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Clean up parsers related to generic bounds

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This commit is contained in:
León Orell Valerian Liehr
2025-08-15 23:01:32 +02:00
parent eb3e0d4c8a
commit f8f7c27d4f
8 changed files with 86 additions and 104 deletions
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4
compiler/rustc_parse/src/parser/expr.rs
View File

@@ -2397,12 +2397,12 @@ impl<'a> Parser<'a> {
let before = self.prev_token;
let binder = if self.check_keyword(exp!(For)) {
let lo = self.token.span;
let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
let (bound_vars, _) = self.parse_higher_ranked_binder()?;
let span = lo.to(self.prev_token.span);
self.psess.gated_spans.gate(sym::closure_lifetime_binder, span);
ClosureBinder::For { span, generic_params: lifetime_defs }
ClosureBinder::For { span, generic_params: bound_vars }
} else {
ClosureBinder::NotPresent
};

11
compiler/rustc_parse/src/parser/generics.rs
View File

@@ -172,8 +172,11 @@ impl<'a> Parser<'a> {
})
}
/// Parses a (possibly empty) list of lifetime and type parameters, possibly including
/// a trailing comma and erroneous trailing attributes.
/// Parse a (possibly empty) list of generic (lifetime, type, const) parameters.
///
/// ```ebnf
/// GenericParams = (GenericParam ("," GenericParam)* ","?)?
/// ```
pub(super) fn parse_generic_params(&mut self) -> PResult<'a, ThinVec<ast::GenericParam>> {
let mut params = ThinVec::new();
let mut done = false;
@@ -520,7 +523,7 @@ impl<'a> Parser<'a> {
// * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
// * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
// * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
let (bound_vars, _) = self.parse_higher_ranked_binder()?;
// Parse type with mandatory colon and (possibly empty) bounds,
// or with mandatory equality sign and the second type.
@@ -528,7 +531,7 @@ impl<'a> Parser<'a> {
if self.eat(exp!(Colon)) {
let bounds = self.parse_generic_bounds()?;
Ok(ast::WherePredicateKind::BoundPredicate(ast::WhereBoundPredicate {
bound_generic_params: lifetime_defs,
bound_generic_params: bound_vars,
bounded_ty: ty,
bounds,
}))

