// option. This file may not be copied, modified, or distributed
// except according to those terms.
-use ast;
+use {ast, attr};
use ext::tt::macro_parser;
-use parse::{ParseSess, token};
+use feature_gate::{self, emit_feature_err, Features, GateIssue};
+use parse::{token, ParseSess};
use print::pprust;
use symbol::keywords;
-use syntax_pos::{DUMMY_SP, Span, BytePos};
+use syntax_pos::{BytePos, Span, DUMMY_SP};
use tokenstream;
+use std::cell::RefCell;
+use std::iter::Peekable;
use std::rc::Rc;
+/// 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, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
pub struct Delimited {
pub delim: token::DelimToken,
}
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 == DUMMY_SP {
DUMMY_SP
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 == DUMMY_SP {
DUMMY_SP
/// for token sequences.
#[derive(Clone, PartialEq, Eq, 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 `$(...)`
-/// are "first-class" token trees.
+/// are "first-class" token trees. Useful for parsing macros.
#[derive(Debug, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
pub enum TokenTree {
Token(Span, token::Token),
/// E.g. `$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 */),
+ 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 {
}
}
+ /// 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 {
}
}
+ /// 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 => {
/// Retrieve the `TokenTree`'s span.
pub fn span(&self) -> Span {
match *self {
- TokenTree::Token(sp, _) |
- TokenTree::MetaVar(sp, _) |
- TokenTree::MetaVarDecl(sp, _, _) |
- TokenTree::Delimited(sp, _) |
- TokenTree::Sequence(sp, _) => sp,
+ TokenTree::Token(sp, _)
+ | TokenTree::MetaVar(sp, _)
+ | TokenTree::MetaVarDecl(sp, _, _)
+ | TokenTree::Delimited(sp, _)
+ | TokenTree::Sequence(sp, _) => sp,
}
}
}
-pub fn parse(input: tokenstream::TokenStream, expect_matchers: bool, sess: &ParseSess)
- -> Vec<TokenTree> {
+/// 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 `$id:ident`. In this example, `expr` and
+/// `ident` are "matchers". They are not present in the body of a macro rule -- just in the
+/// pattern, so we pass a parameter to indicate whether to expect them or not.
+/// - `sess`: the parsing session. Any errors will be emitted to this session.
+/// - `features`, `attrs`: language feature flags and attributes so that we know whether to use
+/// unstable features or not.
+///
+/// # Returns
+///
+/// A collection of `self::TokenTree`. There may also be some errors emitted to `sess`.
+pub fn parse(
+ input: tokenstream::TokenStream,
+ expect_matchers: bool,
+ sess: &ParseSess,
+ features: &RefCell<Features>,
+ attrs: &[ast::Attribute],
+) -> Vec<TokenTree> {
+ // Will contain the final collection of `self::TokenTree`
let mut result = Vec::new();
- let mut trees = input.trees();
+
+ // For each token tree in `input`, parse the token into a `self::TokenTree`, consuming
+ // additional trees if need be.
+ let mut trees = input.trees().peekable();
while let Some(tree) = trees.next() {
- let tree = parse_tree(tree, &mut trees, expect_matchers, sess);
+ // Given the parsed tree, if there is a metavar and we are expecting matchers, actually
+ // parse out the matcher (i.e. in `$id:ident` this would parse the `:` and `ident`).
+ let tree = parse_tree(tree, &mut trees, expect_matchers, sess, features, attrs);
match tree {
TokenTree::MetaVar(start_sp, ident) if expect_matchers => {
let span = match trees.next() {
Some(kind) => {
let span = end_sp.with_lo(start_sp.lo());
result.push(TokenTree::MetaVarDecl(span, ident, kind));
- continue
+ continue;
}
_ => end_sp,
},
- tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+ tree => tree.as_ref()
+ .map(tokenstream::TokenTree::span)
+ .unwrap_or(span),
},
- tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(start_sp),
+ 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()));
+ 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
}
-fn parse_tree<I>(tree: tokenstream::TokenTree,
- trees: &mut I,
- expect_matchers: bool,
- sess: &ParseSess)
- -> TokenTree
- where I: Iterator<Item = tokenstream::TokenTree>,
+/// 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: &RefCell<Features>,
+ attrs: &[ast::Attribute],
+) -> 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, &msg);
}
- let sequence = parse(delimited.tts.into(), expect_matchers, sess);
- let (separator, op) = parse_sep_and_kleene_op(trees, span, sess);
+ // Parse the contents of the sequence itself
+ let sequence = parse(delimited.tts.into(), expect_matchers, sess, features, attrs);
+ // Get the Kleene operator and optional separator
+ let (separator, op) = parse_sep_and_kleene_op(trees, span, sess, features, attrs);
+ // Count the number of captured "names" (i.e. named metavars)
let name_captures = macro_parser::count_names(&sequence);
- TokenTree::Sequence(span, Rc::new(SequenceRepetition {
- tts: sequence,
- separator,
- op,
- num_captures: name_captures,
- }))
+ TokenTree::Sequence(
+ span,
+ Rc::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 invokation.
