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Diffstat (limited to 'src/libsyntax_expand/mbe/quoted.rs')
| -rw-r--r-- | src/libsyntax_expand/mbe/quoted.rs | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/src/libsyntax_expand/mbe/quoted.rs b/src/libsyntax_expand/mbe/quoted.rs new file mode 100644 index 00000000000..cedd59233ad --- /dev/null +++ b/src/libsyntax_expand/mbe/quoted.rs @@ -0,0 +1,264 @@ +use crate::mbe::macro_parser; +use crate::mbe::{TokenTree, KleeneOp, KleeneToken, SequenceRepetition, Delimited}; + +use syntax::ast; +use syntax::parse::token::{self, Token}; +use syntax::print::pprust; +use syntax::sess::ParseSess; +use syntax::symbol::kw; +use syntax::tokenstream; + +use syntax_pos::Span; + +use rustc_data_structures::sync::Lrc; + +/// 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(super) fn parse( + input: tokenstream::TokenStream, + expect_matchers: bool, + sess: &ParseSess, +) -> 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(); + 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, + ); + match tree { + TokenTree::MetaVar(start_sp, ident) if expect_matchers => { + let span = match trees.next() { + Some(tokenstream::TokenTree::Token(Token { kind: token::Colon, span })) => { + match trees.next() { + Some(tokenstream::TokenTree::Token(token)) => match token.ident() { + Some((kind, _)) => { + let span = token.span.with_lo(start_sp.lo()); + result.push(TokenTree::MetaVarDecl(span, ident, kind)); + continue; + } + _ => token.span, + }, + 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, ast::Ident::invalid())); + } + + // 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( + tree: tokenstream::TokenTree, + trees: &mut impl Iterator<Item = tokenstream::TokenTree>, + expect_matchers: bool, + sess: &ParseSess, +) -> 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 }) => 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. `$(pat)*`). + Some(tokenstream::TokenTree::Delimited(span, delim, tts)) => { + // Must have `(` not `{` or `[` + if delim != token::Paren { + let tok = pprust::token_kind_to_string(&token::OpenDelim(delim)); + let msg = format!("expected `(`, found `{}`", tok); + sess.span_diagnostic.span_err(span.entire(), &msg); + } + // Parse the contents of the sequence itself + let sequence = parse( + tts.into(), + expect_matchers, + sess, + ); + // Get the Kleene operator and optional separator + let (separator, kleene) = parse_sep_and_kleene_op(trees, span.entire(), sess); + // Count the number of captured "names" (i.e., named metavars) + let name_captures = macro_parser::count_names(&sequence); + TokenTree::Sequence( + span, + Lrc::new(SequenceRepetition { + tts: sequence, + separator, + kleene, + num_captures: name_captures, + }), + ) + } + + // `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate` special + // metavariable that names the crate of the invocation. + Some(tokenstream::TokenTree::Token(token)) if token.is_ident() => { + let (ident, is_raw) = token.ident().unwrap(); + let span = ident.span.with_lo(span.lo()); + if ident.name == kw::Crate && !is_raw { + TokenTree::token(token::Ident(kw::DollarCrate, is_raw), span) + } else { + TokenTree::MetaVar(span, ident) + } + } + + // `tree` is followed by a random token. This is an error. + Some(tokenstream::TokenTree::Token(token)) => { + let msg = + format!("expected identifier, found `{}`", pprust::token_to_string(&token),); + sess.span_diagnostic.span_err(token.span, &msg); + TokenTree::MetaVar(token.span, ast::Ident::invalid()) + } + + // There are no more tokens. Just return the `$` we already have. + None => TokenTree::token(token::Dollar, span), + }, + + // `tree` is an arbitrary token. Keep it. + tokenstream::TokenTree::Token(token) => TokenTree::Token(token), + + // `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, delim, tts) => TokenTree::Delimited( + span, + Lrc::new(Delimited { + delim, + tts: parse( + tts.into(), + expect_matchers, + sess, + ), + }), + ), + } +} + +/// 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( + input: &mut impl Iterator<Item = tokenstream::TokenTree>, + span: Span, +) -> Result<Result<(KleeneOp, Span), Token>, Span> { + match input.next() { + Some(tokenstream::TokenTree::Token(token)) => match kleene_op(&token) { + Some(op) => Ok(Ok((op, token.span))), + None => Ok(Err(token)), + }, + 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( + input: &mut impl Iterator<Item = tokenstream::TokenTree>, + span: Span, + sess: &ParseSess, +) -> (Option<Token>, KleeneToken) { + // 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 + 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(input, token.span) { + // #2 is the `?` Kleene op, which does not take a separator (error) + Ok(Ok((KleeneOp::ZeroOrOne, span))) => { + // Error! + sess.span_diagnostic.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.span_diagnostic.span_err(span, "expected one of: `*`, `+`, or `?`"); + + // Return a dummy + (None, KleeneToken::new(KleeneOp::ZeroOrMore, span)) +} |