ Ok(AssocConstraintKind::Equality { term })
+ }
+
+ /// We do not permit arbitrary expressions as const arguments. They must be one of:
+ /// - An expression surrounded in `{}`.
+ /// - A literal.
+ /// - A numeric literal prefixed by `-`.
+ /// - A single-segment path.
+ pub(super) fn expr_is_valid_const_arg(&self, expr: &P<rustc_ast::Expr>) -> bool {
+ match &expr.kind {
+ ast::ExprKind::Block(_, _) | ast::ExprKind::Lit(_) => true,
+ ast::ExprKind::Unary(ast::UnOp::Neg, expr) => {
+ matches!(expr.kind, ast::ExprKind::Lit(_))
+ }
+ // We can only resolve single-segment paths at the moment, because multi-segment paths
+ // require type-checking: see `visit_generic_arg` in `src/librustc_resolve/late.rs`.
+ ast::ExprKind::Path(None, path)
+ if path.segments.len() == 1 && path.segments[0].args.is_none() =>
+ {
+ true
+ }
+ _ => false,
+ }
+ }
+
+ /// Parse a const argument, e.g. `<3>`. It is assumed the angle brackets will be parsed by
+ /// the caller.
+ pub(super) fn parse_const_arg(&mut self) -> PResult<'a, AnonConst> {
+ // Parse const argument.
+ let value = if let token::OpenDelim(Delimiter::Brace) = self.token.kind {
+ self.parse_block_expr(
+ None,
+ self.token.span,
+ BlockCheckMode::Default,
+ ast::AttrVec::new(),
+ )?
+ } else {
+ self.handle_unambiguous_unbraced_const_arg()?
+ };
+ Ok(AnonConst { id: ast::DUMMY_NODE_ID, value })
+ }
+
+ /// Parse a generic argument in a path segment.
+ /// This does not include constraints, e.g., `Item = u8`, which is handled in `parse_angle_arg`.
+ pub(super) fn parse_generic_arg(
+ &mut self,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, Option<GenericArg>> {
+ let start = self.token.span;
+ let arg = if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
+ // Parse lifetime argument.
+ GenericArg::Lifetime(self.expect_lifetime())
+ } else if self.check_const_arg() {
+ // Parse const argument.
+ GenericArg::Const(self.parse_const_arg()?)
+ } else if self.check_type() {
+ // Parse type argument.
+ let is_const_fn =
+ self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Parenthesis));
+ let mut snapshot = self.create_snapshot_for_diagnostic();
+ match self.parse_ty() {
+ Ok(ty) => GenericArg::Type(ty),
+ Err(err) => {
+ if is_const_fn {
+ match (*snapshot).parse_expr_res(Restrictions::CONST_EXPR, None) {
+ Ok(expr) => {
+ self.restore_snapshot(snapshot);
+ return Ok(Some(self.dummy_const_arg_needs_braces(err, expr.span)));
+ }
+ Err(err) => {
+ err.cancel();
+ }
+ }
+ }
+ // Try to recover from possible `const` arg without braces.
+ return self.recover_const_arg(start, err).map(Some);
+ }
+ }
+ } else if self.token.is_keyword(kw::Const) {
+ return self.recover_const_param_declaration(ty_generics);
+ } else {
+ // Fall back by trying to parse a const-expr expression. If we successfully do so,
+ // then we should report an error that it needs to be wrapped in braces.
+ let snapshot = self.create_snapshot_for_diagnostic();
+ match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
+ Ok(expr) => {
+ return Ok(Some(self.dummy_const_arg_needs_braces(
+ self.struct_span_err(expr.span, "invalid const generic expression"),
+ expr.span,
+ )));
+ }
+ Err(err) => {
+ self.restore_snapshot(snapshot);
+ err.cancel();
+ return Ok(None);
+ }
+ }
+ };
+ Ok(Some(arg))
+ }
+
+ /// Given a arg inside of generics, we try to destructure it as if it were the LHS in
+ /// `LHS = ...`, i.e. an associated type binding.
+ /// This returns (optionally, if they are present) any `for<'a, 'b>` binder args, the
+ /// identifier, and any GAT arguments.
+ fn get_ident_from_generic_arg(
+ &self,
+ gen_arg: &GenericArg,
+ ) -> Result<(Option<Vec<ast::GenericParam>>, Ident, Option<GenericArgs>), ()> {
+ if let GenericArg::Type(ty) = gen_arg {
+ if let ast::TyKind::Path(qself, path) = &ty.kind
+ && qself.is_none()
+ && let [seg] = path.segments.as_slice()
+ {
+ return Ok((None, seg.ident, seg.args.as_deref().cloned()));
+ } else if let ast::TyKind::TraitObject(bounds, ast::TraitObjectSyntax::None) = &ty.kind
+ && let [ast::GenericBound::Trait(trait_ref, ast::TraitBoundModifier::None)] =
+ bounds.as_slice()
+ && let [seg] = trait_ref.trait_ref.path.segments.as_slice()
+ {
+ return Ok((
+ Some(trait_ref.bound_generic_params.clone()),
+ seg.ident,
+ seg.args.as_deref().cloned(),
+ ));
+ }
+ }
+ Err(())
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
new file mode 100644
index 000000000..51bd9d2d3
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -0,0 +1,648 @@
+use super::attr::DEFAULT_INNER_ATTR_FORBIDDEN;
+use super::diagnostics::{AttemptLocalParseRecovery, Error};
+use super::expr::LhsExpr;
+use super::pat::RecoverComma;
+use super::path::PathStyle;
+use super::TrailingToken;
+use super::{
+ AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
+};
+use crate::maybe_whole;
+
+use rustc_ast as ast;
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, TokenKind};
+use rustc_ast::util::classify;
+use rustc_ast::{AttrStyle, AttrVec, Attribute, LocalKind, MacCall, MacCallStmt, MacStmtStyle};
+use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, HasAttrs, Local, Stmt};
+use rustc_ast::{StmtKind, DUMMY_NODE_ID};
+use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
+use rustc_span::source_map::{BytePos, Span};
+use rustc_span::symbol::{kw, sym};
+
+use std::mem;
+
+impl<'a> Parser<'a> {
+ /// Parses a statement. This stops just before trailing semicolons on everything but items.
+ /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
+ // Public for rustfmt usage.
+ pub fn parse_stmt(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<Stmt>> {
+ Ok(self.parse_stmt_without_recovery(false, force_collect).unwrap_or_else(|mut e| {
+ e.emit();
+ self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
+ None
+ }))
+ }
+
+ /// If `force_capture` is true, forces collection of tokens regardless of whether
+ /// or not we have attributes
+ pub(crate) fn parse_stmt_without_recovery(
+ &mut self,
+ capture_semi: bool,
+ force_collect: ForceCollect,
+ ) -> PResult<'a, Option<Stmt>> {
+ let attrs = self.parse_outer_attributes()?;
+ let lo = self.token.span;
+
+ // 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 && let token::NtStmt(stmt) = &**nt {
+ let mut stmt = stmt.clone();
+ self.bump();
+ stmt.visit_attrs(|stmt_attrs| {
+ attrs.prepend_to_nt_inner(stmt_attrs);
+ });
+ return Ok(Some(stmt.into_inner()));
+ }
+
+ Ok(Some(if self.token.is_keyword(kw::Let) {
+ self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
+ } else if self.is_kw_followed_by_ident(kw::Mut) {
+ self.recover_stmt_local(lo, attrs, "missing keyword", "let mut")?
