| use crate::base::ExtCtxt; |
| use crate::errors::{ |
| CountRepetitionMisplaced, MetaVarExprUnrecognizedVar, MetaVarsDifSeqMatchers, MustRepeatOnce, |
| NoSyntaxVarsExprRepeat, VarStillRepeating, |
| }; |
| use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, MatchedTokenTree, NamedMatch}; |
| use crate::mbe::{self, MetaVarExpr}; |
| use rustc_ast::mut_visit::{self, MutVisitor}; |
| use rustc_ast::token::{self, Delimiter, Token, TokenKind}; |
| use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree}; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_errors::{pluralize, PResult}; |
| use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed}; |
| use rustc_span::hygiene::{LocalExpnId, Transparency}; |
| use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent}; |
| use rustc_span::Span; |
| |
| use smallvec::{smallvec, SmallVec}; |
| use std::mem; |
| |
| // A Marker adds the given mark to the syntax context. |
| struct Marker(LocalExpnId, Transparency); |
| |
| impl MutVisitor for Marker { |
| const VISIT_TOKENS: bool = true; |
| |
| fn visit_span(&mut self, span: &mut Span) { |
| *span = span.apply_mark(self.0.to_expn_id(), self.1) |
| } |
| } |
| |
| /// An iterator over the token trees in a delimited token tree (`{ ... }`) or a sequence (`$(...)`). |
| enum Frame<'a> { |
| Delimited { tts: &'a [mbe::TokenTree], idx: usize, delim: Delimiter, span: DelimSpan }, |
| Sequence { tts: &'a [mbe::TokenTree], idx: usize, sep: Option<Token> }, |
| } |
| |
| impl<'a> Frame<'a> { |
| /// Construct a new frame around the delimited set of tokens. |
| fn new(src: &'a mbe::Delimited, span: DelimSpan) -> Frame<'a> { |
| Frame::Delimited { tts: &src.tts, idx: 0, delim: src.delim, span } |
| } |
| } |
| |
| impl<'a> Iterator for Frame<'a> { |
| type Item = &'a mbe::TokenTree; |
| |
| fn next(&mut self) -> Option<&'a mbe::TokenTree> { |
| match self { |
| Frame::Delimited { tts, idx, .. } | Frame::Sequence { tts, idx, .. } => { |
| let res = tts.get(*idx); |
| *idx += 1; |
| res |
| } |
| } |
| } |
| } |
| |
| /// This can do Macro-By-Example transcription. |
| /// - `interp` is a map of meta-variables to the tokens (non-terminals) they matched in the |
| /// invocation. We are assuming we already know there is a match. |
| /// - `src` is the RHS of the MBE, that is, the "example" we are filling in. |
| /// |
| /// For example, |
| /// |
| /// ```rust |
| /// macro_rules! foo { |
| /// ($id:ident) => { println!("{}", stringify!($id)); } |
| /// } |
| /// |
| /// foo!(bar); |
| /// ``` |
| /// |
| /// `interp` would contain `$id => bar` and `src` would contain `println!("{}", stringify!($id));`. |
| /// |
| /// `transcribe` would return a `TokenStream` containing `println!("{}", stringify!(bar));`. |
| /// |
| /// Along the way, we do some additional error checking. |
| pub(super) fn transcribe<'a>( |
| cx: &ExtCtxt<'a>, |
| interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>, |
| src: &mbe::Delimited, |
| src_span: DelimSpan, |
| transparency: Transparency, |
| ) -> PResult<'a, TokenStream> { |
| // Nothing for us to transcribe... |
| if src.tts.is_empty() { |
| return Ok(TokenStream::default()); |
| } |
| |
| // We descend into the RHS (`src`), expanding things as we go. This stack contains the things |
| // we have yet to expand/are still expanding. We start the stack off with the whole RHS. |
| let mut stack: SmallVec<[Frame<'_>; 1]> = smallvec![Frame::new(&src, src_span)]; |
| |
| // As we descend in the RHS, we will need to be able to match nested sequences of matchers. |
| // `repeats` keeps track of where we are in matching at each level, with the last element being |
