diff options
Diffstat (limited to 'compiler/rustc_expand/src/mbe/quoted.rs')
| -rw-r--r-- | compiler/rustc_expand/src/mbe/quoted.rs | 366 |
1 files changed, 366 insertions, 0 deletions
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs new file mode 100644 index 000000000..ee17d54f6 --- /dev/null +++ b/compiler/rustc_expand/src/mbe/quoted.rs @@ -0,0 +1,366 @@ +use crate::mbe::macro_parser::count_metavar_decls; +use crate::mbe::{Delimited, KleeneOp, KleeneToken, MetaVarExpr, SequenceRepetition, TokenTree}; + +use rustc_ast::token::{self, Delimiter, Token}; +use rustc_ast::{tokenstream, NodeId}; +use rustc_ast_pretty::pprust; +use rustc_feature::Features; +use rustc_session::parse::{feature_err, ParseSess}; +use rustc_span::symbol::{kw, sym, Ident}; + +use rustc_span::edition::Edition; +use rustc_span::{Span, SyntaxContext}; + +const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \ + `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \ + `literal`, `path`, `meta`, `tt`, `item` and `vis`"; + +/// 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: &ParseSess, + 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 trees = input.into_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, parsing_patterns, sess, node_id, features, edition); + match tree { + TokenTree::MetaVar(start_sp, ident) if parsing_patterns => { + 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((frag, _)) => { + let span = token.span.with_lo(start_sp.lo()); + + let kind = + token::NonterminalKind::from_symbol(frag.name, || { + // 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.ctxt() == SyntaxContext::root() { + edition + } else { + span.edition() + } + }) + .unwrap_or_else( + || { + let msg = format!( + "invalid fragment specifier `{}`", + frag.name + ); + sess.span_diagnostic + .struct_span_err(span, &msg) + .help(VALID_FRAGMENT_NAMES_MSG) + .emit(); + token::NonterminalKind::Ident + }, + ); + result.push(TokenTree::MetaVarDecl(span, ident, Some(kind))); + continue; + } + _ => token.span, + }, + tree => tree.as_ref().map_or(span, tokenstream::TokenTree::span), + } + } + tree => tree.as_ref().map_or(start_sp, tokenstream::TokenTree::span), + }; + + 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 already declared +fn maybe_emit_macro_metavar_expr_feature(features: &Features, sess: &ParseSess, span: Span) { + if !features.macro_metavar_expr { + let msg = "meta-variable expressions are unstable"; + feature_err(&sess, sym::macro_metavar_expr, 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_trees`: 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( + tree: tokenstream::TokenTree, + outer_trees: &mut impl Iterator<Item = tokenstream::TokenTree>, + parsing_patterns: bool, + sess: &ParseSess, + 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 }, _) => { + // FIXME: Handle `Invisible`-delimited groups in a more systematic way + // during parsing. + let mut next = outer_trees.next(); + let mut trees: Box<dyn Iterator<Item = tokenstream::TokenTree>>; + if let Some(tokenstream::TokenTree::Delimited(_, Delimiter::Invisible, tts)) = next { + trees = Box::new(tts.into_trees()); + next = trees.next(); + } else { + trees = Box::new(outer_trees); + } + + match next { + // `tree` is followed by a delimited set of token trees. + Some(tokenstream::TokenTree::Delimited(delim_span, delim, 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. `${count(ident)}`). + // Try to parse the meta-variable expression. + match MetaVarExpr::parse(&tts, delim_span.entire(), sess) { + Err(mut err) => { + err.emit(); + // Returns early the same read `$` to avoid spanning + // unrelated diagnostics that could be performed afterwards + return TokenTree::token(token::Dollar, span); + } + Ok(elem) => { + maybe_emit_macro_metavar_expr_feature( + features, + sess, + delim_span.entire(), + ); + return TokenTree::MetaVarExpr(delim_span, elem); + } + } + } + Delimiter::Parenthesis => {} + _ => { + let tok = pprust::token_kind_to_string(&token::OpenDelim(delim)); + let msg = format!("expected `(` or `{{`, found `{}`", tok); + sess.span_diagnostic.span_err(delim_span.entire(), &msg); + } + } + } + // If we didn't find a metavar expression above, then we must have a + // repetition sequence in the macro (e.g. `$(pat)*`). Parse the + // contents of the sequence itself + let sequence = parse(tts, parsing_patterns, sess, node_id, features, edition); + // Get the Kleene operator and optional separator + let (separator, kleene) = + parse_sep_and_kleene_op(&mut trees, delim_span.entire(), sess); + // Count the number of captured "names" (i.e., named metavars) + let num_captures = + if parsing_patterns { count_metavar_decls(&sequence) } else { 0 }; + TokenTree::Sequence( + delim_span, + SequenceRepetition { tts: sequence, separator, kleene, num_captures }, + ) + } + + // `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate` + // special metavariable that names the crate of the invocation. + Some(tokenstream::TokenTree::Token(token, _)) if token.is_ident() => { + let (ident, is_raw) = token.ident().unwrap(); + let span = ident.span.with_lo(span.lo()); + if ident.name == kw::Crate && !is_raw { + TokenTree::token(token::Ident(kw::DollarCrate, is_raw), span) + } else { + TokenTree::MetaVar(span, ident) + } + } + + // `tree` is followed by another `$`. This is an escaped `$`. + Some(tokenstream::TokenTree::Token(Token { kind: token::Dollar, span }, _)) => { + if parsing_patterns { + span_dollar_dollar_or_metavar_in_the_lhs_err( + sess, + &Token { kind: token::Dollar, span }, + ); + } else { + maybe_emit_macro_metavar_expr_feature(features, sess, span); + } + TokenTree::token(token::Dollar, span) + } + + // `tree` is followed by some other token. This is an error. + Some(tokenstream::TokenTree::Token(token, _)) => { + let msg = format!( + "expected identifier, found `{}`", + pprust::token_to_string(&token), + ); + sess.span_diagnostic.span_err(token.span, &msg); + TokenTree::MetaVar(token.span, Ident::empty()) + } + + // There are no more tokens. Just return the `$` we already have. + None => TokenTree::token(token::Dollar, 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, + 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( + 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_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 `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)) +} + +// `$$` or a meta-variable is the lhs of a macro but shouldn't. +// +// For example, `macro_rules! foo { ( ${length()} ) => {} }` +fn span_dollar_dollar_or_metavar_in_the_lhs_err<'sess>(sess: &'sess ParseSess, token: &Token) { + sess.span_diagnostic + .span_err(token.span, &format!("unexpected token: {}", pprust::token_to_string(token))); + sess.span_diagnostic.span_note_without_error( + token.span, + "`$$` and meta-variable expressions are not allowed inside macro parameter definitions", + ); +} |