+ } else if self.is_kw_followed_by_ident(kw::Auto) {
+ self.bump(); // `auto`
+ let msg = "write `let` instead of `auto` to introduce a new variable";
+ self.recover_stmt_local(lo, attrs, msg, "let")?
+ } else if self.is_kw_followed_by_ident(sym::var) {
+ self.bump(); // `var`
+ let msg = "write `let` instead of `var` to introduce a new variable";
+ self.recover_stmt_local(lo, attrs, msg, "let")?
+ } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
+ // We have avoided contextual keywords like `union`, items with `crate` visibility,
+ // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
+ // that starts like a path (1 token), but it fact not a path.
+ // Also, we avoid stealing syntax from `parse_item_`.
+ if force_collect == ForceCollect::Yes {
+ self.collect_tokens_no_attrs(|this| this.parse_stmt_path_start(lo, attrs))
+ } else {
+ self.parse_stmt_path_start(lo, attrs)
+ }?
+ } else if let Some(item) = self.parse_item_common(
+ attrs.clone(),
+ false,
+ true,
+ FnParseMode { req_name: |_| true, req_body: true },
+ force_collect,
+ )? {
+ // FIXME: Bad copy of attrs
+ self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
+ } else if self.eat(&token::Semi) {
+ // Do not attempt to parse an expression if we're done here.
+ self.error_outer_attrs(&attrs.take_for_recovery());
+ self.mk_stmt(lo, StmtKind::Empty)
+ } else if self.token != token::CloseDelim(Delimiter::Brace) {
+ // Remainder are line-expr stmts.
+ let e = if force_collect == ForceCollect::Yes {
+ self.collect_tokens_no_attrs(|this| {
+ this.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
+ })
+ } else {
+ self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs))
+ }?;
+ if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
+ let bl = self.parse_block()?;
+ // Destructuring assignment ... else.
+ // This is not allowed, but point it out in a nice way.
+ let mut err = self.struct_span_err(
+ e.span.to(bl.span),
+ "<assignment> ... else { ... } is not allowed",
+ );
+ err.emit();
+ }
+ self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
+ } else {
+ self.error_outer_attrs(&attrs.take_for_recovery());
+ return Ok(None);
+ }))
+ }
+
+ fn parse_stmt_path_start(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
+ let stmt = self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let path = this.parse_path(PathStyle::Expr)?;
+
+ if this.eat(&token::Not) {
+ let stmt_mac = this.parse_stmt_mac(lo, attrs.into(), path)?;
+ if this.token == token::Semi {
+ return Ok((stmt_mac, TrailingToken::Semi));
+ } else {
+ return Ok((stmt_mac, TrailingToken::None));
+ }
+ }
+
+ let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
+ this.parse_struct_expr(None, path, AttrVec::new(), true)?
+ } else {
+ let hi = this.prev_token.span;
+ this.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new())
+ };
+
+ let expr = this.with_res(Restrictions::STMT_EXPR, |this| {
+ this.parse_dot_or_call_expr_with(expr, lo, attrs)
+ })?;
+ // `DUMMY_SP` will get overwritten later in this function
+ Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), TrailingToken::None))
+ })?;
+
+ if let StmtKind::Expr(expr) = stmt.kind {
+ // Perform this outside of the `collect_tokens_trailing_token` closure,
+ // since our outer attributes do not apply to this part of the expression
+ let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
+ this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
+ })?;
+ Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
+ } else {
+ Ok(stmt)
+ }
+ }
+
+ /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`.
+ /// At this point, the `!` token after the path has already been eaten.
+ fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> {
+ let args = self.parse_mac_args()?;
+ let delim = args.delim();
+ let hi = self.prev_token.span;
+
+ let style = match delim {
+ Some(Delimiter::Brace) => MacStmtStyle::Braces,
+ Some(_) => MacStmtStyle::NoBraces,
+ None => unreachable!(),
+ };
+
+ let mac = MacCall { path, args, prior_type_ascription: self.last_type_ascription };
+
+ let kind = if (style == MacStmtStyle::Braces
+ && self.token != token::Dot
+ && self.token != token::Question)
+ || self.token == token::Semi
+ || self.token == token::Eof
+ {
+ StmtKind::MacCall(P(MacCallStmt { mac, style, attrs, tokens: None }))
+ } else {
+ // Since none of the above applied, this is an expression statement macro.
+ let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac), AttrVec::new());
+ let e = self.maybe_recover_from_bad_qpath(e)?;
+ let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
+ let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
+ StmtKind::Expr(e)
+ };
+ Ok(self.mk_stmt(lo.to(hi), kind))
+ }
+
+ /// Error on outer attributes in this context.
+ /// Also error if the previous token was a doc comment.
+ fn error_outer_attrs(&self, attrs: &[Attribute]) {
+ if let [.., last] = attrs {
+ if last.is_doc_comment() {
+ self.span_err(last.span, Error::UselessDocComment).emit();
+ } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
+ self.struct_span_err(last.span, "expected statement after outer attribute").emit();
+ }
+ }
+ }
+
+ fn recover_stmt_local(
+ &mut self,
+ lo: Span,
+ attrs: AttrWrapper,
+ msg: &str,
+ sugg: &str,
+ ) -> PResult<'a, Stmt> {
+ let stmt = self.recover_local_after_let(lo, attrs)?;
+ self.struct_span_err(lo, "invalid variable declaration")
+ .span_suggestion(lo, msg, sugg, Applicability::MachineApplicable)
+ .emit();
+ Ok(stmt)
+ }
+
+ fn parse_local_mk(
+ &mut self,
+ lo: Span,
+ attrs: AttrWrapper,
+ capture_semi: bool,
+ force_collect: ForceCollect,
+ ) -> PResult<'a, Stmt> {
+ self.collect_tokens_trailing_token(attrs, force_collect, |this, attrs| {
+ this.expect_keyword(kw::Let)?;
+ let local = this.parse_local(attrs.into())?;
+ let trailing = if capture_semi && this.token.kind == token::Semi {
+ TrailingToken::Semi
+ } else {
+ TrailingToken::None
+ };
+ Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)), trailing))
+ })
+ }
+
+ fn recover_local_after_let(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
+ self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
+ let local = this.parse_local(attrs.into())?;
+ // FIXME - maybe capture semicolon in recovery?
+ Ok((
+ this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
+ TrailingToken::None,
+ ))
+ })
+ }
+
+ /// Parses a local variable declaration.
+ fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
+ let lo = self.prev_token.span;
+ let (pat, colon) = self.parse_pat_before_ty(None, RecoverComma::Yes, "`let` bindings")?;
+
+ let (err, ty) = if colon {
+ // Save the state of the parser before parsing type normally, in case there is a `:`
+ // instead of an `=` typo.
+ let parser_snapshot_before_type = self.clone();
+ let colon_sp = self.prev_token.span;
+ match self.parse_ty() {
+ Ok(ty) => (None, Some(ty)),
+ Err(mut err) => {
+ if let Ok(snip) = self.span_to_snippet(pat.span) {
+ err.span_label(pat.span, format!("while parsing the type for `{}`", snip));
+ }
+ // we use noexpect here because we don't actually expect Eq to be here
+ // but we are still checking for it in order to be able to handle it if
+ // it is there
+ let err = if self.check_noexpect(&token::Eq) {
+ err.emit();
+ None
+ } else {
+ // Rewind to before attempting to parse the type and continue parsing.
