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Suggest assoc ty bound on lifetime in eq constraint
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fmease committed Mar 7, 2024
1 parent 7a08447 commit 6fa9f51
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Showing 5 changed files with 49 additions and 21 deletions.
10 changes: 6 additions & 4 deletions compiler/rustc_parse/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -14,10 +14,6 @@ parse_array_index_offset_of = array indexing not supported in offset_of
parse_assignment_else_not_allowed = <assignment> ... else {"{"} ... {"}"} is not allowed
parse_assoc_lifetime = associated lifetimes are not supported
.label = the lifetime is given here
.help = if you meant to specify a trait object, write `dyn Trait + 'lifetime`
parse_associated_static_item_not_allowed = associated `static` items are not allowed
parse_async_block_in_2015 = `async` blocks are only allowed in Rust 2018 or later
Expand Down Expand Up @@ -450,6 +446,12 @@ parse_lifetime_in_borrow_expression = borrow expressions cannot be annotated wit
.suggestion = remove the lifetime annotation
.label = annotated with lifetime here
parse_lifetime_in_eq_constraint = lifetimes are not permitted in this context
.label = lifetime is not allowed here
.context_label = this introduces an associated item binding
.help = if you meant to specify a trait object, write `dyn /*Trait*/ + {$lifetime}`
.colon_sugg = you might have meant to write a bound here
parse_lone_slash = invalid trailing slash in literal
.label = {parse_lone_slash}
Expand Down
17 changes: 13 additions & 4 deletions compiler/rustc_parse/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2618,13 +2618,22 @@ pub(crate) struct GenericsInPath {
}

#[derive(Diagnostic)]
#[diag(parse_assoc_lifetime)]
#[diag(parse_lifetime_in_eq_constraint)]
#[help]
pub(crate) struct AssocLifetime {
pub(crate) struct LifetimeInEqConstraint {
#[primary_span]
pub span: Span,
#[label]
pub lifetime: Span,
pub span: Span,
pub lifetime: Ident,
#[label(parse_context_label)]
pub binding_label: Span,
#[suggestion(
parse_colon_sugg,
style = "verbose",
applicability = "maybe-incorrect",
code = ": "
)]
pub colon_sugg: Span,
}

#[derive(Diagnostic)]
Expand Down
24 changes: 18 additions & 6 deletions compiler/rustc_parse/src/parser/path.rs
Original file line number Diff line number Diff line change
Expand Up @@ -626,7 +626,11 @@ impl<'a> Parser<'a> {
let bounds = self.parse_generic_bounds()?;
AssocConstraintKind::Bound { bounds }
} else if self.eat(&token::Eq) {
self.parse_assoc_equality_term(ident, self.prev_token.span)?
self.parse_assoc_equality_term(
ident,
gen_args.as_ref(),
self.prev_token.span,
)?
} else {
unreachable!();
};
Expand Down Expand Up @@ -663,11 +667,13 @@ impl<'a> Parser<'a> {
}

/// Parse the term to the right of an associated item equality constraint.
/// That is, parse `<term>` in `Item = <term>`.
/// Right now, this only admits types in `<term>`.
///
/// That is, parse `$term` in `Item = $term` where `$term` is a type or
/// a const expression (wrapped in curly braces if complex).
fn parse_assoc_equality_term(
&mut self,
ident: Ident,
gen_args: Option<&GenericArgs>,
eq: Span,
) -> PResult<'a, AssocConstraintKind> {
let arg = self.parse_generic_arg(None)?;
Expand All @@ -679,9 +685,15 @@ impl<'a> Parser<'a> {
c.into()
}
Some(GenericArg::Lifetime(lt)) => {
let guar =
self.dcx().emit_err(errors::AssocLifetime { span, lifetime: lt.ident.span });
self.mk_ty(span, ast::TyKind::Err(guar)).into()
let guar = self.dcx().emit_err(errors::LifetimeInEqConstraint {
span: lt.ident.span,
lifetime: lt.ident,
binding_label: span,
colon_sugg: gen_args
.map_or(ident.span, |args| args.span())
.between(lt.ident.span),
});
self.mk_ty(lt.ident.span, ast::TyKind::Err(guar)).into()
}
None => {
let after_eq = eq.shrink_to_hi();
Expand Down
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
#[cfg(FALSE)]
fn syntax() {
bar::<Item = 'a>(); //~ ERROR associated lifetimes are not supported
bar::<Item = 'a>(); //~ ERROR lifetimes are not permitted in this context
}

fn main() {}
17 changes: 11 additions & 6 deletions tests/ui/parser/recover/recover-assoc-lifetime-constraint.stderr
Original file line number Diff line number Diff line change
@@ -1,12 +1,17 @@
error: associated lifetimes are not supported
--> $DIR/recover-assoc-lifetime-constraint.rs:3:11
error: lifetimes are not permitted in this context
--> $DIR/recover-assoc-lifetime-constraint.rs:3:18
|
LL | bar::<Item = 'a>();
| ^^^^^^^--
| |
| the lifetime is given here
| -------^^
| | |
| | lifetime is not allowed here
| this introduces an associated item binding
|
= help: if you meant to specify a trait object, write `dyn Trait + 'lifetime`
= help: if you meant to specify a trait object, write `dyn /*Trait*/ + 'a`
help: you might have meant to write a bound here
|
LL | bar::<Item: 'a>();
| ~

error: aborting due to 1 previous error

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