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use std::mem;
use rustc_ast::mut_visit::{self, MutVisitor};
use rustc_ast::token::{self, Delimiter, IdentIsRaw, Lit, LitKind, Nonterminal, Token, TokenKind};
use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_ast::ExprKind;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::{pluralize, Diag, DiagCtxtHandle, PResult};
use rustc_parse::lexer::nfc_normalize;
use rustc_parse::parser::ParseNtResult;
use rustc_session::parse::{ParseSess, SymbolGallery};
use rustc_span::hygiene::{LocalExpnId, Transparency};
use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent};
use rustc_span::{with_metavar_spans, Span, Symbol, SyntaxContext};
use smallvec::{smallvec, SmallVec};
use crate::errors::{
CountRepetitionMisplaced, MetaVarExprUnrecognizedVar, MetaVarsDifSeqMatchers, MustRepeatOnce,
NoSyntaxVarsExprRepeat, VarStillRepeating,
};
use crate::mbe::macro_parser::NamedMatch;
use crate::mbe::macro_parser::NamedMatch::*;
use crate::mbe::metavar_expr::{MetaVarExprConcatElem, RAW_IDENT_ERR};
use crate::mbe::{self, KleeneOp, MetaVarExpr};
// A Marker adds the given mark to the syntax context.
struct Marker(LocalExpnId, Transparency, FxHashMap<SyntaxContext, SyntaxContext>);
impl MutVisitor for Marker {
const VISIT_TOKENS: bool = true;
fn visit_span(&mut self, span: &mut Span) {
// `apply_mark` is a relatively expensive operation, both due to taking hygiene lock, and
// by itself. All tokens in a macro body typically have the same syntactic context, unless
// it's some advanced case with macro-generated macros. So if we cache the marked version
// of that context once, we'll typically have a 100% cache hit rate after that.
let Marker(expn_id, transparency, ref mut cache) = *self;
*span = span.map_ctxt(|ctxt| {
*cache
.entry(ctxt)
.or_insert_with(|| ctxt.apply_mark(expn_id.to_expn_id(), transparency))
});
}
}
/// An iterator over the token trees in a delimited token tree (`{ ... }`) or a sequence (`$(...)`).
struct Frame<'a> {
tts: &'a [mbe::TokenTree],
idx: usize,
kind: FrameKind,
}
enum FrameKind {
Delimited { delim: Delimiter, span: DelimSpan, spacing: DelimSpacing },
Sequence { sep: Option<Token>, kleene_op: KleeneOp },
}
impl<'a> Frame<'a> {
fn new_delimited(src: &'a mbe::Delimited, span: DelimSpan, spacing: DelimSpacing) -> Frame<'a> {
Frame {
tts: &src.tts,
idx: 0,
kind: FrameKind::Delimited { delim: src.delim, span, spacing },
}
}
fn new_sequence(
src: &'a mbe::SequenceRepetition,
sep: Option<Token>,
kleene_op: KleeneOp,
) -> Frame<'a> {
Frame { tts: &src.tts, idx: 0, kind: FrameKind::Sequence { sep, kleene_op } }
}
}
impl<'a> Iterator for Frame<'a> {
type Item = &'a mbe::TokenTree;
fn next(&mut self) -> Option<&'a mbe::TokenTree> {
let res = self.tts.get(self.idx);
self.idx += 1;
res
}
}
/// This can do Macro-By-Example transcription.
/// - `interp` is a map of meta-variables to the tokens (non-terminals) they matched in the
/// invocation. We are assuming we already know there is a match.
/// - `src` is the RHS of the MBE, that is, the "example" we are filling in.
///
/// For example,
///
/// ```rust
/// macro_rules! foo {
/// ($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>(
psess: &'a ParseSess,
interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
src: &mbe::Delimited,
src_span: DelimSpan,
transparency: Transparency,
expand_id: LocalExpnId,
) -> 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. The
// choice of spacing values doesn't matter.
let mut stack: SmallVec<[Frame<'_>; 1]> = smallvec![Frame::new_delimited(
src,
src_span,
DelimSpacing::new(Spacing::Alone, Spacing::Alone)
)];
// 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<(usize, usize)> = 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(expand_id, transparency, Default::default());
let dcx = psess.dcx();
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.
let frame = stack.last_mut().unwrap();
if let FrameKind::Sequence { sep, .. } = &frame.kind {
let (repeat_idx, repeat_len) = repeats.last_mut().unwrap();
*repeat_idx += 1;
if repeat_idx < repeat_len {
frame.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().kind {
// Done with a sequence. Pop from repeats.
FrameKind::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.
FrameKind::Delimited { delim, span, mut spacing, .. } => {
// Hack to force-insert a space after `]` in certain case.