+ let parser_snapshot_after_type =
+ mem::replace(self, parser_snapshot_before_type);
+ Some((parser_snapshot_after_type, colon_sp, err))
+ };
+ (err, None)
+ }
+ }
+ } else {
+ (None, None)
+ };
+ let init = match (self.parse_initializer(err.is_some()), err) {
+ (Ok(init), None) => {
+ // init parsed, ty parsed
+ init
+ }
+ (Ok(init), Some((_, colon_sp, mut err))) => {
+ // init parsed, ty error
+ // Could parse the type as if it were the initializer, it is likely there was a
+ // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
+ err.span_suggestion_short(
+ colon_sp,
+ "use `=` if you meant to assign",
+ " =",
+ Applicability::MachineApplicable,
+ );
+ err.emit();
+ // As this was parsed successfully, continue as if the code has been fixed for the
+ // rest of the file. It will still fail due to the emitted error, but we avoid
+ // extra noise.
+ init
+ }
+ (Err(init_err), Some((snapshot, _, ty_err))) => {
+ // init error, ty error
+ init_err.cancel();
+ // Couldn't parse the type nor the initializer, only raise the type error and
+ // return to the parser state before parsing the type as the initializer.
+ // let x: <parse_error>;
+ *self = snapshot;
+ return Err(ty_err);
+ }
+ (Err(err), None) => {
+ // init error, ty parsed
+ // Couldn't parse the initializer and we're not attempting to recover a failed
+ // parse of the type, return the error.
+ return Err(err);
+ }
+ };
+ let kind = match init {
+ None => LocalKind::Decl,
+ Some(init) => {
+ if self.eat_keyword(kw::Else) {
+ if self.token.is_keyword(kw::If) {
+ // `let...else if`. Emit the same error that `parse_block()` would,
+ // but explicitly point out that this pattern is not allowed.
+ let msg = "conditional `else if` is not supported for `let...else`";
+ return Err(self.error_block_no_opening_brace_msg(msg));
+ }
+ let els = self.parse_block()?;
+ self.check_let_else_init_bool_expr(&init);
+ self.check_let_else_init_trailing_brace(&init);
+ LocalKind::InitElse(init, els)
+ } else {
+ LocalKind::Init(init)
+ }
+ }
+ };
+ let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span };
+ Ok(P(ast::Local { ty, pat, kind, id: DUMMY_NODE_ID, span: lo.to(hi), attrs, tokens: None }))
+ }
+
+ fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
+ if let ast::ExprKind::Binary(op, ..) = init.kind {
+ if op.node.lazy() {
+ let suggs = vec![
+ (init.span.shrink_to_lo(), "(".to_string()),
+ (init.span.shrink_to_hi(), ")".to_string()),
+ ];
+ self.struct_span_err(
+ init.span,
+ &format!(
+ "a `{}` expression cannot be directly assigned in `let...else`",
+ op.node.to_string()
+ ),
+ )
+ .multipart_suggestion(
+ "wrap the expression in parentheses",
+ suggs,
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+ }
+ }
+
+ fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
+ if let Some(trailing) = classify::expr_trailing_brace(init) {
+ let err_span = trailing.span.with_lo(trailing.span.hi() - BytePos(1));
+ let suggs = vec![
+ (trailing.span.shrink_to_lo(), "(".to_string()),
+ (trailing.span.shrink_to_hi(), ")".to_string()),
+ ];
+ self.struct_span_err(
+ err_span,
+ "right curly brace `}` before `else` in a `let...else` statement not allowed",
+ )
+ .multipart_suggestion(
+ "try wrapping the expression in parentheses",
+ suggs,
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+ }
+
+ /// Parses the RHS of a local variable declaration (e.g., `= 14;`).
+ fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
+ let eq_consumed = match self.token.kind {
+ token::BinOpEq(..) => {
+ // Recover `let x <op>= 1` as `let x = 1`
+ self.struct_span_err(
+ self.token.span,
+ "can't reassign to an uninitialized variable",
+ )
+ .span_suggestion_short(
+ self.token.span,
+ "initialize the variable",
+ "=",
+ Applicability::MaybeIncorrect,
+ )
+ .help("if you meant to overwrite, remove the `let` binding")
+ .emit();
+ self.bump();
+ true
+ }
+ _ => self.eat(&token::Eq),
+ };
+
+ Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None })
+ }
+
+ /// Parses a block. No inner attributes are allowed.
+ pub(super) fn parse_block(&mut self) -> PResult<'a, P<Block>> {
+ let (attrs, block) = self.parse_inner_attrs_and_block()?;
+ if let [.., last] = &*attrs {
+ self.error_on_forbidden_inner_attr(last.span, DEFAULT_INNER_ATTR_FORBIDDEN);
+ }
+ Ok(block)
+ }
+
+ fn error_block_no_opening_brace_msg(
+ &mut self,
+ msg: &str,
+ ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+ let sp = self.token.span;
+ let mut e = self.struct_span_err(sp, msg);
+ let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon;
+
+ // Check to see if the user has written something like
+ //
+ // if (cond)
+ // bar;
+ //
+ // which is valid in other languages, but not Rust.
+ match self.parse_stmt_without_recovery(false, ForceCollect::No) {
+ // If the next token is an open brace, e.g., we have:
+ //
+ // if expr other_expr {
+ // ^ ^ ^- lookahead(1) is a brace
+ // | |- current token is not "else"
+ // |- (statement we just parsed)
+ //
+ // the place-inside-a-block suggestion would be more likely wrong than right.
+ //
+ // FIXME(compiler-errors): this should probably parse an arbitrary expr and not
+ // just lookahead one token, so we can see if there's a brace after _that_,
+ // since we want to protect against:
+ // `if 1 1 + 1 {` being suggested as `if { 1 } 1 + 1 {`
+ // + +
+ Ok(Some(_))
+ if (!self.token.is_keyword(kw::Else)
+ && self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)))
+ || do_not_suggest_help => {}
+ // Do not suggest `if foo println!("") {;}` (as would be seen in test for #46836).
+ Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}
+ Ok(Some(stmt)) => {
+ let stmt_own_line = self.sess.source_map().is_line_before_span_empty(sp);
+ let stmt_span = if stmt_own_line && self.eat(&token::Semi) {
+ // Expand the span to include the semicolon.
+ stmt.span.with_hi(self.prev_token.span.hi())
+ } else {
+ stmt.span
+ };
+ e.multipart_suggestion(
+ "try placing this code inside a block",
+ vec![
+ (stmt_span.shrink_to_lo(), "{ ".to_string()),
+ (stmt_span.shrink_to_hi(), " }".to_string()),
+ ],
+ // Speculative; has been misleading in the past (#46836).
+ Applicability::MaybeIncorrect,
+ );
+ }
+ Err(e) => {
+ self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
+ e.cancel();
+ }
+ _ => {}
+ }
+ e.span_label(sp, "expected `{`");
+ e
+ }
+
+ fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
+ let tok = super::token_descr(&self.token);
+ let msg = format!("expected `{{`, found {}", tok);
+ Err(self.error_block_no_opening_brace_msg(&msg))
+ }
+
+ /// Parses a block. Inner attributes are allowed.
+ pub(super) fn parse_inner_attrs_and_block(
+ &mut self,
+ ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
+ self.parse_block_common(self.token.span, BlockCheckMode::Default)
+ }
+
+ /// Parses a block. Inner attributes are allowed.