| // the most deeply nested sequence. This is used as a stack. |
| let mut repeats = Vec::new(); |
| |
| // `result` contains resulting token stream from the TokenTree we just finished processing. At |
| // the end, this will contain the full result of transcription, but at arbitrary points during |
| // `transcribe`, `result` will contain subsets of the final result. |
| // |
| // Specifically, as we descend into each TokenTree, we will push the existing results onto the |
| // `result_stack` and clear `results`. We will then produce the results of transcribing the |
| // TokenTree into `results`. Then, as we unwind back out of the `TokenTree`, we will pop the |
| // `result_stack` and append `results` too it to produce the new `results` up to that point. |
| // |
| // Thus, if we try to pop the `result_stack` and it is empty, we have reached the top-level |
| // again, and we are done transcribing. |
| let mut result: Vec<TokenTree> = Vec::new(); |
| let mut result_stack = Vec::new(); |
| let mut marker = Marker(cx.current_expansion.id, transparency); |
| |
| loop { |
| // Look at the last frame on the stack. |
| // If it still has a TokenTree we have not looked at yet, use that tree. |
| let Some(tree) = stack.last_mut().unwrap().next() else { |
| // This else-case never produces a value for `tree` (it `continue`s or `return`s). |
| |
| // Otherwise, if we have just reached the end of a sequence and we can keep repeating, |
| // go back to the beginning of the sequence. |
| if let Frame::Sequence { idx, sep, .. } = stack.last_mut().unwrap() { |
| let (repeat_idx, repeat_len) = repeats.last_mut().unwrap(); |
| *repeat_idx += 1; |
| if repeat_idx < repeat_len { |
| *idx = 0; |
| if let Some(sep) = sep { |
| result.push(TokenTree::Token(sep.clone(), Spacing::Alone)); |
| } |
| continue; |
| } |
| } |
| |
| // We are done with the top of the stack. Pop it. Depending on what it was, we do |
| // different things. Note that the outermost item must be the delimited, wrapped RHS |
| // that was passed in originally to `transcribe`. |
| match stack.pop().unwrap() { |
| // Done with a sequence. Pop from repeats. |
| Frame::Sequence { .. } => { |
| repeats.pop(); |
| } |
| |
| // We are done processing a Delimited. If this is the top-level delimited, we are |
| // done. Otherwise, we unwind the result_stack to append what we have produced to |
| // any previous results. |
| Frame::Delimited { delim, span, .. } => { |
| if result_stack.is_empty() { |
| // No results left to compute! We are back at the top-level. |
| return Ok(TokenStream::new(result)); |
| } |
| |
| // Step back into the parent Delimited. |
| let tree = TokenTree::Delimited(span, delim, TokenStream::new(result)); |
| result = result_stack.pop().unwrap(); |
| result.push(tree); |
| } |
| } |
| continue; |
| }; |
| |
| // At this point, we know we are in the middle of a TokenTree (the last one on `stack`). |
| // `tree` contains the next `TokenTree` to be processed. |
| match tree { |
| // We are descending into a sequence. We first make sure that the matchers in the RHS |
| // and the matches in `interp` have the same shape. Otherwise, either the caller or the |
| // macro writer has made a mistake. |
| seq @ mbe::TokenTree::Sequence(_, delimited) => { |
| match lockstep_iter_size(&seq, interp, &repeats) { |
| LockstepIterSize::Unconstrained => { |
| return Err(cx.create_err(NoSyntaxVarsExprRepeat { span: seq.span() })); |
| } |
| |
| LockstepIterSize::Contradiction(msg) => { |
| // FIXME: this really ought to be caught at macro definition time... It |
| // happens when two meta-variables are used in the same repetition in a |
| // sequence, but they come from different sequence matchers and repeat |
