| // Copyright 2017 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use ast::NodeId; |
| use early_buffered_lints::BufferedEarlyLintId; |
| use ext::tt::macro_parser; |
| use feature_gate::Features; |
| use parse::{token, ParseSess}; |
| use print::pprust; |
| use symbol::keywords; |
| use syntax_pos::{edition::Edition, BytePos, Span}; |
| use tokenstream::{self, DelimSpan}; |
| use ast; |
| |
| use rustc_data_structures::sync::Lrc; |
| use std::iter::Peekable; |
| |
| /// Contains the sub-token-trees of a "delimited" token tree, such as the contents of `(`. Note |
| /// that the delimiter itself might be `NoDelim`. |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug)] |
| pub struct Delimited { |
| pub delim: token::DelimToken, |
| pub tts: Vec<TokenTree>, |
| } |
| |
| impl Delimited { |
| /// Return the opening delimiter (possibly `NoDelim`). |
| pub fn open_token(&self) -> token::Token { |
| token::OpenDelim(self.delim) |
| } |
| |
| /// Return the closing delimiter (possibly `NoDelim`). |
| pub fn close_token(&self) -> token::Token { |
| token::CloseDelim(self.delim) |
| } |
| |
| /// Return a `self::TokenTree` with a `Span` corresponding to the opening delimiter. |
| pub fn open_tt(&self, span: Span) -> TokenTree { |
| let open_span = if span.is_dummy() { |
| span |
| } else { |
| span.with_lo(span.lo() + BytePos(self.delim.len() as u32)) |
| }; |
| TokenTree::Token(open_span, self.open_token()) |
| } |
| |
| /// Return a `self::TokenTree` with a `Span` corresponding to the closing delimiter. |
| pub fn close_tt(&self, span: Span) -> TokenTree { |
| let close_span = if span.is_dummy() { |
| span |
| } else { |
| span.with_lo(span.hi() - BytePos(self.delim.len() as u32)) |
| }; |
| TokenTree::Token(close_span, self.close_token()) |
| } |
| } |
| |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug)] |
| pub struct SequenceRepetition { |
| /// The sequence of token trees |
| pub tts: Vec<TokenTree>, |
| /// The optional separator |
| pub separator: Option<token::Token>, |
| /// Whether the sequence can be repeated zero (*), or one or more times (+) |
| pub op: KleeneOp, |
| /// The number of `Match`s that appear in the sequence (and subsequences) |
| pub num_captures: usize, |
| } |
| |
| /// A Kleene-style [repetition operator](http://en.wikipedia.org/wiki/Kleene_star) |
| /// for token sequences. |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)] |
| pub enum KleeneOp { |
| /// Kleene star (`*`) for zero or more repetitions |
| ZeroOrMore, |
| /// Kleene plus (`+`) for one or more repetitions |
| OneOrMore, |
| ZeroOrOne, |
| } |
| |
| /// Similar to `tokenstream::TokenTree`, except that `$i`, `$i:ident`, and `$(...)` |
| /// are "first-class" token trees. Useful for parsing macros. |
| #[derive(Debug, Clone, PartialEq, RustcEncodable, RustcDecodable)] |
| pub enum TokenTree { |
| Token(Span, token::Token), |
| Delimited(DelimSpan, Lrc<Delimited>), |
| /// A kleene-style repetition sequence |
| Sequence(DelimSpan, Lrc<SequenceRepetition>), |
| /// e.g., `$var` |
| MetaVar(Span, ast::Ident), |
| /// e.g., `$var:expr`. This is only used in the left hand side of MBE macros. |
| MetaVarDecl( |
| Span, |
| ast::Ident, /* name to bind */ |
| ast::Ident, /* kind of nonterminal */ |
| ), |
| } |
| |
| impl TokenTree { |
| /// Return the number of tokens in the tree. |
| pub fn len(&self) -> usize { |
| match *self { |