+ pub(super) fn parse_block_common(
+ &mut self,
+ lo: Span,
+ blk_mode: BlockCheckMode,
+ ) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
+ maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
+
+ self.maybe_recover_unexpected_block_label();
+ if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
+ return self.error_block_no_opening_brace();
+ }
+
+ let attrs = self.parse_inner_attributes()?;
+ let tail = match self.maybe_suggest_struct_literal(lo, blk_mode) {
+ Some(tail) => tail?,
+ None => self.parse_block_tail(lo, blk_mode, AttemptLocalParseRecovery::Yes)?,
+ };
+ Ok((attrs, tail))
+ }
+
+ /// Parses the rest of a block expression or function body.
+ /// Precondition: already parsed the '{'.
+ pub(crate) fn parse_block_tail(
+ &mut self,
+ lo: Span,
+ s: BlockCheckMode,
+ recover: AttemptLocalParseRecovery,
+ ) -> PResult<'a, P<Block>> {
+ let mut stmts = vec![];
+ while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
+ if self.token == token::Eof {
+ break;
+ }
+ let stmt = match self.parse_full_stmt(recover) {
+ Err(mut err) if recover.yes() => {
+ self.maybe_annotate_with_ascription(&mut err, false);
+ err.emit();
+ self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
+ Some(self.mk_stmt_err(self.token.span))
+ }
+ Ok(stmt) => stmt,
+ Err(err) => return Err(err),
+ };
+ if let Some(stmt) = stmt {
+ stmts.push(stmt);
+ } else {
+ // Found only `;` or `}`.
+ continue;
+ };
+ }
+ Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
+ }
+
+ /// Parses a statement, including the trailing semicolon.
+ pub fn parse_full_stmt(
+ &mut self,
+ recover: AttemptLocalParseRecovery,
+ ) -> PResult<'a, Option<Stmt>> {
+ // Skip looking for a trailing semicolon when we have an interpolated statement.
+ maybe_whole!(self, NtStmt, |x| Some(x.into_inner()));
+
+ let Some(mut stmt) = self.parse_stmt_without_recovery(true, ForceCollect::No)? else {
+ return Ok(None);
+ };
+
+ let mut eat_semi = true;
+ match stmt.kind {
+ // Expression without semicolon.
+ StmtKind::Expr(ref mut expr)
+ if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>
+ {
+ // Just check for errors and recover; do not eat semicolon yet.
+ if let Err(mut e) =
+ self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)])
+ {
+ if let TokenKind::DocComment(..) = self.token.kind {
+ if let Ok(snippet) = self.span_to_snippet(self.token.span) {
+ let sp = self.token.span;
+ let marker = &snippet[..3];
+ let (comment_marker, doc_comment_marker) = marker.split_at(2);
+
+ e.span_suggestion(
+ sp.with_hi(sp.lo() + BytePos(marker.len() as u32)),
+ &format!(
+ "add a space before `{}` to use a regular comment",
+ doc_comment_marker,
+ ),
+ format!("{} {}", comment_marker, doc_comment_marker),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ if let Err(mut e) =
+ self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
+ {
+ if recover.no() {
+ return Err(e);
+ }
+ e.emit();
+ self.recover_stmt();
+ }
+ // Don't complain about type errors in body tail after parse error (#57383).
+ let sp = expr.span.to(self.prev_token.span);
+ *expr = self.mk_expr_err(sp);
+ }
+ }
+ StmtKind::Expr(_) | StmtKind::MacCall(_) => {}
+ StmtKind::Local(ref mut local) if let Err(e) = self.expect_semi() => {
+ // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
+ match &mut local.kind {
+ LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
+ self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
+ // We found `foo<bar, baz>`, have we fully recovered?
+ self.expect_semi()?;
+ }
+ LocalKind::Decl => return Err(e),
+ }
+ eat_semi = false;
+ }
+ StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => eat_semi = false,
+ }
+
+ if eat_semi && self.eat(&token::Semi) {
+ stmt = stmt.add_trailing_semicolon();
+ }
+ stmt.span = stmt.span.to(self.prev_token.span);
+ Ok(Some(stmt))
+ }
+
+ pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
+ P(Block {
+ stmts,
+ id: DUMMY_NODE_ID,
+ rules,
+ span,
+ tokens: None,
+ could_be_bare_literal: false,
+ })
+ }
+
+ pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
+ Stmt { id: DUMMY_NODE_ID, kind, span }
+ }
+
+ pub(super) fn mk_stmt_err(&self, span: Span) -> Stmt {
+ self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span)))
+ }
+
+ pub(super) fn mk_block_err(&self, span: Span) -> P<Block> {
+ self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span)
+ }
+}
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
new file mode 100644
index 000000000..31b40a83e
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -0,0 +1,891 @@
+use super::{Parser, PathStyle, TokenType};
+
+use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::{
+ self as ast, BareFnTy, FnRetTy, GenericBound, GenericBounds, GenericParam, Generics, Lifetime,
+ MacCall, MutTy, Mutability, PolyTraitRef, TraitBoundModifier, TraitObjectSyntax, Ty, TyKind,
+};
+use rustc_errors::{pluralize, struct_span_err, Applicability, PResult};
+use rustc_span::source_map::Span;
+use rustc_span::symbol::{kw, sym};
+
+/// Any `?` or `~const` modifiers that appear at the start of a bound.
+struct BoundModifiers {
+ /// `?Trait`.
+ maybe: Option<Span>,
+
+ /// `~const Trait`.
+ maybe_const: Option<Span>,
+}
+
+impl BoundModifiers {
+ fn to_trait_bound_modifier(&self) -> TraitBoundModifier {
+ match (self.maybe, self.maybe_const) {
+ (None, None) => TraitBoundModifier::None,
+ (Some(_), None) => TraitBoundModifier::Maybe,
+ (None, Some(_)) => TraitBoundModifier::MaybeConst,
+ (Some(_), Some(_)) => TraitBoundModifier::MaybeConstMaybe,
+ }
+ }
+}
+
+#[derive(Copy, Clone, PartialEq)]
+pub(super) enum AllowPlus {
+ Yes,
+ No,
+}
+
+#[derive(PartialEq)]
+pub(super) enum RecoverQPath {
+ Yes,
+ No,
+}
+
+pub(super) enum RecoverQuestionMark {
+ Yes,
+ No,
+}
+
+/// Signals whether parsing a type should recover `->`.
+///
+/// More specifically, when parsing a function like:
+/// ```compile_fail
+/// fn foo() => u8 { 0 }
+/// fn bar(): u8 { 0 }
+/// ```
+/// The compiler will try to recover interpreting `foo() => u8` as `foo() -> u8` when calling
+/// `parse_ty` with anything except `RecoverReturnSign::No`, and it will try to recover `bar(): u8`
+/// as `bar() -> u8` when passing `RecoverReturnSign::Yes` to `parse_ty`
+#[derive(Copy, Clone, PartialEq)]
+pub(super) enum RecoverReturnSign {
+ Yes,
+ OnlyFatArrow,
+ No,
+}
+
+impl RecoverReturnSign {
+ /// [RecoverReturnSign::Yes] allows for recovering `fn foo() => u8` and `fn foo(): u8`,
+ /// [RecoverReturnSign::OnlyFatArrow] allows for recovering only `fn foo() => u8` (recovering
+ /// colons can cause problems when parsing where clauses), and
+ /// [RecoverReturnSign::No] doesn't allow for any recovery of the return type arrow
+ fn can_recover(self, token: &TokenKind) -> bool {
+ match self {
+ Self::Yes => matches!(token, token::FatArrow | token::Colon),
+ Self::OnlyFatArrow => matches!(token, token::FatArrow),
+ Self::No => false,
+ }
+ }
+}
+
+// Is `...` (`CVarArgs`) legal at this level of type parsing?
