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mGCA: Enforce WF element types for array valtrees #152492

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Merged
rust-bors merged 3 commits into from
Feb 24, 2026
Merged

mGCA: Enforce WF element types for array valtrees #152492

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1d39a91
require array const params to have correctly typed elems
biscuitrescue Feb 11, 2026
68c705d
tests to check if ValTree checks elems recursively + check array expr…
biscuitrescue Feb 11, 2026
7030be6
move array test to diff file
biscuitrescue Feb 15, 2026
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17 changes: 17 additions & 0 deletions compiler/rustc_trait_selection/src/traits/wf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1094,6 +1094,23 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
},
));
}
ty::Array(elem_ty, _len) => {
let elem_vals = val.to_branch();
let cause = self.cause(ObligationCauseCode::WellFormed(None));

self.out.extend(elem_vals.iter().map(|&elem_val| {
let predicate = ty::PredicateKind::Clause(
ty::ClauseKind::ConstArgHasType(elem_val, *elem_ty),
);
traits::Obligation::with_depth(
tcx,
cause.clone(),
self.recursion_depth,
self.param_env,
predicate,
)
}));
}
_ => {}
}
}
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15 changes: 15 additions & 0 deletions tests/ui/const-generics/array-const-arg-type-mismatch.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
#![feature(adt_const_params, min_generic_const_args)]
//~^ WARN feature `min_generic_const_args` is incomplete
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@asder8215 asder8215 Feb 11, 2026 •
edited
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you can also do #![expect(incomplete_features)] instead of the warning here. I personally would go for that route because I don't think the warning should be mentioned in the .stderr file.

use std::marker::ConstParamTy;

#[derive(Eq, PartialEq, ConstParamTy)]
struct Foo;

struct Bar;

fn test<const N: [Foo; 1]>() {}

fn main() {
test::<{ [Bar] }>();
//~^ ERROR constant `Bar` is not of type `Foo`
}
17 changes: 17 additions & 0 deletions tests/ui/const-generics/array-const-arg-type-mismatch.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/array-const-arg-type-mismatch.rs:1:30
|
LL | #![feature(adt_const_params, min_generic_const_args)]
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
= note: `#[warn(incomplete_features)]` on by default

error: the constant `Bar` is not of type `Foo`
--> $DIR/array-const-arg-type-mismatch.rs:13:14
|
LL | test::<{ [Bar] }>();
| ^^^^^ expected `Foo`, found `Bar`

error: aborting due to 1 previous error; 1 warning emitted

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