| TokenTree::Delimited(_, ref delimed) => match delimed.delim { |
| token::NoDelim => delimed.tts.len(), |
| _ => delimed.tts.len() + 2, |
| }, |
| TokenTree::Sequence(_, ref seq) => seq.tts.len(), |
| _ => 0, |
| } |
| } |
| |
| /// Returns true if the given token tree contains no other tokens. This is vacuously true for |
| /// single tokens or metavar/decls, but may be false for delimited trees or sequences. |
| pub fn is_empty(&self) -> bool { |
| match *self { |
| TokenTree::Delimited(_, ref delimed) => match delimed.delim { |
| token::NoDelim => delimed.tts.is_empty(), |
| _ => false, |
| }, |
| TokenTree::Sequence(_, ref seq) => seq.tts.is_empty(), |
| _ => true, |
| } |
| } |
| |
| /// Get the `index`-th sub-token-tree. This only makes sense for delimited trees and sequences. |
| pub fn get_tt(&self, index: usize) -> TokenTree { |
| match (self, index) { |
| (&TokenTree::Delimited(_, ref delimed), _) if delimed.delim == token::NoDelim => { |
| delimed.tts[index].clone() |
| } |
| (&TokenTree::Delimited(span, ref delimed), _) => { |
| if index == 0 { |
| return delimed.open_tt(span.open); |
| } |
| if index == delimed.tts.len() + 1 { |
| return delimed.close_tt(span.close); |
| } |
| delimed.tts[index - 1].clone() |
| } |
| (&TokenTree::Sequence(_, ref seq), _) => seq.tts[index].clone(), |
| _ => panic!("Cannot expand a token tree"), |
| } |
| } |
| |
| /// Retrieve the `TokenTree`'s span. |
| pub fn span(&self) -> Span { |
| match *self { |
| TokenTree::Token(sp, _) |
| | TokenTree::MetaVar(sp, _) |
| | TokenTree::MetaVarDecl(sp, _, _) => sp, |
| TokenTree::Delimited(sp, _) |
| | TokenTree::Sequence(sp, _) => sp.entire(), |
| } |
| } |
| } |
| |
| /// Takes a `tokenstream::TokenStream` and returns a `Vec<self::TokenTree>`. Specifically, this |
| /// takes a generic `TokenStream`, such as is used in the rest of the compiler, and returns a |
| /// collection of `TokenTree` for use in parsing a macro. |
| /// |
| /// # Parameters |
| /// |
| /// - `input`: a token stream to read from, the contents of which we are parsing. |
| /// - `expect_matchers`: `parse` can be used to parse either the "patterns" or the "body" of a |
| /// macro. Both take roughly the same form _except_ that in a pattern, metavars are declared with |
| /// their "matcher" type. For example `$var:expr` or `$id:ident`. In this example, `expr` and |
| /// `ident` are "matchers". They are not present in the body of a macro rule -- just in the |
| /// pattern, so we pass a parameter to indicate whether to expect them or not. |
| /// - `sess`: the parsing session. Any errors will be emitted to this session. |
| /// - `features`, `attrs`: language feature flags and attributes so that we know whether to use |
| /// unstable features or not. |
| /// - `edition`: which edition are we in. |
| /// - `macro_node_id`: the NodeId of the macro we are parsing. |
| /// |
| /// # Returns |
| /// |
| /// A collection of `self::TokenTree`. There may also be some errors emitted to `sess`. |
| pub fn parse( |
| input: tokenstream::TokenStream, |
| expect_matchers: bool, |
| sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| edition: Edition, |
| macro_node_id: NodeId, |
| ) -> Vec<TokenTree> { |
| // Will contain the final collection of `self::TokenTree` |
| let mut result = Vec::new(); |
| |
| // For each token tree in `input`, parse the token into a `self::TokenTree`, consuming |