+#[derive(PartialEq)]
+enum AllowCVariadic {
+ Yes,
+ No,
+}
+
+/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
+/// `IDENT<<u8 as Trait>::AssocTy>`.
+///
+/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
+/// that `IDENT` is not the ident of a fn trait.
+fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
+ t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl)
+}
+
+impl<'a> Parser<'a> {
+ /// Parses a type.
+ pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::Yes,
+ AllowCVariadic::No,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ None,
+ RecoverQuestionMark::Yes,
+ )
+ }
+
+ pub(super) fn parse_ty_with_generics_recovery(
+ &mut self,
+ ty_params: &Generics,
+ ) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::Yes,
+ AllowCVariadic::No,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ Some(ty_params),
+ RecoverQuestionMark::Yes,
+ )
+ }
+
+ /// Parse a type suitable for a function or function pointer parameter.
+ /// The difference from `parse_ty` is that this version allows `...`
+ /// (`CVarArgs`) at the top level of the type.
+ pub(super) fn parse_ty_for_param(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::Yes,
+ AllowCVariadic::Yes,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ None,
+ RecoverQuestionMark::Yes,
+ )
+ }
+
+ /// Parses a type in restricted contexts where `+` is not permitted.
+ ///
+ /// Example 1: `&'a TYPE`
+ /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
+ /// Example 2: `value1 as TYPE + value2`
+ /// `+` is prohibited to avoid interactions with expression grammar.
+ pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::No,
+ AllowCVariadic::No,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ None,
+ RecoverQuestionMark::Yes,
+ )
+ }
+
+ /// Parses a type following an `as` cast. Similar to `parse_ty_no_plus`, but signaling origin
+ /// for better diagnostics involving `?`.
+ pub(super) fn parse_as_cast_ty(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::No,
+ AllowCVariadic::No,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ None,
+ RecoverQuestionMark::No,
+ )
+ }
+
+ pub(super) fn parse_no_question_mark_recover(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::Yes,
+ AllowCVariadic::No,
+ RecoverQPath::Yes,
+ RecoverReturnSign::Yes,
+ None,
+ RecoverQuestionMark::No,
+ )
+ }
+
+ /// Parse a type without recovering `:` as `->` to avoid breaking code such as `where fn() : for<'a>`
+ pub(super) fn parse_ty_for_where_clause(&mut self) -> PResult<'a, P<Ty>> {
+ self.parse_ty_common(
+ AllowPlus::Yes,
+ AllowCVariadic::Yes,
+ RecoverQPath::Yes,
+ RecoverReturnSign::OnlyFatArrow,
+ None,
+ RecoverQuestionMark::Yes,
+ )
+ }
+
+ /// Parses an optional return type `[ -> TY ]` in a function declaration.
+ pub(super) fn parse_ret_ty(
+ &mut self,
+ allow_plus: AllowPlus,
+ recover_qpath: RecoverQPath,
+ recover_return_sign: RecoverReturnSign,
+ ) -> PResult<'a, FnRetTy> {
+ Ok(if self.eat(&token::RArrow) {
+ // FIXME(Centril): Can we unconditionally `allow_plus`?
+ let ty = self.parse_ty_common(
+ allow_plus,
+ AllowCVariadic::No,
+ recover_qpath,
+ recover_return_sign,
+ None,
+ RecoverQuestionMark::Yes,
+ )?;
+ FnRetTy::Ty(ty)
+ } else if recover_return_sign.can_recover(&self.token.kind) {
+ // Don't `eat` to prevent `=>` from being added as an expected token which isn't
+ // actually expected and could only confuse users
+ self.bump();
+ self.struct_span_err(self.prev_token.span, "return types are denoted using `->`")
+ .span_suggestion_short(
+ self.prev_token.span,
+ "use `->` instead",
+ "->",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ let ty = self.parse_ty_common(
+ allow_plus,
+ AllowCVariadic::No,
+ recover_qpath,
+ recover_return_sign,
+ None,
+ RecoverQuestionMark::Yes,
+ )?;
+ FnRetTy::Ty(ty)
+ } else {
+ FnRetTy::Default(self.token.span.shrink_to_lo())
+ })
+ }
+
+ fn parse_ty_common(
+ &mut self,
+ allow_plus: AllowPlus,
+ allow_c_variadic: AllowCVariadic,
+ recover_qpath: RecoverQPath,
+ recover_return_sign: RecoverReturnSign,
+ ty_generics: Option<&Generics>,
+ recover_question_mark: RecoverQuestionMark,
+ ) -> PResult<'a, P<Ty>> {
+ let allow_qpath_recovery = recover_qpath == RecoverQPath::Yes;
+ maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
+ maybe_whole!(self, NtTy, |x| x);
+
+ let lo = self.token.span;
+ let mut impl_dyn_multi = false;
+ let kind = if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+ self.parse_ty_tuple_or_parens(lo, allow_plus)?
+ } else if self.eat(&token::Not) {
+ // Never type `!`
+ TyKind::Never
+ } else if self.eat(&token::BinOp(token::Star)) {
+ self.parse_ty_ptr()?
+ } else if self.eat(&token::OpenDelim(Delimiter::Bracket)) {
+ self.parse_array_or_slice_ty()?
+ } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
+ // Reference
+ self.expect_and()?;
+ self.parse_borrowed_pointee()?
+ } else if self.eat_keyword_noexpect(kw::Typeof) {
+ self.parse_typeof_ty()?
+ } else if self.eat_keyword(kw::Underscore) {
+ // A type to be inferred `_`
+ TyKind::Infer
+ } else if self.check_fn_front_matter(false) {
+ // Function pointer type
+ self.parse_ty_bare_fn(lo, Vec::new(), recover_return_sign)?
+ } else if self.check_keyword(kw::For) {
+ // Function pointer type or bound list (trait object type) starting with a poly-trait.
+ // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
+ // `for<'lt> Trait1<'lt> + Trait2 + 'a`
+ let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+ if self.check_fn_front_matter(false) {
+ self.parse_ty_bare_fn(lo, lifetime_defs, recover_return_sign)?
+ } else {
+ let path = self.parse_path(PathStyle::Type)?;
+ let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
+ self.parse_remaining_bounds_path(lifetime_defs, path, lo, parse_plus)?
+ }
+ } else if self.eat_keyword(kw::Impl) {
+ self.parse_impl_ty(&mut impl_dyn_multi)?
+ } else if self.is_explicit_dyn_type() {
+ self.parse_dyn_ty(&mut impl_dyn_multi)?
+ } else if self.eat_lt() {
+ // Qualified path
+ let (qself, path) = self.parse_qpath(PathStyle::Type)?;
+ TyKind::Path(Some(qself), path)
+ } else if self.check_path() {
+ self.parse_path_start_ty(lo, allow_plus, ty_generics)?
+ } else if self.can_begin_bound() {
+ self.parse_bare_trait_object(lo, allow_plus)?
+ } else if self.eat(&token::DotDotDot) {
+ if allow_c_variadic == AllowCVariadic::Yes {
+ TyKind::CVarArgs
+ } else {
+ // FIXME(Centril): Should we just allow `...` syntactically
+ // anywhere in a type and use semantic restrictions instead?
