395 lines
19 KiB
Rust
395 lines
19 KiB
Rust
use rustc_ast::token::{self, Delimiter, IdentIsRaw, NonterminalKind, Token};
|
|
use rustc_ast::tokenstream::TokenStreamIter;
|
|
use rustc_ast::{NodeId, tokenstream};
|
|
use rustc_ast_pretty::pprust;
|
|
use rustc_feature::Features;
|
|
use rustc_session::Session;
|
|
use rustc_session::parse::feature_err;
|
|
use rustc_span::edition::Edition;
|
|
use rustc_span::{Ident, Span, kw, sym};
|
|
|
|
use crate::errors;
|
|
use crate::mbe::macro_parser::count_metavar_decls;
|
|
use crate::mbe::{Delimited, KleeneOp, KleeneToken, MetaVarExpr, SequenceRepetition, TokenTree};
|
|
|
|
pub(crate) const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \
|
|
`ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, \
|
|
`meta`, `tt`, `item` and `vis`, along with `expr_2021` and `pat_param` for edition compatibility";
|
|
|
|
/// 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.
|
|
/// - `parsing_patterns`: `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.
|
|
/// - Metavariable expressions are only valid in the "body", not the "pattern".
|
|
/// - `sess`: the parsing session. Any errors will be emitted to this session.
|
|
/// - `node_id`: the NodeId of the macro we are parsing.
|
|
/// - `features`: language features so we can do feature gating.
|
|
///
|
|
/// # Returns
|
|
///
|
|
/// A collection of `self::TokenTree`. There may also be some errors emitted to `sess`.
|
|
pub(super) fn parse(
|
|
input: &tokenstream::TokenStream,
|
|
parsing_patterns: bool,
|
|
sess: &Session,
|
|
node_id: NodeId,
|
|
features: &Features,
|
|
edition: Edition,
|
|
) -> 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 iter = input.iter();
|
|
while let Some(tree) = iter.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 iter, parsing_patterns, sess, node_id, features, edition);
|
|
match tree {
|
|
TokenTree::MetaVar(start_sp, ident) if parsing_patterns => {
|
|
// Not consuming the next token immediately, as it may not be a colon
|
|
let span = match iter.peek() {
|
|
Some(&tokenstream::TokenTree::Token(
|
|
Token { kind: token::Colon, span: colon_span },
|
|
_,
|
|
)) => {
|
|
// Consume the colon first
|
|
iter.next();
|
|
|
|
// It's ok to consume the next tree no matter how,
|
|
// since if it's not a token then it will be an invalid declaration.
|
|
match iter.next() {
|
|
Some(tokenstream::TokenTree::Token(token, _)) => match token.ident() {
|
|
Some((fragment, _)) => {
|
|
let span = token.span.with_lo(start_sp.lo());
|
|
let edition = || {
|
|
// FIXME(#85708) - once we properly decode a foreign
|
|
// crate's `SyntaxContext::root`, then we can replace
|
|
// this with just `span.edition()`. A
|
|
// `SyntaxContext::root()` from the current crate will
|
|
// have the edition of the current crate, and a
|
|
// `SyntaxContext::root()` from a foreign crate will
|
|
// have the edition of that crate (which we manually
|
|
// retrieve via the `edition` parameter).
|
|
if !span.from_expansion() {
|
|
edition
|
|
} else {
|
|
span.edition()
|
|
}
|
|
};
|
|
let kind = NonterminalKind::from_symbol(fragment.name, edition)
|
|
.unwrap_or_else(|| {
|
|
sess.dcx().emit_err(errors::InvalidFragmentSpecifier {
|
|
span,
|
|
fragment,
|
|
help: VALID_FRAGMENT_NAMES_MSG.into(),
|
|
});
|
|
NonterminalKind::Ident
|
|
});
|
|
result.push(TokenTree::MetaVarDecl(span, ident, Some(kind)));
|
|
continue;
|
|
}
|
|
_ => token.span,
|
|
},
|
|
// Invalid, return a nice source location
|
|
_ => colon_span.with_lo(start_sp.lo()),
|
|
}
|
|
}
|
|
// Whether it's none or some other tree, it doesn't belong to
|
|
// the current meta variable, returning the original span.
|
|
_ => start_sp,
|
|
};
|
|
|
|
result.push(TokenTree::MetaVarDecl(span, ident, None));
|
|
}
|
|
|
|
// Not a metavar or no matchers allowed, so just return the tree
|
|
_ => result.push(tree),
|
|
}
|
|
}
|
|
result
|
|
}
|
|
|
|
/// Asks for the `macro_metavar_expr` feature if it is not enabled
|
|
fn maybe_emit_macro_metavar_expr_feature(features: &Features, sess: &Session, span: Span) {
|
|
if !features.macro_metavar_expr() {
|
|
let msg = "meta-variable expressions are unstable";
|
|
feature_err(sess, sym::macro_metavar_expr, span, msg).emit();
|
|
}
|
|
}
|
|
|
|
fn maybe_emit_macro_metavar_expr_concat_feature(features: &Features, sess: &Session, span: Span) {
|
|
if !features.macro_metavar_expr_concat() {
|
|
let msg = "the `concat` meta-variable expression is unstable";
|
|
feature_err(sess, sym::macro_metavar_expr_concat, span, msg).emit();
|
|
}
|
|
}
|
|
|
|
/// 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.