| // additional trees if need be. |
| let mut trees = input.trees().peekable(); |
| while let Some(tree) = trees.next() { |
| // Given the parsed tree, if there is a metavar and we are expecting matchers, actually |
| // parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`). |
| let tree = parse_tree( |
| tree, |
| &mut trees, |
| expect_matchers, |
| sess, |
| features, |
| attrs, |
| edition, |
| macro_node_id, |
| ); |
| match tree { |
| TokenTree::MetaVar(start_sp, ident) if expect_matchers => { |
| let span = match trees.next() { |
| Some(tokenstream::TokenTree::Token(span, token::Colon)) => match trees.next() { |
| Some(tokenstream::TokenTree::Token(end_sp, ref tok)) => match tok.ident() { |
| Some((kind, _)) => { |
| let span = end_sp.with_lo(start_sp.lo()); |
| result.push(TokenTree::MetaVarDecl(span, ident, kind)); |
| continue; |
| } |
| _ => end_sp, |
| }, |
| tree => tree |
| .as_ref() |
| .map(tokenstream::TokenTree::span) |
| .unwrap_or(span), |
| }, |
| tree => tree |
| .as_ref() |
| .map(tokenstream::TokenTree::span) |
| .unwrap_or(start_sp), |
| }; |
| sess.missing_fragment_specifiers.borrow_mut().insert(span); |
| result.push(TokenTree::MetaVarDecl( |
| span, |
| ident, |
| keywords::Invalid.ident(), |
| )); |
| } |
| |
| // Not a metavar or no matchers allowed, so just return the tree |
| _ => result.push(tree), |
| } |
| } |
| result |
| } |
| |
| /// Takes a `tokenstream::TokenTree` and returns a `self::TokenTree`. Specifically, this takes a |
| /// generic `TokenTree`, such as is used in the rest of the compiler, and returns a `TokenTree` |
| /// for use in parsing a macro. |
| /// |
| /// Converting the given tree may involve reading more tokens. |
| /// |
| /// # Parameters |
| /// |
| /// - `tree`: the tree we wish to convert. |
| /// - `trees`: an iterator over trees. We may need to read more tokens from it in order to finish |
| /// converting `tree` |
| /// - `expect_matchers`: same as for `parse` (see above). |
| /// - `sess`: the parsing session. Any errors will be emitted to this session. |
| /// - `features`, `attrs`: language feature flags and attributes so that we know whether to use |
| /// unstable features or not. |
| fn parse_tree<I>( |
| tree: tokenstream::TokenTree, |
| trees: &mut Peekable<I>, |
| expect_matchers: bool, |
| sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| edition: Edition, |
| macro_node_id: NodeId, |
| ) -> TokenTree |
| where |
| I: Iterator<Item = tokenstream::TokenTree>, |
| { |
| // Depending on what `tree` is, we could be parsing different parts of a macro |
| match tree { |
| // `tree` is a `$` token. Look at the next token in `trees` |
| tokenstream::TokenTree::Token(span, token::Dollar) => match trees.next() { |
| // `tree` is followed by a delimited set of token trees. This indicates the beginning |
| // of a repetition sequence in the macro (e.g., `$(pat)*`). |
| Some(tokenstream::TokenTree::Delimited(span, delimited)) => { |
| // Must have `(` not `{` or `[` |
| if delimited.delim != token::Paren { |
| let tok = pprust::token_to_string(&token::OpenDelim(delimited.delim)); |
| let msg = format!("expected `(`, found `{}`", tok); |
| sess.span_diagnostic.span_err(span.entire(), &msg); |
| } |
| // Parse the contents of the sequence itself |
| let sequence = parse( |
| delimited.tts.into(), |
| expect_matchers, |
| sess, |
| features, |
| attrs, |