+ self.error_illegal_c_varadic_ty(lo);
+ TyKind::Err
+ }
+ } else {
+ let msg = format!("expected type, found {}", super::token_descr(&self.token));
+ let mut err = self.struct_span_err(self.token.span, &msg);
+ err.span_label(self.token.span, "expected type");
+ self.maybe_annotate_with_ascription(&mut err, true);
+ return Err(err);
+ };
+
+ let span = lo.to(self.prev_token.span);
+ let mut ty = self.mk_ty(span, kind);
+
+ // Try to recover from use of `+` with incorrect priority.
+ if matches!(allow_plus, AllowPlus::Yes) {
+ self.maybe_recover_from_bad_type_plus(&ty)?;
+ } else {
+ self.maybe_report_ambiguous_plus(impl_dyn_multi, &ty);
+ }
+ if let RecoverQuestionMark::Yes = recover_question_mark {
+ ty = self.maybe_recover_from_question_mark(ty);
+ }
+ if allow_qpath_recovery { self.maybe_recover_from_bad_qpath(ty) } else { Ok(ty) }
+ }
+
+ /// Parses either:
+ /// - `(TYPE)`, a parenthesized type.
+ /// - `(TYPE,)`, a tuple with a single field of type TYPE.
+ fn parse_ty_tuple_or_parens(&mut self, lo: Span, allow_plus: AllowPlus) -> PResult<'a, TyKind> {
+ let mut trailing_plus = false;
+ let (ts, trailing) = self.parse_paren_comma_seq(|p| {
+ let ty = p.parse_ty()?;
+ trailing_plus = p.prev_token.kind == TokenKind::BinOp(token::Plus);
+ Ok(ty)
+ })?;
+
+ if ts.len() == 1 && !trailing {
+ let ty = ts.into_iter().next().unwrap().into_inner();
+ let maybe_bounds = allow_plus == AllowPlus::Yes && self.token.is_like_plus();
+ match ty.kind {
+ // `(TY_BOUND_NOPAREN) + BOUND + ...`.
+ TyKind::Path(None, path) if maybe_bounds => {
+ self.parse_remaining_bounds_path(Vec::new(), path, lo, true)
+ }
+ TyKind::TraitObject(bounds, TraitObjectSyntax::None)
+ if maybe_bounds && bounds.len() == 1 && !trailing_plus =>
+ {
+ self.parse_remaining_bounds(bounds, true)
+ }
+ // `(TYPE)`
+ _ => Ok(TyKind::Paren(P(ty))),
+ }
+ } else {
+ Ok(TyKind::Tup(ts))
+ }
+ }
+
+ fn parse_bare_trait_object(&mut self, lo: Span, allow_plus: AllowPlus) -> PResult<'a, TyKind> {
+ let lt_no_plus = self.check_lifetime() && !self.look_ahead(1, |t| t.is_like_plus());
+ let bounds = self.parse_generic_bounds_common(allow_plus, None)?;
+ if lt_no_plus {
+ self.struct_span_err(lo, "lifetime in trait object type must be followed by `+`")
+ .emit();
+ }
+ Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
+ }
+
+ fn parse_remaining_bounds_path(
+ &mut self,
+ generic_params: Vec<GenericParam>,
+ path: ast::Path,
+ lo: Span,
+ parse_plus: bool,
+ ) -> PResult<'a, TyKind> {
+ let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_token.span));
+ let bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
+ self.parse_remaining_bounds(bounds, parse_plus)
+ }
+
+ /// Parse the remainder of a bare trait object type given an already parsed list.
+ fn parse_remaining_bounds(
+ &mut self,
+ mut bounds: GenericBounds,
+ plus: bool,
+ ) -> PResult<'a, TyKind> {
+ if plus {
+ self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
+ bounds.append(&mut self.parse_generic_bounds(Some(self.prev_token.span))?);
+ }
+ Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
+ }
+
+ /// Parses a raw pointer type: `*[const | mut] $type`.
+ fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> {
+ let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {
+ let span = self.prev_token.span;
+ let msg = "expected mut or const in raw pointer type";
+ self.struct_span_err(span, msg)
+ .span_label(span, msg)
+ .help("use `*mut T` or `*const T` as appropriate")
+ .emit();
+ Mutability::Not
+ });
+ let ty = self.parse_ty_no_plus()?;
+ Ok(TyKind::Ptr(MutTy { ty, mutbl }))
+ }
+
+ /// Parses an array (`[TYPE; EXPR]`) or slice (`[TYPE]`) type.
+ /// The opening `[` bracket is already eaten.
+ fn parse_array_or_slice_ty(&mut self) -> PResult<'a, TyKind> {
+ let elt_ty = match self.parse_ty() {
+ Ok(ty) => ty,
+ Err(mut err)
+ if self.look_ahead(1, |t| t.kind == token::CloseDelim(Delimiter::Bracket))
+ | self.look_ahead(1, |t| t.kind == token::Semi) =>
+ {
+ // Recover from `[LIT; EXPR]` and `[LIT]`
+ self.bump();
+ err.emit();
+ self.mk_ty(self.prev_token.span, TyKind::Err)
+ }
+ Err(err) => return Err(err),
+ };
+
+ let ty = if self.eat(&token::Semi) {
+ let mut length = self.parse_anon_const_expr()?;
+ if let Err(e) = self.expect(&token::CloseDelim(Delimiter::Bracket)) {
+ // Try to recover from `X<Y, ...>` when `X::<Y, ...>` works
+ self.check_mistyped_turbofish_with_multiple_type_params(e, &mut length.value)?;
+ self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+ }
+ TyKind::Array(elt_ty, length)
+ } else {
+ self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+ TyKind::Slice(elt_ty)
+ };
+
+ Ok(ty)
+ }
+
+ fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
+ let and_span = self.prev_token.span;
+ let mut opt_lifetime =
+ if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
+ let mut mutbl = self.parse_mutability();
+ if self.token.is_lifetime() && mutbl == Mutability::Mut && opt_lifetime.is_none() {
+ // A lifetime is invalid here: it would be part of a bare trait bound, which requires
+ // it to be followed by a plus, but we disallow plus in the pointee type.
+ // So we can handle this case as an error here, and suggest `'a mut`.
+ // If there *is* a plus next though, handling the error later provides better suggestions
+ // (like adding parentheses)
+ if !self.look_ahead(1, |t| t.is_like_plus()) {
+ let lifetime_span = self.token.span;
+ let span = and_span.to(lifetime_span);
+
+ let mut err = self.struct_span_err(span, "lifetime must precede `mut`");
+ if let Ok(lifetime_src) = self.span_to_snippet(lifetime_span) {
+ err.span_suggestion(
+ span,
+ "place the lifetime before `mut`",
+ format!("&{} mut", lifetime_src),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ err.emit();
+
+ opt_lifetime = Some(self.expect_lifetime());
+ }
+ } else if self.token.is_keyword(kw::Dyn)
+ && mutbl == Mutability::Not
+ && self.look_ahead(1, |t| t.is_keyword(kw::Mut))
+ {
+ // We have `&dyn mut ...`, which is invalid and should be `&mut dyn ...`.
+ let span = and_span.to(self.look_ahead(1, |t| t.span));
+ let mut err = self.struct_span_err(span, "`mut` must precede `dyn`");
+ err.span_suggestion(
+ span,
+ "place `mut` before `dyn`",
+ "&mut dyn",
+ Applicability::MachineApplicable,
+ );
+ err.emit();
+
+ // Recovery
+ mutbl = Mutability::Mut;
+ let (dyn_tok, dyn_tok_sp) = (self.token.clone(), self.token_spacing);
+ self.bump();
+ self.bump_with((dyn_tok, dyn_tok_sp));
+ }
+ let ty = self.parse_ty_no_plus()?;
+ Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))
+ }
+
+ // Parses the `typeof(EXPR)`.
