bjoernager/rust
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Point out the actual mismatch error

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This commit is contained in:
Michael Goulet 2023-09-10 03:33:07 +00:00
parent 8be12f4ed7
commit 07851679cd
21 changed files with 52 additions and 1 deletions
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15
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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@ -1,3 +1,5 @@
// ignore-tidy-filelength :(
mod ambiguity;
pub mod on_unimplemented;
pub mod suggestions;
@ -1943,6 +1945,8 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
other: bool,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
// If we have a single implementation, try to unify it with the trait ref
// that failed. This should uncover a better hint for what *is* implemented.
if let [single] = &impl_candidates {
if self.probe(|_| {
let ocx = ObligationCtxt::new(self);
@ -1972,7 +1976,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
std::iter::zip(obligation_trait_ref.args, impl_trait_ref.args)
{
if let Err(terr) =
ocx.eq(&ObligationCause::dummy(), param_env, obligation_arg, impl_arg)
ocx.eq(&ObligationCause::dummy(), param_env, impl_arg, obligation_arg)
{
terrs.push(terr);
}
@ -2000,6 +2004,15 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
(cand.self_ty().to_string(), Style::Highlight),
("`".to_string(), Style::NoStyle),
]);
if let [TypeError::Sorts(exp_found)] = &terrs[..] {
let exp_found = self.resolve_vars_if_possible(*exp_found);
err.help(format!(
"for that trait implementation, expected `{}`, found `{}`",
exp_found.expected, exp_found.found
));
}
true
}) {
return true;