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add note suggesting that predicate is satisfied but is not const

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This commit is contained in:
Michael Goulet 2022-01-26 19:09:44 -08:00
parent 009c1d0248
commit 1ab97dbc52
9 changed files with 71 additions and 0 deletions
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22
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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@ -439,6 +439,28 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
} else {
err.span_label(span, explanation);
}
if trait_predicate.is_const() && obligation.param_env.is_const() {
let non_const_predicate = trait_ref.without_const();
let non_const_obligation = Obligation {
cause: obligation.cause.clone(),
param_env: obligation.param_env.without_const(),
predicate: non_const_predicate.to_predicate(tcx),
recursion_depth: obligation.recursion_depth,
};
if self.predicate_may_hold(&non_const_obligation) {
err.span_note(
span,
&format!(
"the trait `{}` is implemented for `{}`, \
but that implementation is not `const`",
non_const_predicate.print_modifiers_and_trait_path(),
trait_ref.skip_binder().self_ty(),
),
);
}
}
if let Some((msg, span)) = type_def {
err.span_label(span, &msg);
}