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Handle infer vars in anon consts on stable

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Boxy 2024-11-12 21:35:38 +00:00
parent 6503543d11
commit 6dad074907
4 changed files with 76 additions and 9 deletions
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30
compiler/rustc_trait_selection/src/traits/mod.rs
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@ -578,16 +578,28 @@ pub fn try_evaluate_const<'tcx>(
(args, param_env)
}
}
} else {
// FIXME: We don't check anything on stable as the only way we can wind up with
// an unevaluated constant containing generic parameters is through array repeat
// expression counts which have a future compat lint for usage of generic parameters
// instead of a hard error.
} else if tcx.def_kind(uv.def) == DefKind::AnonConst && uv.has_non_region_infer() {
// FIXME: remove this when `const_evaluatable_unchecked` is a hard error.
//
// This codepath is however also reachable by `generic_const_exprs` and some other
// feature gates which allow constants in the type system to use generic parameters.
// In theory we should be checking for generic parameters here and returning an error
// in such cases.
// Diagnostics will sometimes replace the identity args of anon consts in
// array repeat expr counts with inference variables so we have to handle this
// even though it is not something we should ever actually encounter.
//
// Array repeat expr counts are allowed to syntactically use generic parameters
// but must not actually depend on them in order to evalaute succesfully. This means
// that it is actually fine to evalaute them in their own environment rather than with
// the actually provided generic arguments.
tcx.dcx().delayed_bug(
"Encountered anon const with inference variable args but no error reported",
);
let args = GenericArgs::identity_for_item(tcx, uv.def);
let param_env = tcx.param_env(uv.def);
(args, param_env)
} else {
// FIXME: This codepath is reachable under `associated_const_equality` and in the
// future will be reachable by `min_generic_const_args`. We should handle inference
// variables and generic parameters properly instead of doing nothing.
(uv.args, param_env)
};
let uv = ty::UnevaluatedConst::new(uv.def, args);