139
compiler/rustc_parse/src/parser/ty.rs
View File

@@ -307,11 +307,11 @@ impl<'a> Parser<'a> {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
let (bound_vars, _) = self.parse_higher_ranked_binder()?;
if self.check_fn_front_matter(false, Case::Sensitive) {
self.parse_ty_fn_ptr(
lo,
lifetime_defs,
bound_vars,
Some(self.prev_token.span.shrink_to_lo()),
recover_return_sign,
)?
@@ -325,7 +325,7 @@ impl<'a> Parser<'a> {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
let kind = self.parse_remaining_bounds_path(
lifetime_defs,
bound_vars,
path,
lo,
parse_plus,
@@ -358,7 +358,7 @@ impl<'a> Parser<'a> {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
self.parse_remaining_bounds_path(
lifetime_defs,
bound_vars,
path,
lo,
parse_plus,
@@ -442,7 +442,7 @@ impl<'a> Parser<'a> {
let ty = ts.into_iter().next().unwrap();
let maybe_bounds = allow_plus == AllowPlus::Yes && self.token.is_like_plus();
match ty.kind {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
// `"(" BareTraitBound ")" "+" Bound "+" ...`.
TyKind::Path(None, path) if maybe_bounds => self.parse_remaining_bounds_path(
ThinVec::new(),
path,
@@ -847,11 +847,13 @@ impl<'a> Parser<'a> {
Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
}
fn parse_precise_capturing_args(
&mut self,
lo: Span,
parens: ast::Parens,
) -> PResult<'a, GenericBound> {
/// Parse a use-bound aka precise capturing list.
///
/// ```ebnf
/// UseBound = "use" "<" (PreciseCapture ("," PreciseCapture)* ","?)? ">"
/// PreciseCapture = "Self" | Ident | Lifetime
/// ```
fn parse_use_bound(&mut self, lo: Span, parens: ast::Parens) -> PResult<'a, GenericBound> {
self.expect_lt()?;
let (args, _, _) = self.parse_seq_to_before_tokens(
&[exp!(Gt)],
@@ -880,16 +882,7 @@ impl<'a> Parser<'a> {
if let ast::Parens::Yes = parens {
self.expect(exp!(CloseParen))?;
let hi = self.prev_token.span;
let mut diag = self
.dcx()
.struct_span_err(lo.to(hi), "precise capturing lists may not be parenthesized");
diag.multipart_suggestion(
"remove the parentheses",
vec![(lo, String::new()), (hi, String::new())],
Applicability::MachineApplicable,
);
diag.emit();
self.report_parenthesized_bound(lo, self.prev_token.span, "precise capturing lists");
}
Ok(GenericBound::Use(args, lo.to(self.prev_token.span)))
@@ -950,9 +943,10 @@ impl<'a> Parser<'a> {
self.parse_generic_bounds_common(AllowPlus::Yes)
}
/// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
/// Parse generic bounds.
///
/// See `parse_generic_bound` for the `BOUND` grammar.
/// Only if `allow_plus` this parses a `+`-separated list of bounds (trailing `+` is admitted).
/// Otherwise, this only parses a single bound or none.
fn parse_generic_bounds_common(&mut self, allow_plus: AllowPlus) -> PResult<'a, GenericBounds> {
let mut bounds = Vec::new();
@@ -998,42 +992,56 @@ impl<'a> Parser<'a> {
|| self.check_keyword(exp!(Use))
}
/// Parses a bound according to the grammar:
/// Parse a bound.
///
/// ```ebnf
/// BOUND = TY_BOUND | LT_BOUND
/// Bound = LifetimeBound | UseBound | TraitBound
/// ```
fn parse_generic_bound(&mut self) -> PResult<'a, GenericBound> {
let leading_token = self.prev_token;
let lo = self.token.span;
// We only admit parenthesized *trait* bounds. However, we want to gracefully recover from
// other kinds of parenthesized bounds, so parse the opening parenthesis *here*.
//
// In the future we might want to lift this syntactic restriction and
// introduce "`GenericBound::Paren(Box<GenericBound>)`".
let parens = if self.eat(exp!(OpenParen)) { ast::Parens::Yes } else { ast::Parens::No };
if self.token.is_lifetime() {
self.parse_generic_lt_bound(lo, parens)
self.parse_lifetime_bound(lo, parens)
} else if self.eat_keyword(exp!(Use)) {
self.parse_precise_capturing_args(lo, parens)
self.parse_use_bound(lo, parens)
} else {
self.parse_generic_ty_bound(lo, parens, &leading_token)
self.parse_trait_bound(lo, parens, &leading_token)
}
}
/// Parses a lifetime ("outlives") bound, e.g. `'a`, according to:
/// Parse a lifetime-bound aka outlives-bound.
///
/// ```ebnf
/// LT_BOUND = LIFETIME
/// LifetimeBound = Lifetime
/// ```
fn parse_generic_lt_bound(
&mut self,
lo: Span,
parens: ast::Parens,
) -> PResult<'a, GenericBound> {
fn parse_lifetime_bound(&mut self, lo: Span, parens: ast::Parens) -> PResult<'a, GenericBound> {
let lt = self.expect_lifetime();
let bound = GenericBound::Outlives(lt);
if let ast::Parens::Yes = parens {