// See discussion of the `hex-literal` crate in #114571.
if delim == Delimiter::Bracket {
spacing.close = Spacing::Alone;
}
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, spacing, 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(_, seq_rep) => {
match lockstep_iter_size(seq, interp, &repeats) {
LockstepIterSize::Unconstrained => {
return Err(dcx.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(
dcx.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 == 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(dcx.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::new_sequence(
seq_rep,
seq.separator.clone(),
seq.kleene.op,
));
}
}
}
}
// 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.
//
// We use `Spacing::Alone` everywhere here, because that's the conservative choice
// and spacing of declarative macros is tricky. E.g. in this macro:
// ```
// macro_rules! idents {
// ($($a:ident,)*) => { stringify!($($a)*) }
// }
// ```
// `$a` has no whitespace after it and will be marked `JointHidden`. If you then
// call `idents!(x,y,z,)`, each of `x`, `y`, and `z` will be marked as `Joint`. So
// if you choose to use `$x`'s spacing or the identifier's spacing, you'll end up
// producing "xyz", which is bad because it effectively merges tokens.
// `Spacing::Alone` is the safer option. Fortunately, `space_between` will avoid
// some of the unnecessary whitespace.
let ident = MacroRulesNormalizedIdent::new(original_ident);
if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) {
let tt = match cur_matched {
MatchedSingle(ParseNtResult::Tt(tt)) => {
// `tt`s are emitted into the output stream directly as "raw tokens",
// without wrapping them into groups.
maybe_use_metavar_location(psess, &stack, sp, tt, &mut marker)
}
MatchedSingle(ParseNtResult::Ident(ident, is_raw)) => {
marker.visit_span(&mut sp);
let kind = token::NtIdent(*ident, *is_raw);
TokenTree::token_alone(kind, sp)
}
MatchedSingle(ParseNtResult::Lifetime(ident)) => {
marker.visit_span(&mut sp);
let kind = token::NtLifetime(*ident);
TokenTree::token_alone(kind, sp)
}
MatchedSingle(ParseNtResult::Nt(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);
TokenTree::token_alone(token::Interpolated(nt.clone()), sp)
}
MatchedSeq(..) => {
// We were unable to descend far enough. This is an error.
return Err(dcx.create_err(VarStillRepeating { span: sp, ident }));
}
};
result.push(tt)
} 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_joint_hidden(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(
dcx,
expr,
interp,
&mut marker,
&repeats,
&mut result,
sp,
&psess.symbol_gallery,
)?;
}
// 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, spacing, delimited) => {
mut_visit::visit_delim_span(&mut marker, &mut span);
stack.push(Frame::new_delimited(delimited, span, *spacing));
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 marker, &mut token);
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`"),
}
}
}
/// Store the metavariable span for this original span into a side table.
/// FIXME: Try to put the metavariable span into `SpanData` instead of a side table (#118517).
/// An optimal encoding for inlined spans will need to be selected to minimize regressions.
/// The side table approach is relatively good, but not perfect due to collisions.
/// In particular, collisions happen when token is passed as an argument through several macro
/// calls, like in recursive macros.
/// The old heuristic below is used to improve spans in case of collisions, but diagnostics are
/// still degraded sometimes in those cases.
///
/// The old heuristic:
///
/// Usually metavariables `$var` produce interpolated tokens, which have an additional place for
/// keeping both the original span and the metavariable span. For `tt` metavariables that's not the
/// case however, and there's no place for keeping a second span. So we try to give the single
/// produced span a location that would be most useful in practice (the hygiene part of the span
/// must not be changed).
///
/// Different locations are useful for different purposes:
/// - The original location is useful when we need to report a diagnostic for the original token in
/// isolation, without combining it with any surrounding tokens. This case occurs, but it is not
/// very common in practice.
/// - The metavariable location is useful when we need to somehow combine the token span with spans
/// of its surrounding tokens. This is the most common way to use token spans.
///
/// So this function replaces the original location with the metavariable location in all cases
/// except these two:
/// - The metavariable is an element of undelimited sequence `$($tt)*`.
/// These are typically used for passing larger amounts of code, and tokens in that code usually
/// combine with each other and not with tokens outside of the sequence.
/// - The metavariable span comes from a different crate, then we prefer the more local span.
fn maybe_use_metavar_location(
psess: &ParseSess,
stack: &[Frame<'_>],
mut metavar_span: Span,
orig_tt: &TokenTree,
marker: &mut Marker,
) -> TokenTree {
let undelimited_seq = matches!(
stack.last(),
Some(Frame {
tts: [_],
kind: FrameKind::Sequence {
sep: None,
kleene_op: KleeneOp::ZeroOrMore | KleeneOp::OneOrMore,
..
},
..