| // different amounts. |
| return Err(cx.create_err(MetaVarsDifSeqMatchers { span: seq.span(), msg })); |
| } |
| |
| LockstepIterSize::Constraint(len, _) => { |
| // We do this to avoid an extra clone above. We know that this is a |
| // sequence already. |
| let mbe::TokenTree::Sequence(sp, seq) = seq else { |
| unreachable!() |
| }; |
| |
| // Is the repetition empty? |
| if len == 0 { |
| if seq.kleene.op == mbe::KleeneOp::OneOrMore { |
| // FIXME: this really ought to be caught at macro definition |
| // time... It happens when the Kleene operator in the matcher and |
| // the body for the same meta-variable do not match. |
| return Err(cx.create_err(MustRepeatOnce { span: sp.entire() })); |
| } |
| } else { |
| // 0 is the initial counter (we have done 0 repetitions so far). `len` |
| // is the total number of repetitions we should generate. |
| repeats.push((0, len)); |
| |
| // The first time we encounter the sequence we push it to the stack. It |
| // then gets reused (see the beginning of the loop) until we are done |
| // repeating. |
| stack.push(Frame::Sequence { |
| idx: 0, |
| sep: seq.separator.clone(), |
| tts: &delimited.tts, |
| }); |
| } |
| } |
| } |
| } |
| |
| // Replace the meta-var with the matched token tree from the invocation. |
| mbe::TokenTree::MetaVar(mut sp, mut original_ident) => { |
| // Find the matched nonterminal from the macro invocation, and use it to replace |
| // the meta-var. |
| let ident = MacroRulesNormalizedIdent::new(original_ident); |
| if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) { |
| match cur_matched { |
| MatchedTokenTree(tt) => { |
| // `tt`s are emitted into the output stream directly as "raw tokens", |
| // without wrapping them into groups. |
| let token = tt.clone(); |
| result.push(token); |
| } |
| MatchedNonterminal(nt) => { |
| // Other variables are emitted into the output stream as groups with |
| // `Delimiter::Invisible` to maintain parsing priorities. |
| // `Interpolated` is currently used for such groups in rustc parser. |
| marker.visit_span(&mut sp); |
| let token = TokenTree::token_alone(token::Interpolated(nt.clone()), sp); |
| result.push(token); |
| } |
| MatchedSeq(..) => { |
| // We were unable to descend far enough. This is an error. |
| return Err(cx.create_err(VarStillRepeating { span: sp, ident })); |
| } |
| } |
| } else { |
| // If we aren't able to match the meta-var, we push it back into the result but |
| // with modified syntax context. (I believe this supports nested macros). |
| marker.visit_span(&mut sp); |
| marker.visit_ident(&mut original_ident); |
| result.push(TokenTree::token_alone(token::Dollar, sp)); |
| result.push(TokenTree::Token( |
| Token::from_ast_ident(original_ident), |
| Spacing::Alone, |
| )); |
| } |
| } |
| |
| // Replace meta-variable expressions with the result of their expansion. |
| mbe::TokenTree::MetaVarExpr(sp, expr) => { |
| transcribe_metavar_expr(cx, expr, interp, &mut marker, &repeats, &mut result, &sp)?; |
| } |
| |
| // If we are entering a new delimiter, we push its contents to the `stack` to be |
| // processed, and we push all of the currently produced results to the `result_stack`. |
| // We will produce all of the results of the inside of the `Delimited` and then we will |
| // jump back out of the Delimited, pop the result_stack and add the new results back to |
| // the previous results (from outside the Delimited). |
| mbe::TokenTree::Delimited(mut span, delimited) => { |
| mut_visit::visit_delim_span(&mut span, &mut marker); |
| stack.push(Frame::Delimited { |
| tts: &delimited.tts, |
| delim: delimited.delim, |
| idx: 0, |
| span, |
| }); |
