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Rollup merge of #64689 - matklad:refactor-mbe, r=petrochenkov
Refactor macro by example This doesn't do anything useful yet, and just moves code around and restricts visibility
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,166 @@ | ||
| //! 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". | ||
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| crate mod transcribe; | ||
| crate mod macro_check; | ||
| crate mod macro_parser; | ||
| crate mod macro_rules; | ||
| crate mod quoted; | ||
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| use crate::ast; | ||
| use crate::parse::token::{self, Token, TokenKind}; | ||
| use crate::tokenstream::{DelimSpan}; | ||
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| use syntax_pos::{BytePos, Span}; | ||
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| use rustc_data_structures::sync::Lrc; | ||
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| /// 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>, | ||
| } | ||
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| impl Delimited { | ||
| /// Returns a `self::TokenTree` with a `Span` corresponding to the opening delimiter. | ||
| fn open_tt(&self, span: Span) -> TokenTree { | ||
| let open_span = if span.is_dummy() { | ||
| span | ||
| } else { | ||
| span.with_hi(span.lo() + BytePos(self.delim.len() as u32)) | ||
| }; | ||
| TokenTree::token(token::OpenDelim(self.delim), open_span) | ||
| } | ||
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| /// Returns a `self::TokenTree` with a `Span` corresponding to the closing delimiter. | ||
| fn close_tt(&self, span: Span) -> TokenTree { | ||
| let close_span = if span.is_dummy() { | ||
| span | ||
| } else { | ||
| span.with_lo(span.hi() - BytePos(self.delim.len() as u32)) | ||
| }; | ||
| TokenTree::token(token::CloseDelim(self.delim), close_span) | ||
| } | ||
| } | ||
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| #[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, | ||
| } | ||
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| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, Copy)] | ||
| struct KleeneToken { | ||
| span: Span, | ||
| op: KleeneOp, | ||
| } | ||
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| impl KleeneToken { | ||
| fn new(op: KleeneOp, span: Span) -> KleeneToken { | ||
| KleeneToken { span, op } | ||
| } | ||
| } | ||
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| /// A Kleene-style [repetition operator](http://en.wikipedia.org/wiki/Kleene_star) | ||
| /// for token sequences. | ||
| #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, 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, | ||
| } | ||
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| /// 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 */ | ||
| ), | ||
| } | ||
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| 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, | ||
| } | ||
| } | ||
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| /// Returns `true` if the given token tree is delimited. | ||
| fn is_delimited(&self) -> bool { | ||
| match *self { | ||
| TokenTree::Delimited(..) => true, | ||
| _ => false, | ||
| } | ||
| } | ||
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| /// 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, | ||
| } | ||
| } | ||
|
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| /// 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.open); | ||
| } | ||
| if index == delimed.tts.len() + 1 { | ||
| return delimed.close_tt(span.close); | ||
| } | ||
| delimed.tts[index - 1].clone() | ||
| } | ||
| (&TokenTree::Sequence(_, ref seq), _) => seq.tts[index].clone(), | ||
| _ => panic!("Cannot expand a token tree"), | ||
| } | ||
| } | ||
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| /// 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(), | ||
| } | ||
| } | ||
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| fn token(kind: TokenKind, span: Span) -> TokenTree { | ||
| TokenTree::Token(Token::new(kind, span)) | ||
| } | ||
| } |
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