})
);
if undelimited_seq {
// Do not record metavar spans for tokens from undelimited sequences, for perf reasons.
return orig_tt.clone();
}
let insert = |mspans: &mut FxHashMap<_, _>, s, ms| match mspans.try_insert(s, ms) {
Ok(_) => true,
Err(err) => *err.entry.get() == ms, // Tried to insert the same span, still success
};
marker.visit_span(&mut metavar_span);
let no_collision = match orig_tt {
TokenTree::Token(token, ..) => {
with_metavar_spans(|mspans| insert(mspans, token.span, metavar_span))
}
TokenTree::Delimited(dspan, ..) => with_metavar_spans(|mspans| {
insert(mspans, dspan.open, metavar_span)
&& insert(mspans, dspan.close, metavar_span)
&& insert(mspans, dspan.entire(), metavar_span)
}),
};
if no_collision || psess.source_map().is_imported(metavar_span) {
return orig_tt.clone();
}
// Setting metavar spans for the heuristic spans gives better opportunities for combining them
// with neighboring spans even despite their different syntactic contexts.
match orig_tt {
TokenTree::Token(Token { kind, span }, spacing) => {
let span = metavar_span.with_ctxt(span.ctxt());
with_metavar_spans(|mspans| insert(mspans, span, metavar_span));
TokenTree::Token(Token { kind: kind.clone(), span }, *spacing)
}
TokenTree::Delimited(dspan, dspacing, delimiter, tts) => {
let open = metavar_span.with_ctxt(dspan.open.ctxt());
let close = metavar_span.with_ctxt(dspan.close.ctxt());
with_metavar_spans(|mspans| {
insert(mspans, open, metavar_span) && insert(mspans, close, metavar_span)
});
let dspan = DelimSpan::from_pair(open, close);
TokenTree::Delimited(dspan, *dspacing, *delimiter, tts.clone())
}
}
}
/// 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 {
MatchedSingle(_) => 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 $y)+*);+` -- we need to make sure that `x` and `y` repeat the same amount as
/// each other at the given depth when the macro was invoked. If they don't it might mean they were
/// declared at depths which weren't equal or there was a compiler bug. For example, if we have 3 repetitions of
/// the outer sequence and 4 repetitions of the inner sequence for `x`, we should have the same for
/// `y`; otherwise, we can't transcribe them both at the given depth.
fn lockstep_iter_size(
tree: &mbe::TokenTree,
interpolations: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
repeats: &[(usize, usize)],
) -> LockstepIterSize {
use mbe::TokenTree;
match tree {
TokenTree::Delimited(.., delimited) => {
delimited.tts.iter().fold(LockstepIterSize::Unconstrained, |size, tt| {
size.with(lockstep_iter_size(tt, interpolations, repeats))
})
}
TokenTree::Sequence(_, seq) => {
seq.tts.iter().fold(LockstepIterSize::Unconstrained, |size, tt| {
size.with(lockstep_iter_size(tt, interpolations, repeats))
})
}
TokenTree::MetaVar(_, name) | TokenTree::MetaVarDecl(_, name, _) => {
let name = MacroRulesNormalizedIdent::new(*name);
match lookup_cur_matched(name, interpolations, repeats) {
Some(matched) => match matched {
MatchedSingle(_) => LockstepIterSize::Unconstrained,
MatchedSeq(ads) => LockstepIterSize::Constraint(ads.len(), name),
},
_ => LockstepIterSize::Unconstrained,
}
}
TokenTree::MetaVarExpr(_, expr) => {
expr.for_each_metavar(LockstepIterSize::Unconstrained, |lis, ident| {
lis.with(lockstep_iter_size(
&TokenTree::MetaVar(ident.span, *ident),
interpolations,
repeats,
))
})
}
TokenTree::Token(..) => LockstepIterSize::Unconstrained,
}
}
/// Used solely by the `count` meta-variable expression, counts the outer-most repetitions at a
/// given optional nested depth.
