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Rollup merge of #105345 - yanchen4791:issue-103582-fix, r=jackh726

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Add hint for missing lifetime bound on trait object when type alias is used

Fix issue #103582.

The problem: When a type alias is used to specify the return type of the method in a trait impl, the suggestion for fixing the problem of "missing lifetime bound on trait object" of the trait impl will not be created. The issue caused by the code which searches for the return trait objects when constructing the hint suggestion is not able to find the trait objects since they are specified in the type alias path instead of the return path of the trait impl.

The solution: Trace the trait objects in the type alias path and provide them along with the alias span to generate the suggestion in case the type alias is used in return type of the method in the trait impl.
This commit is contained in:
Matthias Krüger 2023-01-25 22:19:51 +01:00 • committed by GitHub
commit f21728fee4
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6 changed files with 176 additions and 19 deletions
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59
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
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@ -813,17 +813,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
if *outlived_f != ty::ReStatic {
return;
}
let suitable_region = self.infcx.tcx.is_suitable_region(f);
let Some(suitable_region) = suitable_region else { return; };
let fn_returns = self
.infcx
.tcx
.is_suitable_region(f)
.map(|r| self.infcx.tcx.return_type_impl_or_dyn_traits(r.def_id))
.unwrap_or_default();
if fn_returns.is_empty() {
return;
}
let fn_returns = self.infcx.tcx.return_type_impl_or_dyn_traits(suitable_region.def_id);
let param = if let Some(param) = find_param_with_region(self.infcx.tcx, f, outlived_f) {
param
@ -839,15 +832,43 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
};
let captures = format!("captures data from {arg}");
return nice_region_error::suggest_new_region_bound(
self.infcx.tcx,
diag,
fn_returns,
lifetime.to_string(),
Some(arg),
captures,
Some((param.param_ty_span, param.param_ty.to_string())),
self.infcx.tcx.is_suitable_region(f).map(|r| r.def_id),
if !fn_returns.is_empty() {
nice_region_error::suggest_new_region_bound(
self.infcx.tcx,
diag,
fn_returns,
lifetime.to_string(),
Some(arg),
captures,
Some((param.param_ty_span, param.param_ty.to_string())),
Some(suitable_region.def_id),
);
return;
}
let Some((alias_tys, alias_span)) = self
.infcx
.tcx
.return_type_impl_or_dyn_traits_with_type_alias(suitable_region.def_id) else { return; };
// in case the return type of the method is a type alias
let mut spans_suggs: Vec<_> = Vec::new();
for alias_ty in alias_tys {
if alias_ty.span.desugaring_kind().is_some() {
// Skip `async` desugaring `impl Future`.
()
}
if let TyKind::TraitObject(_, lt, _) = alias_ty.kind {
spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
}
}
spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string()));
diag.multipart_suggestion_verbose(
&format!(
"to declare that the trait object {captures}, you can add a lifetime parameter `'a` in the type alias"
),
spans_suggs,
Applicability::MaybeIncorrect,
);
}
}