Some(tokenstream::TokenTree::Token(ident_span, ref token)) if token.is_ident() => {
let ident = token.ident().unwrap();
let span = ident_span.with_lo(span.lo());
if ident.name == keywords::Crate.name() {
- let ident = ast::Ident { name: keywords::DollarCrate.name(), ..ident };
+ let ident = ast::Ident {
+ name: keywords::DollarCrate.name(),
+ ..ident
+ };
TokenTree::Token(span, token::Ident(ident))
} 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));
+ 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),
- tokenstream::TokenTree::Delimited(span, delimited) => {
- TokenTree::Delimited(span, Rc::new(Delimited {
+
+ // `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,
+ Rc::new(Delimited {
delim: delimited.delim,
- tts: parse(delimited.tts.into(), expect_matchers, sess),
- }))
- }
+ tts: parse(delimited.tts.into(), expect_matchers, sess, features, attrs),
+ }),
+ ),
}
}
-fn parse_sep_and_kleene_op<I>(input: &mut I, span: Span, sess: &ParseSess)
- -> (Option<token::Token>, KleeneOp)
- where I: Iterator<Item = tokenstream::TokenTree>,
-{
- fn kleene_op(token: &token::Token) -> Option<KleeneOp> {
- match *token {
- token::BinOp(token::Star) => Some(KleeneOp::ZeroOrMore),
- token::BinOp(token::Plus) => Some(KleeneOp::OneOrMore),
- _ => None,
- }
+/// 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,
}
+}
- let span = match input.next() {
+/// Parse the next token tree of the input looking for a KleeneOp. Returns
+///
+/// - Ok(Ok(op)) 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, (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) => return (None, op),
- None => match input.next() {
- Some(tokenstream::TokenTree::Token(span, tok2)) => match kleene_op(&tok2) {
- Some(op) => return (Some(tok), op),
- None => span,
- },
- tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+ Some(op) => Ok(Ok(op)),
+ 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.
+fn parse_sep_and_kleene_op<I>(
+ input: &mut Peekable<I>,
+ span: Span,
+ sess: &ParseSess,
+ features: &RefCell<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 `+` or `*` KleeneOp
+ //
+ // `?` is ambiguous: it could be a separator or a Kleene::ZeroOrOne, 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 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)) => {
+ 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 a KleeneOp (this is the only valid option) :)
+ Ok(Ok(op)) if op == KleeneOp::ZeroOrOne => {
+ if !features.borrow().macro_at_most_once_rep
+ && !attr::contains_name(attrs, "allow_internal_unstable")
+ {
+ let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
+ emit_feature_err(
+ sess,
+ "macro_at_most_once_rep",
+ span,
+ GateIssue::Language,
+ explain,
+ );
+ }
+ return (Some(token::Question), op);
+ }
+ Ok(Ok(op)) => return (Some(token::Question), op),
+
+ // #2 is a random token (this is an error) :(
+ Ok(Err((_, span))) => span,
+
+ // #2 is not even a token at all :(
+ Err(span) => span,
+ }
+ } else {
+ if !features.borrow().macro_at_most_once_rep
+ && !attr::contains_name(attrs, "allow_internal_unstable")
+ {
+ let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
+ emit_feature_err(
+ sess,
+ "macro_at_most_once_rep",
+ span,
+ GateIssue::Language,
+ explain,
+ );
+ }
+
+ // #2 is a random tree and #1 is KleeneOp::ZeroOrOne
+ return (None, op);
}
+ }
+
+ // #1 is a separator followed by #2, a KleeneOp
+ Ok(Err((tok, span))) => match parse_kleene_op(input, span) {
+ // #2 is a KleeneOp :D
+ Ok(Ok(op)) if op == KleeneOp::ZeroOrOne => {
+ if !features.borrow().macro_at_most_once_rep
+ && !attr::contains_name(attrs, "allow_internal_unstable")
+ {
+ let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
+ emit_feature_err(
+ sess,
+ "macro_at_most_once_rep",
+ span,
+ GateIssue::Language,
+ explain,
+ );
+ }
+ return (Some(tok), op);
+ }
+ 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,
},
- tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+
+ // #1 is not a token
+ Err(span) => span,
};
- sess.span_diagnostic.span_err(span, "expected `*` or `+`");
+ if !features.borrow().macro_at_most_once_rep
+ && !attr::contains_name(attrs, "allow_internal_unstable")
+ {
+ sess.span_diagnostic
+ .span_err(span, "expected one of: `*`, `+`, or `?`");
+ } else {
+ sess.span_diagnostic.span_err(span, "expected `*` or `+`");
+ }
(None, KleeneOp::ZeroOrMore)
}
projects / rustc.git / blobdiff