///
/// For example, a macro parameter of `$( { $( $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>(
dcx: DiagCtxtHandle<'a>,
depth_user: 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>(depth_curr: usize, depth_max: usize, matched: &NamedMatch) -> PResult<'a, usize> {
match matched {
MatchedSingle(_) => Ok(1),
MatchedSeq(named_matches) => {
if depth_curr == depth_max {
Ok(named_matches.len())
} else {
named_matches.iter().map(|elem| count(depth_curr + 1, depth_max, elem)).sum()
}
}
}
}
/// Maximum depth
fn depth(counter: usize, matched: &NamedMatch) -> usize {
match matched {
MatchedSingle(_) => counter,
MatchedSeq(named_matches) => {
let rslt = counter + 1;
if let Some(elem) = named_matches.first() { depth(rslt, elem) } else { rslt }
}
}
}
let depth_max = depth(0, matched)
.checked_sub(1)
.and_then(|el| el.checked_sub(repeats.len()))
.unwrap_or_default();
if depth_user > depth_max {
return Err(out_of_bounds_err(dcx, depth_max + 1, sp.entire(), "count"));
}
// `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];
}
}
if let MatchedSingle(_) = matched {
return Err(dcx.create_err(CountRepetitionMisplaced { span: sp.entire() }));
}
count(depth_user, depth_max, matched)
}
/// Returns a `NamedMatch` item declared on the LHS given an arbitrary [Ident]
fn matched_from_ident<'ctx, 'interp, 'rslt>(
dcx: DiagCtxtHandle<'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(|| dcx.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>(dcx: DiagCtxtHandle<'a>, max: usize, span: Span, ty: &str) -> Diag<'a> {
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 of meta-variable expression `{ty}` \
must be less than {max}"
)
};
dcx.struct_span_err(span, msg)
}
fn transcribe_metavar_expr<'a>(
dcx: DiagCtxtHandle<'a>,
expr: &MetaVarExpr,
interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
marker: &mut Marker,
repeats: &[(usize, usize)],
result: &mut Vec<TokenTree>,
sp: &DelimSpan,
symbol_gallery: &SymbolGallery,
) -> PResult<'a, ()> {
let mut visited_span = || {
let mut span = sp.entire();
marker.visit_span(&mut span);
span
};
match *expr {
MetaVarExpr::Concat(ref elements) => {
let mut concatenated = String::new();
for element in elements.into_iter() {
let symbol = match element {
MetaVarExprConcatElem::Ident(elem) => elem.name,
MetaVarExprConcatElem::Literal(elem) => *elem,
MetaVarExprConcatElem::Var(ident) => {
match matched_from_ident(dcx, *ident, interp)? {
NamedMatch::MatchedSeq(named_matches) => {
let curr_idx = repeats.last().unwrap().0;
match &named_matches[curr_idx] {
// FIXME(c410-f3r) Nested repetitions are unimplemented
MatchedSeq(_) => unimplemented!(),
MatchedSingle(pnr) => {
extract_symbol_from_pnr(dcx, pnr, ident.span)?
}
}
}
NamedMatch::MatchedSingle(pnr) => {
extract_symbol_from_pnr(dcx, pnr, ident.span)?
}
}
}
};
concatenated.push_str(symbol.as_str());
}
let symbol = nfc_normalize(&concatenated);
let concatenated_span = visited_span();
if !rustc_lexer::is_ident(symbol.as_str()) {
return Err(dcx.struct_span_err(
concatenated_span,
"`${concat(..)}` is not generating a valid identifier",
));
}
symbol_gallery.insert(symbol, concatenated_span);
// The current implementation marks the span as coming from the macro regardless of
// contexts of the concatenated identifiers but this behavior may change in the
// future.
result.push(TokenTree::Token(
Token::from_ast_ident(Ident::new(symbol, concatenated_span)),
Spacing::Alone,
));
}
MetaVarExpr::Count(original_ident, depth) => {
let matched = matched_from_ident(dcx, original_ident, interp)?;
let count = count_repetitions(dcx, depth, 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(dcx, 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(dcx, repeats.len(), sp.entire(), "index")),
},
MetaVarExpr::Len(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(dcx, repeats.len(), sp.entire(), "len")),
},
}
Ok(())
}
/// Extracts an metavariable symbol that can be an identifier, a token tree or a literal.
fn extract_symbol_from_pnr<'a>(
dcx: DiagCtxtHandle<'a>,
pnr: &ParseNtResult,
span_err: Span,
) -> PResult<'a, Symbol> {
match pnr {
ParseNtResult::Ident(nt_ident, is_raw) => {
if let IdentIsRaw::Yes = is_raw {
return Err(dcx.struct_span_err(span_err, RAW_IDENT_ERR));
}
return Ok(nt_ident.name);
}
ParseNtResult::Tt(TokenTree::Token(
Token { kind: TokenKind::Ident(symbol, is_raw), .. },
_,
)) => {
if let IdentIsRaw::Yes = is_raw {
return Err(dcx.struct_span_err(span_err, RAW_IDENT_ERR));
}
return Ok(*symbol);
}
ParseNtResult::Tt(TokenTree::Token(
Token {
kind: TokenKind::Literal(Lit { kind: LitKind::Str, symbol, suffix: None }),
..
},
_,
)) => {
return Ok(*symbol);
}
ParseNtResult::Nt(nt)
if let Nonterminal::NtLiteral(expr) = &**nt
&& let ExprKind::Lit(Lit { kind: LitKind::Str, symbol, suffix: None }) =
&expr.kind =>
{
return Ok(*symbol);
}
_ => Err(dcx
.struct_err(
"metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`",
)
.with_note("currently only string literals are supported")
.with_span(span_err)),
}
}