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On borrow return type, suggest borrowing from arg or owned return type #117914

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Merged
merged 9 commits into from
Dec 12, 2023
Merged

On borrow return type, suggest borrowing from arg or owned return type #117914

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b7a23bc
On borrow return type, suggest borrowing from arg or owned return type
estebank Nov 14, 2023
5fce361
Account for impl Trait in lifetime suggestion
estebank Nov 14, 2023
d30252e
Tweak wording
estebank Nov 14, 2023
dec7f00
Fix incorrect lifetime suggestion
estebank Nov 15, 2023
2a92d82
Suggest 'a when trait object assoc type has '_
estebank Nov 15, 2023
85f26ad
Account for '_ in lifetime suggestion
estebank Nov 15, 2023
bb9d720
Do not consider traits as ownable in suggestion
estebank Nov 15, 2023
02bea16
Rely in resolve and not on path name for `&str` -> `String` suggestion
estebank Nov 15, 2023
eee4cc6
let-chain fmt
estebank Nov 16, 2023
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77 changes: 72 additions & 5 deletions compiler/rustc_resolve/src/late/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2988,6 +2988,9 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
} else if let TyKind::CVarArgs = param.ty.kind {
// Don't suggest `&...` for ffi fn with varargs
None
} else if let TyKind::ImplTrait(..) = &param.ty.kind {
// We handle these in the next `else if` branch.
None
} else {
Some((param.ty.span.shrink_to_lo(), "&".to_string()))
}
Expand All @@ -3010,6 +3013,64 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
Applicability::MaybeIncorrect,
);
"...or alternatively,"
} else if let Some((kind, _span)) =
self.diagnostic_metadata.current_function
&& let FnKind::Fn(_, _, sig, _, _, _) = kind
&& let ast::FnRetTy::Ty(ret_ty) = &sig.decl.output
&& !sig.decl.inputs.is_empty()
&& let arg_refs = sig
.decl
.inputs
.iter()
.filter_map(|param| match &param.ty.kind {
TyKind::ImplTrait(_, bounds) => Some(bounds),
_ => None,
})
.flat_map(|bounds| bounds.into_iter())
.collect::<Vec<_>>()
&& !arg_refs.is_empty()
{
// We have a situation like
// fn g(mut x: impl Iterator<Item = &()>) -> Option<&()>
// So we look at every ref in the trait bound. If there's any, we
// suggest
// fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'a ()>
let mut lt_finder = LifetimeFinder {
lifetime: lt.span,
found: None,
seen: vec![],
};
for bound in arg_refs {
if let ast::GenericBound::Trait(trait_ref, _) = bound {
lt_finder.visit_trait_ref(&trait_ref.trait_ref);
}
}
lt_finder.visit_ty(ret_ty);
let spans_suggs: Vec<_> = lt_finder.seen.iter().filter_map(|ty| {
match &ty.kind {
TyKind::Ref(_, mut_ty) => {
let span = ty.span.with_hi(mut_ty.ty.span.lo());
Some((span, "&'a ".to_string()))
}
_ => None
}
}).collect();
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg| {
info!(?span, ?message, ?intro_sugg);
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.iter().cloned())
.collect(),
Applicability::MaybeIncorrect,
);
higher_ranked
},
);
"...or alternatively,"
} else {
"instead, you are more likely"
};
Expand All @@ -3019,7 +3080,11 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
&& let FnKind::Fn(_, _, sig, _, _, _) = kind
&& let ast::FnRetTy::Ty(ty) = &sig.decl.output
{
let mut lt_finder = LifetimeFinder { lifetime: lt.span, found: None };
let mut lt_finder = LifetimeFinder {
lifetime: lt.span,
found: None,
seen: vec![],
};
lt_finder.visit_ty(&ty);

if let Some(ty) = lt_finder.found {
Expand Down Expand Up @@ -3155,14 +3220,16 @@ pub(super) fn signal_lifetime_shadowing(sess: &Session, orig: Ident, shadower: I
struct LifetimeFinder<'ast> {
lifetime: Span,
found: Option<&'ast Ty>,
seen: Vec<&'ast Ty>,
}

impl<'ast> Visitor<'ast> for LifetimeFinder<'ast> {
fn visit_ty(&mut self, t: &'ast Ty) {
if t.span.lo() == self.lifetime.lo()
&& let TyKind::Ref(_, mut_ty) = &t.kind
{
self.found = Some(&mut_ty.ty);
if let TyKind::Ref(_, mut_ty) = &t.kind {
self.seen.push(t);
if t.span.lo() == self.lifetime.lo() {
self.found = Some(&mut_ty.ty);
}
}
walk_ty(self, t)
}
Expand Down
24 changes: 12 additions & 12 deletions tests/ui/suggestions/impl-trait-missing-lifetime-gated.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,10 @@ help: consider using the `'static` lifetime, but this is uncommon unless you're
|
LL | fn g(mut x: impl Iterator<Item = &()>) -> Option<&'static ()> { x.next() }
| +++++++
help: instead, you are more likely to want to change the argument to be borrowed...
help: consider introducing a named lifetime parameter
|
LL | fn g(mut x: &impl Iterator<Item = &()>) -> Option<&()> { x.next() }
| +
LL | fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'a ()> { x.next() }
| ++++ ~~~ ~~~
help: ...or alternatively, to want to return an owned value
|
LL - fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
Expand All @@ -30,10 +30,10 @@ help: consider using the `'static` lifetime, but this is uncommon unless you're
|
LL | async fn i(mut x: impl Iterator<Item = &()>) -> Option<&'static ()> { x.next() }
| +++++++
help: instead, you are more likely to want to change the argument to be borrowed...
help: consider introducing a named lifetime parameter
|
LL | async fn i(mut x: &impl Iterator<Item = &()>) -> Option<&()> { x.next() }
| +
LL | async fn i<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'a ()> { x.next() }
| ++++ ~~~ ~~~
help: ...or alternatively, to want to return an owned value
|
LL - async fn i(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
Expand Down Expand Up @@ -75,10 +75,10 @@ help: consider using the `'static` lifetime, but this is uncommon unless you're
|
LL | fn g(mut x: impl Foo) -> Option<&'static ()> { x.next() }
| +++++++
help: instead, you are more likely to want to change the argument to be borrowed...
help: consider introducing a named lifetime parameter
|
LL | fn g(mut x: &impl Foo) -> Option<&()> { x.next() }
| +
LL | fn g<'a>(mut x: impl Foo) -> Option<&'a ()> { x.next() }
| ++++ ~~~
help: ...or alternatively, to want to return an owned value
|
LL - fn g(mut x: impl Foo) -> Option<&()> { x.next() }
Expand All @@ -96,10 +96,10 @@ help: consider using the `'static` lifetime, but this is uncommon unless you're
|
LL | fn g(mut x: impl Foo<()>) -> Option<&'static ()> { x.next() }
| +++++++
help: instead, you are more likely to want to change the argument to be borrowed...
help: consider introducing a named lifetime parameter
|
LL | fn g(mut x: &impl Foo<()>) -> Option<&()> { x.next() }
| +
LL | fn g<'a>(mut x: impl Foo<()>) -> Option<&'a ()> { x.next() }
| ++++ ~~~
help: ...or alternatively, to want to return an owned value
|
LL - fn g(mut x: impl Foo<()>) -> Option<&()> { x.next() }
Expand Down