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Rollup merge of #133424 - Nadrieril:guard-patterns-parsing, r=fee1-dead

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Parse guard patterns

This implements the parsing of [RFC3637 Guard Patterns](https://rust-lang.github.io/rfcs/3637-guard-patterns.html) (see also [tracking issue](https://github.com/rust-lang/rust/issues/129967)). This PR is extracted from https://github.com/rust-lang/rust/pull/129996 with minor modifications.

cc `@max-niederman`
This commit is contained in:
Matthias Krüger 2024-12-08 17:18:50 +01:00 • committed by GitHub
commit 1868c8f66f
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GPG key ID: B5690EEEBB952194
31 changed files with 328 additions and 81 deletions
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58
compiler/rustc_parse/src/parser/expr.rs
View file

@ -2631,7 +2631,7 @@ impl<'a> Parser<'a> {
};
self.bump(); // Eat `let` token
let lo = self.prev_token.span;
let pat = self.parse_pat_allow_top_alt(
let pat = self.parse_pat_no_top_guard(
None,
RecoverComma::Yes,
RecoverColon::Yes,
@ -2778,7 +2778,7 @@ impl<'a> Parser<'a> {
};
// Try to parse the pattern `for ($PAT) in $EXPR`.
let pat = match (
self.parse_pat_allow_top_alt(
self.parse_pat_allow_top_guard(
None,
RecoverComma::Yes,
RecoverColon::Yes,
@ -3241,7 +3241,7 @@ impl<'a> Parser<'a> {
// then we should recover.
let mut snapshot = this.create_snapshot_for_diagnostic();
let pattern_follows = snapshot
.parse_pat_allow_top_alt(
.parse_pat_no_top_guard(
None,
RecoverComma::Yes,
RecoverColon::Yes,
@ -3315,43 +3315,37 @@ impl<'a> Parser<'a> {
fn parse_match_arm_pat_and_guard(&mut self) -> PResult<'a, (P<Pat>, Option<P<Expr>>)> {
if self.token == token::OpenDelim(Delimiter::Parenthesis) {
// Detect and recover from `($pat if $cond) => $arm`.
let left = self.token.span;
match self.parse_pat_allow_top_alt(
let pat = self.parse_pat_no_top_guard(
None,
RecoverComma::Yes,
RecoverColon::Yes,
CommaRecoveryMode::EitherTupleOrPipe,
) {
Ok(pat) => Ok((pat, self.parse_match_arm_guard()?)),
Err(err)
if let prev_sp = self.prev_token.span
&& let true = self.eat_keyword(kw::If) =>
{
// We know for certain we've found `($pat if` so far.
let mut cond = match self.parse_match_guard_condition() {
Ok(cond) => cond,
Err(cond_err) => {
cond_err.cancel();
return Err(err);
}
};
err.cancel();
CondChecker::new(self).visit_expr(&mut cond);
self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis)]);
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
let right = self.prev_token.span;
self.dcx().emit_err(errors::ParenthesesInMatchPat {
span: vec![left, right],
sugg: errors::ParenthesesInMatchPatSugg { left, right },
});
Ok((self.mk_pat(left.to(prev_sp), ast::PatKind::Wild), Some(cond)))
}
Err(err) => Err(err),
)?;
if let ast::PatKind::Paren(subpat) = &pat.kind
&& let ast::PatKind::Guard(..) = &subpat.kind
{
// Detect and recover from `($pat if $cond) => $arm`.
// FIXME(guard_patterns): convert this to a normal guard instead
let span = pat.span;
let ast::PatKind::Paren(subpat) = pat.into_inner().kind else { unreachable!() };
let ast::PatKind::Guard(_, mut cond) = subpat.into_inner().kind else {
unreachable!()
};
self.psess.gated_spans.ungate_last(sym::guard_patterns, cond.span);
CondChecker::new(self).visit_expr(&mut cond);
let right = self.prev_token.span;
self.dcx().emit_err(errors::ParenthesesInMatchPat {
span: vec![left, right],
sugg: errors::ParenthesesInMatchPatSugg { left, right },
});
Ok((self.mk_pat(span, ast::PatKind::Wild), Some(cond)))
} else {
Ok((pat, self.parse_match_arm_guard()?))
}
} else {
// Regular parser flow:
let pat = self.parse_pat_allow_top_alt(
let pat = self.parse_pat_no_top_guard(
None,
RecoverComma::Yes,
RecoverColon::Yes,