| result_stack.push(mem::take(&mut result)); |
| } |
| |
| // Nothing much to do here. Just push the token to the result, being careful to |
| // preserve syntax context. |
| mbe::TokenTree::Token(token) => { |
| let mut token = token.clone(); |
| mut_visit::visit_token(&mut token, &mut marker); |
| let tt = TokenTree::Token(token, Spacing::Alone); |
| result.push(tt); |
| } |
| |
| // There should be no meta-var declarations in the invocation of a macro. |
| mbe::TokenTree::MetaVarDecl(..) => panic!("unexpected `TokenTree::MetaVarDecl`"), |
| } |
| } |
| } |
| |
| /// Lookup the meta-var named `ident` and return the matched token tree from the invocation using |
| /// the set of matches `interpolations`. |
| /// |
| /// See the definition of `repeats` in the `transcribe` function. `repeats` is used to descend |
| /// into the right place in nested matchers. If we attempt to descend too far, the macro writer has |
| /// made a mistake, and we return `None`. |
| fn lookup_cur_matched<'a>( |
| ident: MacroRulesNormalizedIdent, |
| interpolations: &'a FxHashMap<MacroRulesNormalizedIdent, NamedMatch>, |
| repeats: &[(usize, usize)], |
| ) -> Option<&'a NamedMatch> { |
| interpolations.get(&ident).map(|mut matched| { |
| for &(idx, _) in repeats { |
| match matched { |
| MatchedTokenTree(_) | MatchedNonterminal(_) => break, |
| MatchedSeq(ads) => matched = ads.get(idx).unwrap(), |
| } |
| } |
| |
| matched |
| }) |
| } |
| |
| /// An accumulator over a TokenTree to be used with `fold`. During transcription, we need to make |
| /// sure that the size of each sequence and all of its nested sequences are the same as the sizes |
| /// of all the matched (nested) sequences in the macro invocation. If they don't match, somebody |
| /// has made a mistake (either the macro writer or caller). |
| #[derive(Clone)] |
| enum LockstepIterSize { |
| /// No constraints on length of matcher. This is true for any TokenTree variants except a |
| /// `MetaVar` with an actual `MatchedSeq` (as opposed to a `MatchedNonterminal`). |
| Unconstrained, |
| |
| /// A `MetaVar` with an actual `MatchedSeq`. The length of the match and the name of the |
| /// meta-var are returned. |
| Constraint(usize, MacroRulesNormalizedIdent), |
| |
| /// Two `Constraint`s on the same sequence had different lengths. This is an error. |
| Contradiction(String), |
| } |
| |
| impl LockstepIterSize { |
| /// Find incompatibilities in matcher/invocation sizes. |
| /// - `Unconstrained` is compatible with everything. |
| /// - `Contradiction` is incompatible with everything. |
| /// - `Constraint(len)` is only compatible with other constraints of the same length. |
| fn with(self, other: LockstepIterSize) -> LockstepIterSize { |
| match self { |
| LockstepIterSize::Unconstrained => other, |
| LockstepIterSize::Contradiction(_) => self, |
| LockstepIterSize::Constraint(l_len, l_id) => match other { |
| LockstepIterSize::Unconstrained => self, |
| LockstepIterSize::Contradiction(_) => other, |
| LockstepIterSize::Constraint(r_len, _) if l_len == r_len => self, |
| LockstepIterSize::Constraint(r_len, r_id) => { |
| let msg = format!( |
| "meta-variable `{}` repeats {} time{}, but `{}` repeats {} time{}", |
| l_id, |
| l_len, |
| pluralize!(l_len), |
| r_id, |
| r_len, |
| pluralize!(r_len), |
| ); |
| LockstepIterSize::Contradiction(msg) |
| } |
| }, |
| } |
| } |
| } |
| |
| /// Given a `tree`, make sure that all sequences have the same length as the matches for the |
| /// appropriate meta-vars in `interpolations`. |
| /// |
| /// Note that if `repeats` does not match the exact correct depth of a meta-var, |
| /// `lookup_cur_matched` will return `None`, which is why this still works even in the presence of |