// FIXME(Centril): Consider not erroring here and accepting `('lt)` instead,
// possibly introducing `GenericBound::Paren(Box<GenericBound>)`?
self.recover_paren_lifetime(lo)?;
self.expect(exp!(CloseParen))?;
self.report_parenthesized_bound(lo, self.prev_token.span, "lifetime bounds");
}
Ok(bound)
Ok(GenericBound::Outlives(lt))
}
fn report_parenthesized_bound(&self, lo: Span, hi: Span, kind: &str) -> ErrorGuaranteed {
let mut diag =
self.dcx().struct_span_err(lo.to(hi), format!("{kind} may not be parenthesized"));
diag.multipart_suggestion(
"remove the parentheses",
vec![(lo, String::new()), (hi, String::new())],
Applicability::MachineApplicable,
);
diag.emit()
}
/// Emits an error if any trait bound modifiers were present.
@@ -1078,27 +1086,17 @@ impl<'a> Parser<'a> {
unreachable!("lifetime bound intercepted in `parse_generic_ty_bound` but no modifiers?")
}
/// Recover on `('lifetime)` with `(` already eaten.
fn recover_paren_lifetime(&mut self, lo: Span) -> PResult<'a, ()> {
self.expect(exp!(CloseParen))?;
let span = lo.to(self.prev_token.span);
let sugg = errors::RemoveParens { lo, hi: self.prev_token.span };
self.dcx().emit_err(errors::ParenthesizedLifetime { span, sugg });
Ok(())
}
/// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `[const] Trait`.
///
/// If no modifiers are present, this does not consume any tokens.
///
/// ```ebnf
/// CONSTNESS = [["["] "const" ["]"]]
/// ASYNCNESS = ["async"]
/// POLARITY = ["?" | "!"]
/// Constness = ("const" | "[" "const" "]")?
/// Asyncness = "async"?
/// Polarity = ("?" | "!")?
/// ```
///
/// See `parse_generic_ty_bound` for the complete grammar of trait bound modifiers.
/// See `parse_trait_bound` for more context.
fn parse_trait_bound_modifiers(&mut self) -> PResult<'a, TraitBoundModifiers> {
let modifier_lo = self.token.span;
let constness = self.parse_bound_constness()?;
@@ -1191,20 +1189,21 @@ impl<'a> Parser<'a> {
})
}
/// Parses a type bound according to:
/// ```ebnf
/// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
/// TY_BOUND_NOPAREN = [for<GENERIC_PARAMS> CONSTNESS ASYNCNESS | POLARITY] SIMPLE_PATH
/// ```
/// Parse a trait bound.
///
/// For example, this grammar accepts `for<'a: 'b> [const] ?m::Trait<'a>`.
fn parse_generic_ty_bound(
/// ```ebnf
/// TraitBound = BareTraitBound | "(" BareTraitBound ")"
/// BareTraitBound =
/// (HigherRankedBinder Constness Asyncness | Polarity)
/// TypePath
/// ```
fn parse_trait_bound(
&mut self,
lo: Span,
parens: ast::Parens,
leading_token: &Token,
) -> PResult<'a, GenericBound> {
let (mut lifetime_defs, binder_span) = self.parse_late_bound_lifetime_defs()?;
let (mut bound_vars, binder_span) = self.parse_higher_ranked_binder()?;
let modifiers_lo = self.token.span;
let modifiers = self.parse_trait_bound_modifiers()?;
@@ -1227,11 +1226,11 @@ impl<'a> Parser<'a> {
// e.g. `T: for<'a> 'a` or `T: [const] 'a`.
if self.token.is_lifetime() {
let _: ErrorGuaranteed = self.error_lt_bound_with_modifiers(modifiers, binder_span);
return self.parse_generic_lt_bound(lo, parens);
return self.parse_lifetime_bound(lo, parens);
}
if let (more_lifetime_defs, Some(binder_span)) = self.parse_late_bound_lifetime_defs()? {
lifetime_defs.extend(more_lifetime_defs);
if let (more_bound_vars, Some(binder_span)) = self.parse_higher_ranked_binder()? {
bound_vars.extend(more_bound_vars);
self.dcx().emit_err(errors::BinderBeforeModifiers { binder_span, modifiers_span });
}
@@ -1291,7 +1290,7 @@ impl<'a> Parser<'a> {
};
if self.may_recover() && self.token == TokenKind::OpenParen {
self.recover_fn_trait_with_lifetime_params(&mut path, &mut lifetime_defs)?;
self.recover_fn_trait_with_lifetime_params(&mut path, &mut bound_vars)?;
}
if let ast::Parens::Yes = parens {
@@ -1314,7 +1313,7 @@ impl<'a> Parser<'a> {
}
let poly_trait =
PolyTraitRef::new(lifetime_defs, path, modifiers, lo.to(self.prev_token.span), parens);
PolyTraitRef::new(bound_vars, path, modifiers, lo.to(self.prev_token.span), parens);
Ok(GenericBound::Trait(poly_trait))
}
@@ -1352,8 +1351,12 @@ impl<'a> Parser<'a> {
}
}
/// Optionally parses `for<$generic_params>`.
pub(super) fn parse_late_bound_lifetime_defs(
/// Parse an optional higher-ranked binder.
///
/// ```ebnf
/// HigherRankedBinder = ("for" "<" GenericParams ">")?
/// ```
pub(super) fn parse_higher_ranked_binder(
&mut self,
) -> PResult<'a, (ThinVec<GenericParam>, Option<Span>)> {
if self.eat_keyword(exp!(For)) {