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Generic associated consts: Check regions earlier when comparing impl with trait item def #123898

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Merged
merged 1 commit into from
Apr 14, 2024
Merged

Generic associated consts: Check regions earlier when comparing impl with trait item def #123898

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6 changes: 2 additions & 4 deletions compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1723,6 +1723,7 @@ pub(super) fn compare_impl_const_raw(

compare_number_of_generics(tcx, impl_const_item, trait_const_item, false)?;
compare_generic_param_kinds(tcx, impl_const_item, trait_const_item, false)?;
check_region_bounds_on_impl_item(tcx, impl_const_item, trait_const_item, false)?;
compare_const_predicate_entailment(tcx, impl_const_item, trait_const_item, impl_trait_ref)
}

Expand Down Expand Up @@ -1763,8 +1764,6 @@ fn compare_const_predicate_entailment<'tcx>(
let impl_ct_predicates = tcx.predicates_of(impl_ct.def_id);
let trait_ct_predicates = tcx.predicates_of(trait_ct.def_id);

check_region_bounds_on_impl_item(tcx, impl_ct, trait_ct, false)?;
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On lifetime param mismatches, we ICE'd in tcx.type_of(trait_ct.def_id).instantiate(tcx, trait_to_impl_args) a few lines further up for obvious reasons. That's on me, I messed that up in the initial GCI PR.


// The predicates declared by the impl definition, the trait and the
// associated const in the trait are assumed.
let impl_predicates = tcx.predicates_of(impl_ct_predicates.parent.unwrap());
Expand Down Expand Up @@ -1866,6 +1865,7 @@ pub(super) fn compare_impl_ty<'tcx>(
let _: Result<(), ErrorGuaranteed> = try {
compare_number_of_generics(tcx, impl_ty, trait_ty, false)?;
compare_generic_param_kinds(tcx, impl_ty, trait_ty, false)?;
check_region_bounds_on_impl_item(tcx, impl_ty, trait_ty, false)?;
compare_type_predicate_entailment(tcx, impl_ty, trait_ty, impl_trait_ref)?;
check_type_bounds(tcx, trait_ty, impl_ty, impl_trait_ref)?;
};
Expand All @@ -1886,8 +1886,6 @@ fn compare_type_predicate_entailment<'tcx>(
let impl_ty_predicates = tcx.predicates_of(impl_ty.def_id);
let trait_ty_predicates = tcx.predicates_of(trait_ty.def_id);

check_region_bounds_on_impl_item(tcx, impl_ty, trait_ty, false)?;
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There was no need to move this one out of compare_type_predicate_entailment except consistency with both compare_{method,const}_predicate_entailment which is reason enough imo.


let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_args);
if impl_ty_own_bounds.len() == 0 {
// Nothing to check.
Expand Down
11 changes: 7 additions & 4 deletions tests/ui/generic-const-items/compare-impl-item.rs
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Expand Up @@ -6,9 +6,10 @@ trait Trait<P> {
const B<const K: u64, const Q: u64>: u64;
const C<T>: T;
const D<const N: usize>: usize;
const E<'a>: &'a ();

const E: usize;
const F<T: PartialEq>: ();
const F: usize;
const G<T: PartialEq>: ();
}

impl<P> Trait<P> for () {
Expand All @@ -20,11 +21,13 @@ impl<P> Trait<P> for () {
//~^ ERROR const `C` has 0 type parameters but its trait declaration has 1 type parameter
const D<const N: u16>: u16 = N;
//~^ ERROR const `D` has an incompatible generic parameter for trait `Trait`
const E: &'static () = &();
//~^ ERROR lifetime parameters or bounds on const `E` do not match the trait declaration

const E: usize = 1024
const F: usize = 1024
where
P: Copy; //~ ERROR impl has stricter requirements than trait
const F<T: Eq>: () = (); //~ ERROR impl has stricter requirements than trait
const G<T: Eq>: () = (); //~ ERROR impl has stricter requirements than trait
}

fn main() {}
35 changes: 22 additions & 13 deletions tests/ui/generic-const-items/compare-impl-item.stderr
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@@ -1,5 +1,5 @@
error[E0049]: const `A` has 1 type parameter but its trait declaration has 0 type parameters
--> $DIR/compare-impl-item.rs:15:13
--> $DIR/compare-impl-item.rs:16:13
|
LL | const A: ();
| - expected 0 type parameters
Expand All @@ -8,7 +8,7 @@ LL | const A<T>: () = ();
| ^ found 1 type parameter

error[E0049]: const `B` has 1 const parameter but its trait declaration has 2 const parameters
--> $DIR/compare-impl-item.rs:17:13
--> $DIR/compare-impl-item.rs:18:13
|
LL | const B<const K: u64, const Q: u64>: u64;
| ------------ ------------
Expand All @@ -19,7 +19,7 @@ LL | const B<const K: u64>: u64 = 0;
| ^^^^^^^^^^^^ found 1 const parameter

error[E0049]: const `C` has 0 type parameters but its trait declaration has 1 type parameter
--> $DIR/compare-impl-item.rs:19:13
--> $DIR/compare-impl-item.rs:20:13
|
LL | const C<T>: T;
| - expected 1 type parameter
Expand All @@ -28,7 +28,7 @@ LL | const C<'a>: &'a str = "";
| ^^ found 0 type parameters

error[E0053]: const `D` has an incompatible generic parameter for trait `Trait`
--> $DIR/compare-impl-item.rs:21:13
--> $DIR/compare-impl-item.rs:22:13
|
LL | trait Trait<P> {
| -----
Expand All @@ -42,25 +42,34 @@ LL | impl<P> Trait<P> for () {
LL | const D<const N: u16>: u16 = N;
| ^^^^^^^^^^^^ found const parameter of type `u16`

error[E0195]: lifetime parameters or bounds on const `E` do not match the trait declaration
--> $DIR/compare-impl-item.rs:24:12
|
LL | const E<'a>: &'a ();
| ---- lifetimes in impl do not match this const in trait
...
LL | const E: &'static () = &();
| ^ lifetimes do not match const in trait

error[E0276]: impl has stricter requirements than trait
--> $DIR/compare-impl-item.rs:26:12
--> $DIR/compare-impl-item.rs:29:12
|
LL | const E: usize;
| -------------- definition of `E` from trait
LL | const F: usize;
| -------------- definition of `F` from trait
...
LL | P: Copy;
| ^^^^ impl has extra requirement `P: Copy`

error[E0276]: impl has stricter requirements than trait
--> $DIR/compare-impl-item.rs:27:16
--> $DIR/compare-impl-item.rs:30:16
|
LL | const F<T: PartialEq>: ();
| ------------------------- definition of `F` from trait
LL | const G<T: PartialEq>: ();
| ------------------------- definition of `G` from trait
...
LL | const F<T: Eq>: () = ();
LL | const G<T: Eq>: () = ();
| ^^ impl has extra requirement `T: Eq`

error: aborting due to 6 previous errors
error: aborting due to 7 previous errors

Some errors have detailed explanations: E0049, E0053, E0276.
Some errors have detailed explanations: E0049, E0053, E0195, E0276.
For more information about an error, try `rustc --explain E0049`.
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