+ // To avoid ambiguity, the type is surrounded by parentheses.
+ fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
+ self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+ let expr = self.parse_anon_const_expr()?;
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+ Ok(TyKind::Typeof(expr))
+ }
+
+ /// Parses a function pointer type (`TyKind::BareFn`).
+ /// ```ignore (illustrative)
+ /// [unsafe] [extern "ABI"] fn (S) -> T
+ /// // ^~~~~^ ^~~~^ ^~^ ^
+ /// // | | | |
+ /// // | | | Return type
+ /// // Function Style ABI Parameter types
+ /// ```
+ /// We actually parse `FnHeader FnDecl`, but we error on `const` and `async` qualifiers.
+ fn parse_ty_bare_fn(
+ &mut self,
+ lo: Span,
+ params: Vec<GenericParam>,
+ recover_return_sign: RecoverReturnSign,
+ ) -> PResult<'a, TyKind> {
+ let inherited_vis = rustc_ast::Visibility {
+ span: rustc_span::DUMMY_SP,
+ kind: rustc_ast::VisibilityKind::Inherited,
+ tokens: None,
+ };
+ let span_start = self.token.span;
+ let ast::FnHeader { ext, unsafety, constness, asyncness } =
+ self.parse_fn_front_matter(&inherited_vis)?;
+ let decl = self.parse_fn_decl(|_| false, AllowPlus::No, recover_return_sign)?;
+ let whole_span = lo.to(self.prev_token.span);
+ if let ast::Const::Yes(span) = constness {
+ // If we ever start to allow `const fn()`, then update
+ // feature gating for `#![feature(const_extern_fn)]` to
+ // cover it.
+ self.error_fn_ptr_bad_qualifier(whole_span, span, "const");
+ }
+ if let ast::Async::Yes { span, .. } = asyncness {
+ self.error_fn_ptr_bad_qualifier(whole_span, span, "async");
+ }
+ let decl_span = span_start.to(self.token.span);
+ Ok(TyKind::BareFn(P(BareFnTy { ext, unsafety, generic_params: params, decl, decl_span })))
+ }
+
+ /// Emit an error for the given bad function pointer qualifier.
+ fn error_fn_ptr_bad_qualifier(&self, span: Span, qual_span: Span, qual: &str) {
+ self.struct_span_err(span, &format!("an `fn` pointer type cannot be `{}`", qual))
+ .span_label(qual_span, format!("`{}` because of this", qual))
+ .span_suggestion_short(
+ qual_span,
+ &format!("remove the `{}` qualifier", qual),
+ "",
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ /// Parses an `impl B0 + ... + Bn` type.
+ fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
+ // Always parse bounds greedily for better error recovery.
+ let bounds = self.parse_generic_bounds(None)?;
+ *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus);
+ Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
+ }
+
+ /// Is a `dyn B0 + ... + Bn` type allowed here?
+ fn is_explicit_dyn_type(&mut self) -> bool {
+ self.check_keyword(kw::Dyn)
+ && (!self.token.uninterpolated_span().rust_2015()
+ || self.look_ahead(1, |t| {
+ t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t)
+ }))
+ }
+
+ /// Parses a `dyn B0 + ... + Bn` type.
+ ///
+ /// Note that this does *not* parse bare trait objects.
+ fn parse_dyn_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
+ self.bump(); // `dyn`
+ // Always parse bounds greedily for better error recovery.
+ let bounds = self.parse_generic_bounds(None)?;
+ *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus);
+ Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn))
+ }
+
+ /// Parses a type starting with a path.
+ ///
+ /// This can be:
+ /// 1. a type macro, `mac!(...)`,
+ /// 2. a bare trait object, `B0 + ... + Bn`,
+ /// 3. or a path, `path::to::MyType`.
+ fn parse_path_start_ty(
+ &mut self,
+ lo: Span,
+ allow_plus: AllowPlus,
+ ty_generics: Option<&Generics>,
+ ) -> PResult<'a, TyKind> {
+ // Simple path
+ let path = self.parse_path_inner(PathStyle::Type, ty_generics)?;
+ if self.eat(&token::Not) {
+ // Macro invocation in type position
+ Ok(TyKind::MacCall(MacCall {
+ path,
+ args: self.parse_mac_args()?,
+ prior_type_ascription: self.last_type_ascription,
+ }))
+ } else if allow_plus == AllowPlus::Yes && self.check_plus() {
+ // `Trait1 + Trait2 + 'a`
+ self.parse_remaining_bounds_path(Vec::new(), path, lo, true)
+ } else {
+ // Just a type path.
+ Ok(TyKind::Path(None, path))
+ }
+ }
+
+ fn error_illegal_c_varadic_ty(&self, lo: Span) {
+ struct_span_err!(
+ self.sess.span_diagnostic,
+ lo.to(self.prev_token.span),
+ E0743,
+ "C-variadic type `...` may not be nested inside another type",
+ )
+ .emit();
+ }
+
+ pub(super) fn parse_generic_bounds(
+ &mut self,
+ colon_span: Option<Span>,
+ ) -> PResult<'a, GenericBounds> {
+ self.parse_generic_bounds_common(AllowPlus::Yes, colon_span)
+ }
+
+ /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
+ ///
+ /// See `parse_generic_bound` for the `BOUND` grammar.
+ fn parse_generic_bounds_common(
+ &mut self,
+ allow_plus: AllowPlus,
+ colon_span: Option<Span>,
+ ) -> PResult<'a, GenericBounds> {
+ let mut bounds = Vec::new();
+ let mut negative_bounds = Vec::new();
+
+ while self.can_begin_bound() || self.token.is_keyword(kw::Dyn) {
+ if self.token.is_keyword(kw::Dyn) {
+ // Account for `&dyn Trait + dyn Other`.
+ self.struct_span_err(self.token.span, "invalid `dyn` keyword")
+ .help("`dyn` is only needed at the start of a trait `+`-separated list")
+ .span_suggestion(
+ self.token.span,
+ "remove this keyword",
+ "",
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ self.bump();
+ }
+ match self.parse_generic_bound()? {
+ Ok(bound) => bounds.push(bound),
+ Err(neg_sp) => negative_bounds.push(neg_sp),
+ }
+ if allow_plus == AllowPlus::No || !self.eat_plus() {
+ break;
+ }
+ }
+
+ if !negative_bounds.is_empty() {
+ self.error_negative_bounds(colon_span, &bounds, negative_bounds);
+ }
+
+ Ok(bounds)
+ }
+
+ /// Can the current token begin a bound?
+ fn can_begin_bound(&mut self) -> bool {
+ // This needs to be synchronized with `TokenKind::can_begin_bound`.
+ self.check_path()
+ || self.check_lifetime()
+ || self.check(&token::Not) // Used for error reporting only.
