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Rollup merge of #120972 - lukas-code:autoderef-type-error, r=compiler-errors

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fix ICE for deref coercions with type errors

Follow-up to https://github.com/rust-lang/rust/pull/120895, where I made types with errors go through the full coercion code, which is necessary if we want to build MIR for bodies with errors (https://github.com/rust-lang/rust/pull/120550).

The code for coercing `&T` to `&U` currently assumes that autoderef for `&T` will succeed for at least two steps (`&T` and `T`):

b17491c8f6/compiler/rustc_hir_typeck/src/coercion.rs (L339-L464)

But for types with errors, we previously only returned the no-op autoderef step (`&{type error}` -> `&{type error}`) and then stopped early. This PR changes autoderef for types with errors to still go through the built-in derefs (e.g. `&&{type error}` -> `&{type error}` -> `{type error}`) and only stop early when it would have to go looking for `Deref` trait impls.

fixes https://github.com/rust-lang/rust/issues/120945

r? ``@compiler-errors`` or compiler
This commit is contained in:
Matthias Krüger 2024-02-12 18:04:11 +01:00 • committed by GitHub
commit 8e5f722ece
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4 changed files with 39 additions and 12 deletions
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8
compiler/rustc_hir_analysis/src/autoderef.rs
View file

@ -91,10 +91,6 @@ impl<'a, 'tcx> Iterator for Autoderef<'a, 'tcx> {
return None;
};
if new_ty.references_error() {
return None;
}
self.state.steps.push((self.state.cur_ty, kind));
debug!(
"autoderef stage #{:?} is {:?} from {:?}",
@ -137,6 +133,10 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
debug!("overloaded_deref_ty({:?})", ty);
let tcx = self.infcx.tcx;
if ty.references_error() {
return None;
}
// <ty as Deref>
let trait_ref = ty::TraitRef::new(tcx, tcx.lang_items().deref_trait()?, [ty]);
let cause = traits::ObligationCause::misc(self.span, self.body_id);

10
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View file

@ -1635,6 +1635,12 @@ fn check_method_receiver<'tcx>(
let receiver_ty = sig.inputs()[0];
let receiver_ty = wfcx.normalize(span, None, receiver_ty);
// If the receiver already has errors reported, consider it valid to avoid
// unnecessary errors (#58712).
if receiver_ty.references_error() {
return Ok(());
}
if tcx.features().arbitrary_self_types {
if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
// Report error; `arbitrary_self_types` was enabled.
@ -1749,9 +1755,7 @@ fn receiver_is_valid<'tcx>(
}
} else {
debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`", receiver_ty, self_ty);
// If the receiver already has errors reported due to it, consider it valid to avoid
// unnecessary errors (#58712).
return receiver_ty.references_error();
return false;
}
}