| edition, |
| macro_node_id, |
| ); |
| // Get the Kleene operator and optional separator |
| let (separator, op) = |
| parse_sep_and_kleene_op( |
| trees, |
| span.entire(), |
| sess, |
| features, |
| attrs, |
| edition, |
| macro_node_id, |
| ); |
| // Count the number of captured "names" (i.e., named metavars) |
| let name_captures = macro_parser::count_names(&sequence); |
| TokenTree::Sequence( |
| span, |
| Lrc::new(SequenceRepetition { |
| tts: sequence, |
| separator, |
| op, |
| num_captures: name_captures, |
| }), |
| ) |
| } |
| |
| // `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate` special |
| // metavariable that names the crate of the invocation. |
| Some(tokenstream::TokenTree::Token(ident_span, ref token)) if token.is_ident() => { |
| let (ident, is_raw) = token.ident().unwrap(); |
| let span = ident_span.with_lo(span.lo()); |
| if ident.name == keywords::Crate.name() && !is_raw { |
| let ident = ast::Ident::new(keywords::DollarCrate.name(), ident.span); |
| TokenTree::Token(span, token::Ident(ident, is_raw)) |
| } else { |
| TokenTree::MetaVar(span, ident) |
| } |
| } |
| |
| // `tree` is followed by a random token. This is an error. |
| Some(tokenstream::TokenTree::Token(span, tok)) => { |
| let msg = format!( |
| "expected identifier, found `{}`", |
| pprust::token_to_string(&tok) |
| ); |
| sess.span_diagnostic.span_err(span, &msg); |
| TokenTree::MetaVar(span, keywords::Invalid.ident()) |
| } |
| |
| // There are no more tokens. Just return the `$` we already have. |
| None => TokenTree::Token(span, token::Dollar), |
| }, |
| |
| // `tree` is an arbitrary token. Keep it. |
| tokenstream::TokenTree::Token(span, tok) => TokenTree::Token(span, tok), |
| |
| // `tree` is the beginning of a delimited set of tokens (e.g., `(` or `{`). We need to |
| // descend into the delimited set and further parse it. |
| tokenstream::TokenTree::Delimited(span, delimited) => TokenTree::Delimited( |
| span, |
| Lrc::new(Delimited { |
| delim: delimited.delim, |
| tts: parse( |
| delimited.tts.into(), |
| expect_matchers, |
| sess, |
| features, |
| attrs, |
| edition, |
| macro_node_id, |
| ), |
| }), |
| ), |
| } |
| } |
| |
| /// Takes a token and returns `Some(KleeneOp)` if the token is `+` `*` or `?`. Otherwise, return |
| /// `None`. |
| fn kleene_op(token: &token::Token) -> Option<KleeneOp> { |
| match *token { |
| token::BinOp(token::Star) => Some(KleeneOp::ZeroOrMore), |
| token::BinOp(token::Plus) => Some(KleeneOp::OneOrMore), |
| token::Question => Some(KleeneOp::ZeroOrOne), |
| _ => None, |
| } |
| } |
| |
| /// Parse the next token tree of the input looking for a KleeneOp. Returns |
| /// |
| /// - Ok(Ok((op, span))) if the next token tree is a KleeneOp |
| /// - Ok(Err(tok, span)) if the next token tree is a token but not a KleeneOp |
| /// - Err(span) if the next token tree is not a token |
| fn parse_kleene_op<I>( |
| input: &mut I, |
| span: Span, |
| ) -> Result<Result<(KleeneOp, Span), (token::Token, Span)>, Span> |
| where |
| I: Iterator<Item = tokenstream::TokenTree>, |
| { |
| match input.next() { |
| Some(tokenstream::TokenTree::Token(span, tok)) => match kleene_op(&tok) { |
| Some(op) => Ok(Ok((op, span))), |
| None => Ok(Err((tok, span))), |
| }, |
| tree => Err(tree |
| .as_ref() |
| .map(tokenstream::TokenTree::span) |
| .unwrap_or(span)), |
| } |
| } |
| |
| /// Attempt to parse a single Kleene star, possibly with a separator. |