| /// multiple nested matcher sequences. |
| /// |
| /// Example: `$($($x $y)+*);+` -- we need to make sure that `x` and `y` repeat the same amount as |
| /// each other at the given depth when the macro was invoked. If they don't it might mean they were |
| /// declared at depths which weren't equal or there was a compiler bug. For example, if we have 3 repetitions of |
| /// the outer sequence and 4 repetitions of the inner sequence for `x`, we should have the same for |
| /// `y`; otherwise, we can't transcribe them both at the given depth. |
| fn lockstep_iter_size( |
| tree: &mbe::TokenTree, |
| interpolations: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>, |
| repeats: &[(usize, usize)], |
| ) -> LockstepIterSize { |
| use mbe::TokenTree; |
| match tree { |
| TokenTree::Delimited(_, delimited) => { |
| delimited.tts.iter().fold(LockstepIterSize::Unconstrained, |size, tt| { |
| size.with(lockstep_iter_size(tt, interpolations, repeats)) |
| }) |
| } |
| TokenTree::Sequence(_, seq) => { |
| seq.tts.iter().fold(LockstepIterSize::Unconstrained, |size, tt| { |
| size.with(lockstep_iter_size(tt, interpolations, repeats)) |
| }) |
| } |
| TokenTree::MetaVar(_, name) | TokenTree::MetaVarDecl(_, name, _) => { |
| let name = MacroRulesNormalizedIdent::new(*name); |
| match lookup_cur_matched(name, interpolations, repeats) { |
| Some(matched) => match matched { |
| MatchedTokenTree(_) | MatchedNonterminal(_) => LockstepIterSize::Unconstrained, |
| MatchedSeq(ads) => LockstepIterSize::Constraint(ads.len(), name), |
| }, |
| _ => LockstepIterSize::Unconstrained, |
| } |
| } |
| TokenTree::MetaVarExpr(_, expr) => { |
| let default_rslt = LockstepIterSize::Unconstrained; |
| let Some(ident) = expr.ident() else { return default_rslt; }; |
| let name = MacroRulesNormalizedIdent::new(ident); |
| match lookup_cur_matched(name, interpolations, repeats) { |
| Some(MatchedSeq(ads)) => { |
| default_rslt.with(LockstepIterSize::Constraint(ads.len(), name)) |
| } |
| _ => default_rslt, |
| } |
| } |
| TokenTree::Token(..) => LockstepIterSize::Unconstrained, |
| } |
| } |
| |
| /// Used solely by the `count` meta-variable expression, counts the outer-most repetitions at a |
| /// given optional nested depth. |
| /// |
| /// For example, a macro parameter of `$( { $( $foo:ident ),* } )*` called with `{ a, b } { c }`: |
| /// |
| /// * `[ $( ${count(foo)} ),* ]` will return [2, 1] with a, b = 2 and c = 1 |
| /// * `[ $( ${count(foo, 0)} ),* ]` will be the same as `[ $( ${count(foo)} ),* ]` |
| /// * `[ $( ${count(foo, 1)} ),* ]` will return an error because `${count(foo, 1)}` is |
| /// declared inside a single repetition and the index `1` implies two nested repetitions. |
| fn count_repetitions<'a>( |
| cx: &ExtCtxt<'a>, |
| depth_opt: Option<usize>, |
| mut matched: &NamedMatch, |
| repeats: &[(usize, usize)], |
| sp: &DelimSpan, |
| ) -> PResult<'a, usize> { |
| // Recursively count the number of matches in `matched` at given depth |
| // (or at the top-level of `matched` if no depth is given). |
| fn count<'a>( |
| cx: &ExtCtxt<'a>, |
| declared_lhs_depth: usize, |
| depth_opt: Option<usize>, |
| matched: &NamedMatch, |
| sp: &DelimSpan, |
| ) -> PResult<'a, usize> { |
| match matched { |
| MatchedTokenTree(_) | MatchedNonterminal(_) => { |
| if declared_lhs_depth == 0 { |
| return Err(cx.create_err(CountRepetitionMisplaced { span: sp.entire() })); |
| } |
| match depth_opt { |
| None => Ok(1), |
| Some(_) => Err(out_of_bounds_err(cx, declared_lhs_depth, sp.entire(), "count")), |
| } |
| } |
| MatchedSeq(named_matches) => { |
| let new_declared_lhs_depth = declared_lhs_depth + 1; |
