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Warn for outlives lint when gats are enabled for non-gats #91853

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Warn for outlives lint when gats are enabled for non-gats #91853

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c018ead
Warn when gats are enabled and we trigger the outlives lint
jackh726 Dec 13, 2021
cc51c4e
Change to error for crater
jackh726 Feb 7, 2022
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21 changes: 9 additions & 12 deletions compiler/rustc_typeck/src/check/wfcheck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -285,11 +285,6 @@ fn check_gat_where_clauses(
return;
}
let generics: &ty::Generics = tcx.generics_of(trait_item.def_id);
// If the current associated type doesn't have any (own) params, it's not a GAT
// FIXME(jackh726): we can also warn in the more general case
if generics.params.len() == 0 {
return;
}
let associated_items: &ty::AssocItems<'_> = tcx.associated_items(encl_trait_def_id);
let mut clauses: Option<FxHashSet<ty::Predicate<'_>>> = None;
// For every function in this trait...
Expand Down Expand Up @@ -465,10 +460,12 @@ fn check_gat_where_clauses(

if !clauses.is_empty() {
let plural = if clauses.len() > 1 { "s" } else { "" };
let mut err = tcx.sess.struct_span_err(
trait_item.span,
&format!("missing required bound{} on `{}`", plural, trait_item.ident),
);
let severity = if generics.params.len() == 0 { "recommended" } else { "required" };
let mut err =
tcx.sess.struct_span_err(
trait_item.span,
&format!("missing {} bound{} on `{}`", severity, plural, trait_item.ident),
);

let suggestion = format!(
"{} {}",
Expand All @@ -481,15 +478,15 @@ fn check_gat_where_clauses(
);
err.span_suggestion(
trait_item.generics.where_clause.tail_span_for_suggestion(),
&format!("add the required where clause{}", plural),
&format!("add the {} where clause{}", severity, plural),
suggestion,
Applicability::MachineApplicable,
);

let bound = if clauses.len() > 1 { "these bounds are" } else { "this bound is" };
err.note(&format!(
"{} currently required to ensure that impls have maximum flexibility",
bound
"{} currently {} to ensure that impls have maximum flexibility",
bound, severity,
));
err.note(
"we are soliciting feedback, see issue #87479 \
Expand Down
14 changes: 12 additions & 2 deletions src/test/ui/generic-associated-types/self-outlives-lint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -102,12 +102,22 @@ impl Des3 for () {
}
*/

// Similar case to before, except with GAT.
// Similar case to before, except without GAT.
trait NoGat<'a> {
type Bar;
//~^ missing recommended
fn method(&'a self) -> Self::Bar;
}


// Same as above, except explicit
trait NoGatWarning<'a> {
type Output;
//~^ missing recommended

fn method(&'a self) -> <Self as NoGatWarning<'a>>::Output;
}

// Lifetime is not on function; except `Self: 'a`
// FIXME: we require two bounds (`where Self: 'a, Self: 'b`) when we should only require one
trait TraitLifetime<'a> {
Expand Down Expand Up @@ -184,7 +194,7 @@ trait MultipleMethods {

// We would normally require `Self: 'a`, but we can prove that `Self: 'static`
// because of the the bounds on the trait, so the bound is proven
trait Trait: 'static {
trait StaticTrait: 'static {
type Assoc<'a>;
fn make_assoc(_: &u32) -> Self::Assoc<'_>;
}
Expand Down
36 changes: 29 additions & 7 deletions src/test/ui/generic-associated-types/self-outlives-lint.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -75,8 +75,30 @@ LL | type Out<'x, D>;
= note: this bound is currently required to ensure that impls have maximum flexibility
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

warning: missing recommended bound on `Bar`
--> $DIR/self-outlives-lint.rs:107:5
|
LL | type Bar;
| ^^^^^^^^-
| |
| help: add the recommended where clause: `where Self: 'a`
|
= note: this bound is currently recommended to ensure that impls have maximum flexibility
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

warning: missing recommended bound on `Output`
--> $DIR/self-outlives-lint.rs:115:5
|
LL | type Output;
| ^^^^^^^^^^^-
| |
| help: add the recommended where clause: `where Self: 'a`
|
= note: this bound is currently recommended to ensure that impls have maximum flexibility
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bounds on `Bar`
--> $DIR/self-outlives-lint.rs:114:5
--> $DIR/self-outlives-lint.rs:124:5
|
LL | type Bar<'b>;
| ^^^^^^^^^^^^-
Expand All @@ -87,7 +109,7 @@ LL | type Bar<'b>;
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bound on `Bar`
--> $DIR/self-outlives-lint.rs:122:5
--> $DIR/self-outlives-lint.rs:132:5
|
LL | type Bar<'b>;
| ^^^^^^^^^^^^-
Expand All @@ -98,7 +120,7 @@ LL | type Bar<'b>;
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bound on `Bar`
--> $DIR/self-outlives-lint.rs:129:5
--> $DIR/self-outlives-lint.rs:139:5
|
LL | type Bar<'b>;
| ^^^^^^^^^^^^-
Expand All @@ -109,7 +131,7 @@ LL | type Bar<'b>;
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bound on `Iterator`
--> $DIR/self-outlives-lint.rs:143:5
--> $DIR/self-outlives-lint.rs:153:5
|
LL | type Iterator<'a>: Iterator<Item = Self::Item<'a>>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-
Expand All @@ -120,7 +142,7 @@ LL | type Iterator<'a>: Iterator<Item = Self::Item<'a>>;
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bound on `Bar`
--> $DIR/self-outlives-lint.rs:151:5
--> $DIR/self-outlives-lint.rs:161:5
|
LL | type Bar<'a, 'b>;
| ^^^^^^^^^^^^^^^^-
Expand All @@ -131,7 +153,7 @@ LL | type Bar<'a, 'b>;
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: missing required bound on `Fut`
--> $DIR/self-outlives-lint.rs:167:5
--> $DIR/self-outlives-lint.rs:177:5
|
LL | type Fut<'out>;
| ^^^^^^^^^^^^^^-
Expand All @@ -141,5 +163,5 @@ LL | type Fut<'out>;
= note: this bound is currently required to ensure that impls have maximum flexibility
= note: we are soliciting feedback, see issue #87479 <https://github.com/rust-lang/rust/issues/87479> for more information

error: aborting due to 13 previous errors
error: aborting due to 13 previous errors; 2 warnings emitted