| /// |
| /// For example, in a pattern such as `$(a),*`, `a` is the pattern to be repeated, `,` is the |
| /// separator, and `*` is the Kleene operator. This function is specifically concerned with parsing |
| /// the last two tokens of such a pattern: namely, the optional separator and the Kleene operator |
| /// itself. Note that here we are parsing the _macro_ itself, rather than trying to match some |
| /// stream of tokens in an invocation of a macro. |
| /// |
| /// This function will take some input iterator `input` corresponding to `span` and a parsing |
| /// session `sess`. If the next one (or possibly two) tokens in `input` correspond to a Kleene |
| /// operator and separator, then a tuple with `(separator, KleeneOp)` is returned. Otherwise, an |
| /// error with the appropriate span is emitted to `sess` and a dummy value is returned. |
| /// |
| /// NOTE: In 2015 edition, * and + are the only Kleene operators and `?` is a separator. In 2018, |
| /// `?` is a Kleene op and not a separator. |
| fn parse_sep_and_kleene_op<I>( |
| input: &mut Peekable<I>, |
| span: Span, |
| sess: &ParseSess, |
| features: &Features, |
| attrs: &[ast::Attribute], |
| edition: Edition, |
| macro_node_id: NodeId, |
| ) -> (Option<token::Token>, KleeneOp) |
| where |
| I: Iterator<Item = tokenstream::TokenTree>, |
| { |
| match edition { |
| Edition::Edition2015 => parse_sep_and_kleene_op_2015( |
| input, |
| span, |
| sess, |
| features, |
| attrs, |
| macro_node_id, |
| ), |
| Edition::Edition2018 => parse_sep_and_kleene_op_2018(input, span, sess, features, attrs), |
| } |
| } |
| |
| // `?` is a separator (with a migration warning) and never a KleeneOp. |
| fn parse_sep_and_kleene_op_2015<I>( |
| input: &mut Peekable<I>, |
| span: Span, |
| sess: &ParseSess, |
| _features: &Features, |
| _attrs: &[ast::Attribute], |
| macro_node_id: NodeId, |
| ) -> (Option<token::Token>, KleeneOp) |
| where |
| I: Iterator<Item = tokenstream::TokenTree>, |
| { |
| // We basically look at two token trees here, denoted as #1 and #2 below |
| let span = match parse_kleene_op(input, span) { |
| // #1 is a `+` or `*` KleeneOp |
| // |
| // `?` is ambiguous: it could be a separator (warning) or a Kleene::ZeroOrOne (error), so |
| // we need to look ahead one more token to be sure. |
| Ok(Ok((op, _))) if op != KleeneOp::ZeroOrOne => return (None, op), |
| |
| // #1 is `?` token, but it could be a Kleene::ZeroOrOne (error in 2015) without a separator |
| // or it could be a `?` separator followed by any Kleene operator. We need to look ahead 1 |
| // token to find out which. |
| Ok(Ok((op, op1_span))) => { |
| assert_eq!(op, KleeneOp::ZeroOrOne); |
| |
| // Lookahead at #2. If it is a KleenOp, then #1 is a separator. |
| let is_1_sep = if let Some(&tokenstream::TokenTree::Token(_, ref tok2)) = input.peek() { |
| kleene_op(tok2).is_some() |
| } else { |
| false |
| }; |
| |
| if is_1_sep { |
| // #1 is a separator and #2 should be a KleepeOp. |
| // (N.B. We need to advance the input iterator.) |
| match parse_kleene_op(input, span) { |
| // #2 is `?`, which is not allowed as a Kleene op in 2015 edition. |
| Ok(Ok((op, op2_span))) if op == KleeneOp::ZeroOrOne => { |
| sess.span_diagnostic |
| .struct_span_err(op2_span, "expected `*` or `+`") |
| .note("`?` is not a macro repetition operator") |
| .emit(); |
| |
| // Return a dummy |