|
|
/// - `outer_iter`: an iterator over trees. We may need to read more tokens from it in order to finish
|
|
/// converting `tree`
|
|
/// - `parsing_patterns`: same as [parse].
|
|
/// - `sess`: the parsing session. Any errors will be emitted to this session.
|
|
/// - `features`: language features so we can do feature gating.
|
|
fn parse_tree<'a>(
|
|
tree: &'a tokenstream::TokenTree,
|
|
outer_iter: &mut TokenStreamIter<'a>,
|
|
parsing_patterns: bool,
|
|
sess: &Session,
|
|
node_id: NodeId,
|
|
features: &Features,
|
|
edition: Edition,
|
|
) -> 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(Token { kind: token::Dollar, span: dollar_span }, _) => {
|
|
// FIXME: Handle `Invisible`-delimited groups in a more systematic way
|
|
// during parsing.
|
|
let mut next = outer_iter.next();
|
|
let mut iter_storage;
|
|
let mut iter: &mut TokenStreamIter<'_> = match next {
|
|
Some(tokenstream::TokenTree::Delimited(.., delim, tts)) if delim.skip() => {
|
|
iter_storage = tts.iter();
|
|
next = iter_storage.next();
|
|
&mut iter_storage
|
|
}
|
|
_ => outer_iter,
|
|
};
|
|
|
|
match next {
|
|
// `tree` is followed by a delimited set of token trees.
|
|
Some(&tokenstream::TokenTree::Delimited(delim_span, _, delim, ref tts)) => {
|
|
if parsing_patterns {
|
|
if delim != Delimiter::Parenthesis {
|
|
span_dollar_dollar_or_metavar_in_the_lhs_err(
|
|
sess,
|
|
&Token { kind: token::OpenDelim(delim), span: delim_span.entire() },
|
|
);
|
|
}
|
|
} else {
|
|
match delim {
|
|
Delimiter::Brace => {
|
|
// The delimiter is `{`. This indicates the beginning
|
|
// of a meta-variable expression (e.g. `${count(ident)}`).
|
|
// Try to parse the meta-variable expression.
|
|
match MetaVarExpr::parse(tts, delim_span.entire(), &sess.psess) {
|
|
Err(err) => {
|
|
err.emit();
|
|
// Returns early the same read `$` to avoid spanning
|
|
// unrelated diagnostics that could be performed afterwards
|
|
return TokenTree::token(token::Dollar, dollar_span);
|
|
}
|
|
Ok(elem) => {
|
|
if let MetaVarExpr::Concat(_) = elem {
|
|
maybe_emit_macro_metavar_expr_concat_feature(
|
|
features,
|
|
sess,
|
|
delim_span.entire(),
|
|
);
|
|
} else {
|
|
maybe_emit_macro_metavar_expr_feature(
|
|
features,
|
|
sess,
|
|
delim_span.entire(),
|
|
);
|
|
}
|
|
return TokenTree::MetaVarExpr(delim_span, elem);
|
|
}
|
|
}
|
|
}
|
|
Delimiter::Parenthesis => {}
|
|
_ => {
|
|
let token = pprust::token_kind_to_string(&token::OpenDelim(delim));
|
|
sess.dcx().emit_err(errors::ExpectedParenOrBrace {
|
|
span: delim_span.entire(),
|
|
token,
|
|
});
|
|
}
|
|
}
|
|
}
|
|
// If we didn't find a metavar expression above, then we must have a
|
|
// repetition sequence in the macro (e.g. `$(pat)*`). Parse the
|
|
// contents of the sequence itself
|
|
let sequence = parse(tts, parsing_patterns, sess, node_id, features, edition);
|
|
// Get the Kleene operator and optional separator
|
|
let (separator, kleene) =
|
|
parse_sep_and_kleene_op(&mut iter, delim_span.entire(), sess);
|
|
// Count the number of captured "names" (i.e., named metavars)
|
|
let num_captures =
|
|
if parsing_patterns { count_metavar_decls(&sequence) } else { 0 };
|
|
TokenTree::Sequence(
|
|
delim_span,
|
|
SequenceRepetition { tts: sequence, separator, kleene, num_captures },
|
|
)
|
|
}
|
|
|
|
// `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate`
|
|
// special metavariable that names the crate of the invocation.
|
|
Some(tokenstream::TokenTree::Token(token, _)) if token.is_ident() => {
|
|
let (ident, is_raw) = token.ident().unwrap();
|
|
let span = ident.span.with_lo(dollar_span.lo());
|
|
if ident.name == kw::Crate && matches!(is_raw, IdentIsRaw::No) {
|
|
TokenTree::token(token::Ident(kw::DollarCrate, is_raw), span)
|
|
} else {
|
|
TokenTree::MetaVar(span, ident)
|
|
}
|
|
}
|
|
|
|
// `tree` is followed by another `$`. This is an escaped `$`.
