diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/mod.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/mod.rs | 229 |
1 files changed, 53 insertions, 176 deletions
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index 48df8b59d55..968376678f3 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -12,7 +12,6 @@ pub mod token_type; mod ty; use std::assert_matches::debug_assert_matches; -use std::ops::Range; use std::{fmt, mem, slice}; use attr_wrapper::{AttrWrapper, UsePreAttrPos}; @@ -25,7 +24,9 @@ use rustc_ast::ptr::P; use rustc_ast::token::{ self, IdentIsRaw, InvisibleOrigin, MetaVarKind, NtExprKind, NtPatKind, Token, TokenKind, }; -use rustc_ast::tokenstream::{AttrsTarget, Spacing, TokenStream, TokenTree}; +use rustc_ast::tokenstream::{ + ParserRange, ParserReplacement, Spacing, TokenCursor, TokenStream, TokenTree, TokenTreeCursor, +}; use rustc_ast::util::case::Case; use rustc_ast::{ self as ast, AnonConst, AttrArgs, AttrId, ByRef, Const, CoroutineKind, DUMMY_NODE_ID, @@ -37,7 +38,7 @@ use rustc_data_structures::fx::FxHashMap; use rustc_errors::{Applicability, Diag, FatalError, MultiSpan, PResult}; use rustc_index::interval::IntervalSet; use rustc_session::parse::ParseSess; -use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym}; +use rustc_span::{Ident, Span, Symbol, kw, sym}; use thin_vec::ThinVec; use token_type::TokenTypeSet; pub use token_type::{ExpKeywordPair, ExpTokenPair, TokenType}; @@ -55,19 +56,64 @@ mod tests; mod tokenstream { mod tests; } -#[cfg(test)] -mod mut_visit { - mod tests; -} bitflags::bitflags! { + /// Restrictions applied while parsing. + /// + /// The parser maintains a bitset of restrictions it will honor while + /// parsing. This is essentially used as a way of tracking state of what + /// is being parsed and to change behavior based on that. #[derive(Clone, Copy, Debug)] struct Restrictions: u8 { + /// Restricts expressions for use in statement position. + /// + /// When expressions are used in various places, like statements or + /// match arms, this is used to stop parsing once certain tokens are + /// reached. + /// + /// For example, `if true {} & 1` with `STMT_EXPR` in effect is parsed + /// as two separate expression statements (`if` and a reference to 1). + /// Otherwise it is parsed as a bitwise AND where `if` is on the left + /// and 1 is on the right. const STMT_EXPR = 1 << 0; + /// Do not allow struct literals. + /// + /// There are several places in the grammar where we don't want to + /// allow struct literals because they can require lookahead, or + /// otherwise could be ambiguous or cause confusion. For example, + /// `if Foo {} {}` isn't clear if it is `Foo{}` struct literal, or + /// just `Foo` is the condition, followed by a consequent block, + /// followed by an empty block. + /// + /// See [RFC 92](https://rust-lang.github.io/rfcs/0092-struct-grammar.html). const NO_STRUCT_LITERAL = 1 << 1; + /// Used to provide better error messages for const generic arguments. + /// + /// An un-braced const generic argument is limited to a very small + /// subset of expressions. This is used to detect the situation where + /// an expression outside of that subset is used, and to suggest to + /// wrap the expression in braces. const CONST_EXPR = 1 << 2; + /// Allows `let` expressions. + /// + /// `let pattern = scrutinee` is parsed as an expression, but it is + /// only allowed in let chains (`if` and `while` conditions). + /// Otherwise it is not an expression (note that `let` in statement + /// positions is treated as a `StmtKind::Let` statement, which has a + /// slightly different grammar). const ALLOW_LET = 1 << 3; + /// Used to detect a missing `=>` in a match guard. + /// + /// This is used for error handling in a match guard to give a better + /// error message if the `=>` is missing. It is set when parsing the + /// guard expression. const IN_IF_GUARD = 1 << 4; + /// Used to detect the incorrect use of expressions in patterns. + /// + /// This is used for error handling while parsing a pattern. During + /// error recovery, this will be set to try to parse the pattern as an + /// expression, but halts parsing the expression when reaching certain + /// tokens like `=`. const IS_PAT = 1 << 5; } } @@ -187,57 +233,6 @@ struct ClosureSpans { body: Span, } -/// A token range within a `Parser`'s full token stream. -#[derive(Clone, Debug)] -struct ParserRange(Range<u32>); - -/// A token range within an individual AST node's (lazy) token stream, i.e. -/// relative to that node's first token. Distinct from `ParserRange` so the two -/// kinds of range can't be mixed up. -#[derive(Clone, Debug)] -struct NodeRange(Range<u32>); - -/// Indicates a range of tokens that should be replaced by an `AttrsTarget` -/// (replacement) or be replaced by nothing (deletion). This is used in two -/// places during token collection. -/// -/// 1. Replacement. During the parsing of an AST node that may have a -/// `#[derive]` attribute, when we parse a nested AST node that has `#[cfg]` -/// or `#[cfg_attr]`, we replace the entire inner AST node with -/// `FlatToken::AttrsTarget`. This lets us perform eager cfg-expansion on an -/// `AttrTokenStream`. -/// -/// 2. Deletion. We delete inner attributes from all collected token streams, -/// and instead track them through the `attrs` field on the AST node. This -/// lets us manipulate them similarly to outer attributes. When we create a -/// `TokenStream`, the inner attributes are inserted into the proper place -/// in the token stream. -/// -/// Each