| return (None, KleeneOp::ZeroOrMore); |
| } |
| |
| // #2 is a Kleene op, which is the only valid option |
| Ok(Ok((op, _))) => { |
| // Warn that `?` as a separator will be deprecated |
| sess.buffer_lint( |
| BufferedEarlyLintId::QuestionMarkMacroSep, |
| op1_span, |
| macro_node_id, |
| "using `?` as a separator is deprecated and will be \ |
| a hard error in an upcoming edition", |
| ); |
| |
| return (Some(token::Question), op); |
| } |
| |
| // #2 is a random token (this is an error) :( |
| Ok(Err((_, _))) => op1_span, |
| |
| // #2 is not even a token at all :( |
| Err(_) => op1_span, |
| } |
| } else { |
| // `?` is not allowed as a Kleene op in 2015 |
| sess.span_diagnostic |
| .struct_span_err(op1_span, "expected `*` or `+`") |
| .note("`?` is not a macro repetition operator") |
| .emit(); |
| |
| // Return a dummy |
| return (None, KleeneOp::ZeroOrMore); |
| } |
| } |
| |
| // #1 is a separator followed by #2, a KleeneOp |
| Ok(Err((tok, span))) => match parse_kleene_op(input, span) { |
| // #2 is a `?`, which is not allowed as a Kleene op in 2015 edition. |
| Ok(Ok((op, op2_span))) if op == KleeneOp::ZeroOrOne => { |
| sess.span_diagnostic |
| .struct_span_err(op2_span, "expected `*` or `+`") |
| .note("`?` is not a macro repetition operator") |
| .emit(); |
| |
| // Return a dummy |
| return (None, KleeneOp::ZeroOrMore); |
| } |
| |
| // #2 is a KleeneOp :D |
| Ok(Ok((op, _))) => return (Some(tok), op), |
| |
| // #2 is a random token :( |
| Ok(Err((_, span))) => span, |
| |
| // #2 is not a token at all :( |
| Err(span) => span, |
| }, |
| |
| // #1 is not a token |
| Err(span) => span, |
| }; |
| |
| sess.span_diagnostic.span_err(span, "expected `*` or `+`"); |
| |
| // Return a dummy |
| (None, KleeneOp::ZeroOrMore) |
| } |
| |
| // `?` is a Kleene op, not a separator |
| fn parse_sep_and_kleene_op_2018<I>( |
| input: &mut Peekable<I>, |
| span: Span, |
| sess: &ParseSess, |
| _features: &Features, |
| _attrs: &[ast::Attribute], |
| ) -> (Option<token::Token>, KleeneOp) |
| where |
| I: Iterator<Item = tokenstream::TokenTree>, |
| { |
| // We basically look at two token trees here, denoted as #1 and #2 below |
| let span = match parse_kleene_op(input, span) { |
| // #1 is a `?` (needs feature gate) |
| Ok(Ok((op, _op1_span))) if op == KleeneOp::ZeroOrOne => { |
| return (None, op); |
| } |
| |
| // #1 is a `+` or `*` KleeneOp |
| Ok(Ok((op, _))) => return (None, op), |
| |
| // #1 is a separator followed by #2, a KleeneOp |
| Ok(Err((tok, span))) => match parse_kleene_op(input, span) { |
| // #2 is the `?` Kleene op, which does not take a separator (error) |
| Ok(Ok((op, _op2_span))) if op == KleeneOp::ZeroOrOne => { |
| // Error! |
| sess.span_diagnostic.span_err( |
| span, |
| "the `?` macro repetition operator does not take a separator", |
| ); |
| |
| // Return a dummy |
| return (None, KleeneOp::ZeroOrMore); |
| } |
| |
| // #2 is a KleeneOp :D |
| Ok(Ok((op, _))) => return (Some(tok), op), |
| |
| // #2 is a random token :( |
| Ok(Err((_, span))) => span, |
| |
| // #2 is not a token at all :( |
| Err(span) => span, |
| }, |
| |
| // #1 is not a token |
| Err(span) => span, |
| }; |
| |
| // If we ever get to this point, we have experienced an "unexpected token" error |
| sess.span_diagnostic |
| .span_err(span, "expected one of: `*`, `+`, or `?`"); |
| |
| // Return a dummy |
| (None, KleeneOp::ZeroOrMore) |
| } |