|
|
Some(&tokenstream::TokenTree::Token(
|
|
Token { kind: token::Dollar, span: dollar_span2 },
|
|
_,
|
|
)) => {
|
|
if parsing_patterns {
|
|
span_dollar_dollar_or_metavar_in_the_lhs_err(
|
|
sess,
|
|
&Token { kind: token::Dollar, span: dollar_span2 },
|
|
);
|
|
} else {
|
|
maybe_emit_macro_metavar_expr_feature(features, sess, dollar_span2);
|
|
}
|
|
TokenTree::token(token::Dollar, dollar_span2)
|
|
}
|
|
|
|
// `tree` is followed by some other token. This is an error.
|
|
Some(tokenstream::TokenTree::Token(token, _)) => {
|
|
let msg =
|
|
format!("expected identifier, found `{}`", pprust::token_to_string(token),);
|
|
sess.dcx().span_err(token.span, msg);
|
|
TokenTree::MetaVar(token.span, Ident::empty())
|
|
}
|
|
|
|
// There are no more tokens. Just return the `$` we already have.
|
|
None => TokenTree::token(token::Dollar, dollar_span),
|
|
}
|
|
}
|
|
|
|
// `tree` is an arbitrary token. Keep it.
|
|
tokenstream::TokenTree::Token(token, _) => TokenTree::Token(token.clone()),
|
|
|
|
// `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, spacing, delim, ref tts) => TokenTree::Delimited(
|
|
span,
|
|
spacing,
|
|
Delimited {
|
|
delim,
|
|
tts: parse(tts, parsing_patterns, sess, node_id, features, edition),
|
|
},
|
|
),
|
|
}
|
|
}
|
|
|
|
/// Takes a token and returns `Some(KleeneOp)` if the token is `+` `*` or `?`. Otherwise, return
|
|
/// `None`.
|
|
fn kleene_op(token: &Token) -> Option<KleeneOp> {
|
|
match token.kind {
|
|
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(
|
|
iter: &mut TokenStreamIter<'_>,
|
|
span: Span,
|
|
) -> Result<Result<(KleeneOp, Span), Token>, Span> {
|
|
match iter.next() {
|
|
Some(tokenstream::TokenTree::Token(token, _)) => match kleene_op(token) {
|
|
Some(op) => Ok(Ok((op, token.span))),
|
|
None => Ok(Err(token.clone())),
|
|
},
|
|
tree => Err(tree.map_or(span, tokenstream::TokenTree::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 `iter` corresponding to `span` and a parsing
|
|
/// session `sess`. If the next one (or possibly two) tokens in `iter` 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(
|
|
iter: &mut TokenStreamIter<'_>,
|
|
span: Span,
|
|
sess: &Session,
|
|
) -> (Option<Token>, KleeneToken) {
|
|
// We basically look at two token trees here, denoted as #1 and #2 below
|
|
let span = match parse_kleene_op(iter, span) {
|
|
// #1 is a `?`, `+`, or `*` KleeneOp
|
|
Ok(Ok((op, span))) => return (None, KleeneToken::new(op, span)),
|
|
|
|
// #1 is a separator followed by #2, a KleeneOp
|
|
Ok(Err(token)) => match parse_kleene_op(iter, token.span) {
|
|
// #2 is the `?` Kleene op, which does not take a separator (error)
|
|
Ok(Ok((KleeneOp::ZeroOrOne, span))) => {
|
|
// Error!
|
|
sess.dcx().span_err(
|
|
token.span,
|
|
"the `?` macro repetition operator does not take a separator",
|
|
);
|
|
|
|
// Return a dummy
|
|
return (None, KleeneToken::new(KleeneOp::ZeroOrMore, span));
|
|
}
|
|
|
|
// #2 is a KleeneOp :D
|
|
Ok(Ok((op, span))) => return (Some(token), KleeneToken::new(op, span)),
|
|
|
|
// #2 is a random token or not a token at all :(
|
|
Ok(Err(Token { span, .. })) | 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.dcx().span_err(span, "expected one of: `*`, `+`, or `?`");
|
|
|
|
// Return a dummy
|
|
(None, KleeneToken::new(KleeneOp::ZeroOrMore, span))
|
|
}
|
|
|
|
// `$$` or a meta-variable is the lhs of a macro but shouldn't.
|
|
//
|
|
// For example, `macro_rules! foo { ( ${len()} ) => {} }`
|
|
fn span_dollar_dollar_or_metavar_in_the_lhs_err(sess: &Session, token: &Token) {
|
|
sess.dcx()
|
|
.span_err(token.span, format!("unexpected token: {}", pprust::token_to_string(token)));
|
|
sess.dcx().span_note(
|
|
token.span,
|
|
"`$$` and meta-variable expressions are not allowed inside macro parameter definitions",
|
|
);
|
|
}
|