| //! This module implements declarative macros: old `macro_rules` and the newer |
| //! `macro`. Declarative macros are also known as "macro by example", and that's |
| //! why we call this module `mbe`. For external documentation, prefer the |
| //! official terminology: "declarative macros". |
| |
| crate mod transcribe; |
| crate mod macro_check; |
| crate mod macro_parser; |
| crate mod macro_rules; |
| crate mod quoted; |
| |
| use syntax::ast; |
| use syntax::token::{self, Token, TokenKind}; |
| use syntax::tokenstream::{DelimSpan}; |
| |
| use syntax_pos::Span; |
| |
| use rustc_data_structures::sync::Lrc; |
| |
| /// 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)] |
| struct Delimited { |
| delim: token::DelimToken, |
| tts: Vec<TokenTree>, |
| } |
| |
| impl Delimited { |
| /// Returns a `self::TokenTree` with a `Span` corresponding to the opening delimiter. |
| fn open_tt(&self, span: DelimSpan) -> TokenTree { |
| TokenTree::token(token::OpenDelim(self.delim), span.open) |
| } |
| |
| /// Returns a `self::TokenTree` with a `Span` corresponding to the closing delimiter. |
| fn close_tt(&self, span: DelimSpan) -> TokenTree { |
| TokenTree::token(token::CloseDelim(self.delim), span.close) |
| } |
| } |
| |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug)] |
| struct SequenceRepetition { |
| /// The sequence of token trees |
| tts: Vec<TokenTree>, |
| /// The optional separator |
| separator: Option<Token>, |
| /// Whether the sequence can be repeated zero (*), or one or more times (+) |
| kleene: KleeneToken, |
| /// The number of `Match`s that appear in the sequence (and subsequences) |
| num_captures: usize, |
| } |
| |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)] |
| struct KleeneToken { |
| span: Span, |
| op: KleeneOp, |
| } |
| |
| impl KleeneToken { |
| fn new(op: KleeneOp, span: Span) -> KleeneToken { |
| KleeneToken { span, op } |
| } |
| } |
| |
| /// A Kleene-style [repetition operator](http://en.wikipedia.org/wiki/Kleene_star) |
| /// for token sequences. |
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)] |
| enum KleeneOp { |
| /// Kleene star (`*`) for zero or more repetitions |
| ZeroOrMore, |
| /// Kleene plus (`+`) for one or more repetitions |
| OneOrMore, |
| /// Kleene optional (`?`) for zero or one reptitions |
| ZeroOrOne, |
| } |
| |
| /// Similar to `tokenstream::TokenTree`, except that `$i`, `$i:ident`, and `$(...)` |
| /// are "first-class" token trees. Useful for parsing macros. |
| #[derive(Debug, Clone, PartialEq, RustcEncodable, RustcDecodable)] |
| enum TokenTree { |
| Token(Token), |
| Delimited(DelimSpan, Lrc<Delimited>), |
| /// A kleene-style repetition sequence |
| Sequence(DelimSpan, Lrc<SequenceRepetition>), |
| /// e.g., `$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. |
| 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 is delimited. |
| fn is_delimited(&self) -> bool { |
| match *self { |
| TokenTree::Delimited(..) => true, |
| _ => false, |
| } |
| } |
| |
| /// Returns `true` if the given token tree is a token of the given kind. |
| fn is_token(&self, expected_kind: &TokenKind) -> bool { |
| match self { |
| TokenTree::Token(Token { kind: actual_kind, .. }) => actual_kind == expected_kind, |
| _ => false, |
| } |
| } |
| |
| /// Gets the `index`-th sub-token-tree. This only makes sense for delimited trees and sequences. |
| 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); |
| } |
| if index == delimed.tts.len() + 1 { |
| return delimed.close_tt(span); |
| } |
| delimed.tts[index - 1].clone() |
| } |
| (&TokenTree::Sequence(_, ref seq), _) => seq.tts[index].clone(), |
| _ => panic!("Cannot expand a token tree"), |
| } |
| } |
| |
| /// Retrieves the `TokenTree`'s span. |
| fn span(&self) -> Span { |
| match *self { |
| TokenTree::Token(Token { span, .. }) |
| | TokenTree::MetaVar(span, _) |
| | TokenTree::MetaVarDecl(span, _, _) => span, |
| TokenTree::Delimited(span, _) | TokenTree::Sequence(span, _) => span.entire(), |
| } |
| } |
| |
| fn token(kind: TokenKind, span: Span) -> TokenTree { |
| TokenTree::Token(Token::new(kind, span)) |
| } |
| } |