+ || self.check(&token::Question)
+ || self.check(&token::Tilde)
+ || self.check_keyword(kw::For)
+ || self.check(&token::OpenDelim(Delimiter::Parenthesis))
+ }
+
+ fn error_negative_bounds(
+ &self,
+ colon_span: Option<Span>,
+ bounds: &[GenericBound],
+ negative_bounds: Vec<Span>,
+ ) {
+ let negative_bounds_len = negative_bounds.len();
+ let last_span = *negative_bounds.last().expect("no negative bounds, but still error?");
+ let mut err = self.struct_span_err(negative_bounds, "negative bounds are not supported");
+ err.span_label(last_span, "negative bounds are not supported");
+ if let Some(bound_list) = colon_span {
+ let bound_list = bound_list.to(self.prev_token.span);
+ let mut new_bound_list = String::new();
+ if !bounds.is_empty() {
+ let mut snippets = bounds.iter().map(|bound| self.span_to_snippet(bound.span()));
+ while let Some(Ok(snippet)) = snippets.next() {
+ new_bound_list.push_str(" + ");
+ new_bound_list.push_str(&snippet);
+ }
+ new_bound_list = new_bound_list.replacen(" +", ":", 1);
+ }
+ err.tool_only_span_suggestion(
+ bound_list,
+ &format!("remove the bound{}", pluralize!(negative_bounds_len)),
+ new_bound_list,
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ }
+
+ /// Parses a bound according to the grammar:
+ /// ```ebnf
+ /// BOUND = TY_BOUND | LT_BOUND
+ /// ```
+ fn parse_generic_bound(&mut self) -> PResult<'a, Result<GenericBound, Span>> {
+ let anchor_lo = self.prev_token.span;
+ let lo = self.token.span;
+ let has_parens = self.eat(&token::OpenDelim(Delimiter::Parenthesis));
+ let inner_lo = self.token.span;
+ let is_negative = self.eat(&token::Not);
+
+ let modifiers = self.parse_ty_bound_modifiers()?;
+ let bound = if self.token.is_lifetime() {
+ self.error_lt_bound_with_modifiers(modifiers);
+ self.parse_generic_lt_bound(lo, inner_lo, has_parens)?
+ } else {
+ self.parse_generic_ty_bound(lo, has_parens, modifiers)?
+ };
+
+ Ok(if is_negative { Err(anchor_lo.to(self.prev_token.span)) } else { Ok(bound) })
+ }
+
+ /// Parses a lifetime ("outlives") bound, e.g. `'a`, according to:
+ /// ```ebnf
+ /// LT_BOUND = LIFETIME
+ /// ```
+ fn parse_generic_lt_bound(
+ &mut self,
+ lo: Span,
+ inner_lo: Span,
+ has_parens: bool,
+ ) -> PResult<'a, GenericBound> {
+ let bound = GenericBound::Outlives(self.expect_lifetime());
+ if has_parens {
+ // FIXME(Centril): Consider not erroring here and accepting `('lt)` instead,
+ // possibly introducing `GenericBound::Paren(P<GenericBound>)`?
+ self.recover_paren_lifetime(lo, inner_lo)?;
+ }
+ Ok(bound)
+ }
+
+ /// Emits an error if any trait bound modifiers were present.
+ fn error_lt_bound_with_modifiers(&self, modifiers: BoundModifiers) {
+ if let Some(span) = modifiers.maybe_const {
+ self.struct_span_err(
+ span,
+ "`~const` may only modify trait bounds, not lifetime bounds",
+ )
+ .emit();
+ }
+
+ if let Some(span) = modifiers.maybe {
+ self.struct_span_err(span, "`?` may only modify trait bounds, not lifetime bounds")
+ .emit();
+ }
+ }
+
+ /// Recover on `('lifetime)` with `(` already eaten.
+ fn recover_paren_lifetime(&mut self, lo: Span, inner_lo: Span) -> PResult<'a, ()> {
+ let inner_span = inner_lo.to(self.prev_token.span);
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+ let mut err = self.struct_span_err(
+ lo.to(self.prev_token.span),
+ "parenthesized lifetime bounds are not supported",
+ );
+ if let Ok(snippet) = self.span_to_snippet(inner_span) {
+ err.span_suggestion_short(
+ lo.to(self.prev_token.span),
+ "remove the parentheses",
+ snippet,
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ Ok(())
+ }
+
+ /// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `~const Trait`.
+ ///
+ /// If no modifiers are present, this does not consume any tokens.
+ ///
+ /// ```ebnf
+ /// TY_BOUND_MODIFIERS = ["~const"] ["?"]
+ /// ```
+ fn parse_ty_bound_modifiers(&mut self) -> PResult<'a, BoundModifiers> {
+ let maybe_const = if self.eat(&token::Tilde) {
+ let tilde = self.prev_token.span;
+ self.expect_keyword(kw::Const)?;
+ let span = tilde.to(self.prev_token.span);
+ self.sess.gated_spans.gate(sym::const_trait_impl, span);
+ Some(span)
+ } else {
+ None
+ };
+
+ let maybe = if self.eat(&token::Question) { Some(self.prev_token.span) } else { None };
+
+ Ok(BoundModifiers { maybe, maybe_const })
+ }
+
+ /// Parses a type bound according to:
+ /// ```ebnf
+ /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
+ /// TY_BOUND_NOPAREN = [TY_BOUND_MODIFIERS] [for<LT_PARAM_DEFS>] SIMPLE_PATH
+ /// ```
+ ///
+ /// For example, this grammar accepts `~const ?for<'a: 'b> m::Trait<'a>`.
+ fn parse_generic_ty_bound(
+ &mut self,
+ lo: Span,
+ has_parens: bool,
+ modifiers: BoundModifiers,
+ ) -> PResult<'a, GenericBound> {
+ let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+ let path = self.parse_path(PathStyle::Type)?;
+ if has_parens {
+ if self.token.is_like_plus() {
+ // Someone has written something like `&dyn (Trait + Other)`. The correct code
+ // would be `&(dyn Trait + Other)`, but we don't have access to the appropriate
+ // span to suggest that. When written as `&dyn Trait + Other`, an appropriate
+ // suggestion is given.
+ let bounds = vec![];
+ self.parse_remaining_bounds(bounds, true)?;
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+ let sp = vec![lo, self.prev_token.span];
+ let sugg: Vec<_> = sp.iter().map(|sp| (*sp, String::new())).collect();
+ self.struct_span_err(sp, "incorrect braces around trait bounds")
+ .multipart_suggestion(
+ "remove the parentheses",
+ sugg,
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ } else {
+ self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+ }
+ }
+
+ let modifier = modifiers.to_trait_bound_modifier();
+ let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_token.span));
+ Ok(GenericBound::Trait(poly_trait, modifier))
+ }
+
+ /// Optionally parses `for<$generic_params>`.
+ pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
+ if self.eat_keyword(kw::For) {
+ self.expect_lt()?;
+ let params = self.parse_generic_params()?;
+ self.expect_gt()?;
+ // We rely on AST validation to rule out invalid cases: There must not be type
+ // parameters, and the lifetime parameters must not have bounds.
+ Ok(params)
+ } else {
+ Ok(Vec::new())
+ }
+ }
+
+ pub(super) fn check_lifetime(&mut self) -> bool {
+ self.expected_tokens.push(TokenType::Lifetime);
+ self.token.is_lifetime()
+ }
+
+ /// Parses a single lifetime `'a` or panics.
+ pub(super) fn expect_lifetime(&mut self) -> Lifetime {
+ if let Some(ident) = self.token.lifetime() {
+ self.bump();
+ Lifetime { ident, id: ast::DUMMY_NODE_ID }
+ } else {
+ self.span_bug(self.token.span, "not a lifetime")
+ }
+ }
+
+ pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
+ P(Ty { kind, span, id: ast::DUMMY_NODE_ID, tokens: None })
+ }
+}