replacement starts off in `ParserReplacement` form but is converted to -/// `NodeReplacement` form when it is attached to a single AST node, via -/// `LazyAttrTokenStreamImpl`. -type ParserReplacement = (ParserRange, Option<AttrsTarget>); - -/// See the comment on `ParserReplacement`. -type NodeReplacement = (NodeRange, Option<AttrsTarget>); - -impl NodeRange { - // Converts a range within a parser's tokens to a range within a - // node's tokens beginning at `start_pos`. - // - // For example, imagine a parser with 50 tokens in its token stream, a - // function that spans `ParserRange(20..40)` and an inner attribute within - // that function that spans `ParserRange(30..35)`. We would find the inner - // attribute's range within the function's tokens by subtracting 20, which - // is the position of the function's start token. This gives - // `NodeRange(10..15)`. - fn new(ParserRange(parser_range): ParserRange, start_pos: u32) -> NodeRange { - assert!(!parser_range.is_empty()); - assert!(parser_range.start >= start_pos); - NodeRange((parser_range.start - start_pos)..(parser_range.end - start_pos)) - } -} - /// Controls how we capture tokens. Capturing can be expensive, /// so we try to avoid performing capturing in cases where /// we will never need an `AttrTokenStream`. @@ -260,104 +255,6 @@ struct CaptureState { seen_attrs: IntervalSet<AttrId>, } -#[derive(Clone, Debug)] -struct TokenTreeCursor { - stream: TokenStream, - /// Points to the current token tree in the stream. In `TokenCursor::curr`, - /// this can be any token tree. In `TokenCursor::stack`, this is always a - /// `TokenTree::Delimited`. - index: usize, -} - -impl TokenTreeCursor { - #[inline] - fn new(stream: TokenStream) -> Self { - TokenTreeCursor { stream, index: 0 } - } - - #[inline] - fn curr(&self) -> Option<&TokenTree> { - self.stream.get(self.index) - } - - fn look_ahead(&self, n: usize) -> Option<&TokenTree> { - self.stream.get(self.index + n) - } - - #[inline] - fn bump(&mut self) { - self.index += 1; - } -} - -/// A `TokenStream` cursor that produces `Token`s. It's a bit odd that -/// we (a) lex tokens into a nice tree structure (`TokenStream`), and then (b) -/// use this type to emit them as a linear sequence. But a linear sequence is -/// what the parser expects, for the most part. -#[derive(Clone, Debug)] -struct TokenCursor { - // Cursor for the current (innermost) token stream. The index within the - // cursor can point to any token tree in the stream (or one past the end). - // The delimiters for this token stream are found in `self.stack.last()`; - // if that is `None` we are in the outermost token stream which never has - // delimiters. - curr: TokenTreeCursor, - - // Token streams surrounding the current one. The index within each cursor - // always points to a `TokenTree::Delimited`. - stack: Vec<TokenTreeCursor>, -} - -impl TokenCursor { - fn next(&mut self) -> (Token, Spacing) { - self.inlined_next() - } - - /// This always-inlined version should only be used on hot code paths. - #[inline(always)] - fn inlined_next(&mut self) -> (Token, Spacing) { - loop { - // FIXME: we currently don't return `Delimiter::Invisible` 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.curr.curr() { - match tree { - &TokenTree::Token(token, spacing) => { - debug_assert!(!token.kind.is_delim()); - let res = (token, spacing); - self.curr.bump(); - return res; - } - &TokenTree::Delimited(sp, spacing, delim, ref tts) => { - let trees = TokenTreeCursor::new(tts.clone()); - self.stack.push(mem::replace(&mut self.curr, trees)); - if !delim.skip() { - return (Token::new(delim.as_open_token_kind(), sp.open), spacing.open); - } - // No open delimiter to return; continue on to the next iteration. - } - }; - } else if let Some(parent) = self.stack.pop() { - // We have exhausted this token stream. Move back to its parent token stream. - let Some(&TokenTree::Delimited(span, spacing, delim, _)) = parent.curr() else { - panic!("parent should be Delimited") - }; - self.curr = parent; - self.curr.bump(); // move past the `Delimited` - if !delim.skip() { - return (Token::new(delim.as_close_token_kind(), span.close), spacing.close); - } - // No close delimiter to return; continue on to the next iteration. - } else { - // We have exhausted the outermost token stream. The use of - // `Spacing::Alone` is arbitrary and immaterial, because the - // `Eof` token's spacing is never used. - return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone); - } - } - } -} - /// A sequence separator. #[derive(Debug)] struct SeqSep<'a> { @@ -1742,26 +1639,6 @@ impl<'a> Parser<'a> { } } -/// A helper struct used when building an `AttrTokenStream` from -/// a `LazyAttrTokenStream`. Both delimiter and non-delimited tokens -/// are stored as `FlatToken::Token`. A vector of `FlatToken`s -/// is then 'parsed' to build up an `AttrTokenStream` with nested -/// `AttrTokenTree::Delimited` tokens. -#[derive(Debug, Clone)] -enum FlatToken { - /// A token - this holds both delimiter (e.g. '{' and '}') - /// and non-delimiter tokens - Token((Token, Spacing)), - /// Holds the `AttrsTarget` for an AST node. The `AttrsTarget` is inserted - /// directly into the constructed `AttrTokenStream` as an - /// `AttrTokenTree::AttrsTarget`. - AttrsTarget(AttrsTarget), - /// A special 'empty' token that is ignored during the conversion - /// to an `AttrTokenStream`. This is used to simplify the - /// handling of replace ranges. - Empty, -} - // Metavar captures of various kinds. #[derive(Clone, Debug)] pub enum ParseNtResult { |