| match depth_opt { |
| None => named_matches |
| .iter() |
| .map(|elem| count(cx, new_declared_lhs_depth, None, elem, sp)) |
| .sum(), |
| Some(0) => Ok(named_matches.len()), |
| Some(depth) => named_matches |
| .iter() |
| .map(|elem| count(cx, new_declared_lhs_depth, Some(depth - 1), elem, sp)) |
| .sum(), |
| } |
| } |
| } |
| } |
| // `repeats` records all of the nested levels at which we are currently |
| // matching meta-variables. The meta-var-expr `count($x)` only counts |
| // matches that occur in this "subtree" of the `NamedMatch` where we |
| // are currently transcribing, so we need to descend to that subtree |
| // before we start counting. `matched` contains the various levels of the |
| // tree as we descend, and its final value is the subtree we are currently at. |
| for &(idx, _) in repeats { |
| if let MatchedSeq(ads) = matched { |
| matched = &ads[idx]; |
| } |
| } |
| count(cx, 0, depth_opt, matched, sp) |
| } |
| |
| /// Returns a `NamedMatch` item declared on the LHS given an arbitrary [Ident] |
| fn matched_from_ident<'ctx, 'interp, 'rslt>( |
| cx: &ExtCtxt<'ctx>, |
| ident: Ident, |
| interp: &'interp FxHashMap<MacroRulesNormalizedIdent, NamedMatch>, |
| ) -> PResult<'ctx, &'rslt NamedMatch> |
| where |
| 'interp: 'rslt, |
| { |
| let span = ident.span; |
| let key = MacroRulesNormalizedIdent::new(ident); |
| interp.get(&key).ok_or_else(|| cx.create_err(MetaVarExprUnrecognizedVar { span, key })) |
| } |
| |
| /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For |
| /// example, index(999999) in an repetition of only three elements. |
| fn out_of_bounds_err<'a>( |
| cx: &ExtCtxt<'a>, |
| max: usize, |
| span: Span, |
| ty: &str, |
| ) -> DiagnosticBuilder<'a, ErrorGuaranteed> { |
| let msg = if max == 0 { |
| format!( |
| "meta-variable expression `{ty}` with depth parameter \ |
| must be called inside of a macro repetition" |
| ) |
| } else { |
| format!( |
| "depth parameter on meta-variable expression `{ty}` \ |
| must be less than {max}" |
| ) |
| }; |
| cx.struct_span_err(span, msg) |
| } |
| |
| fn transcribe_metavar_expr<'a>( |
| cx: &ExtCtxt<'a>, |
| expr: &MetaVarExpr, |
| interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>, |
| marker: &mut Marker, |
| repeats: &[(usize, usize)], |
| result: &mut Vec<TokenTree>, |
| sp: &DelimSpan, |
| ) -> PResult<'a, ()> { |
| let mut visited_span = || { |
| let mut span = sp.entire(); |
| marker.visit_span(&mut span); |
| span |
| }; |
| match *expr { |
| MetaVarExpr::Count(original_ident, depth_opt) => { |
| let matched = matched_from_ident(cx, original_ident, interp)?; |
| let count = count_repetitions(cx, depth_opt, matched, &repeats, sp)?; |
| let tt = TokenTree::token_alone( |
| TokenKind::lit(token::Integer, sym::integer(count), None), |
| visited_span(), |
| ); |
| result.push(tt); |
| } |
| MetaVarExpr::Ignore(original_ident) => { |
| // Used to ensure that `original_ident` is present in the LHS |
| let _ = matched_from_ident(cx, original_ident, interp)?; |
| } |
| MetaVarExpr::Index(depth) => match repeats.iter().nth_back(depth) { |
| Some((index, _)) => { |
| result.push(TokenTree::token_alone( |
| TokenKind::lit(token::Integer, sym::integer(*index), None), |
| visited_span(), |
| )); |
| } |
| None => return Err(out_of_bounds_err(cx, repeats.len(), sp.entire(), "index")), |
| }, |
| MetaVarExpr::Length(depth) => match repeats.iter().nth_back(depth) { |
| Some((_, length)) => { |
| result.push(TokenTree::token_alone( |
| TokenKind::lit(token::Integer, sym::integer(*length), None), |
| visited_span(), |
| )); |
| } |
| None => return Err(out_of_bounds_err(cx, repeats.len(), sp.entire(), "length")), |
| }, |
| } |
| Ok(()) |
| } |
