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Move Sized check before first error is created

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This commit is contained in:
Michael Goulet 2022-07-01 01:30:48 +00:00
parent 12ab6bfafd
commit 6711313f76
4 changed files with 38 additions and 41 deletions
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62
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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@ -1958,6 +1958,37 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
if predicate.references_error() {
return;
}
// This is kind of a hack: it frequently happens that some earlier
// error prevents types from being fully inferred, and then we get
// a bunch of uninteresting errors saying something like "<generic
// #0> doesn't implement Sized". It may even be true that we
// could just skip over all checks where the self-ty is an
// inference variable, but I was afraid that there might be an
// inference variable created, registered as an obligation, and
// then never forced by writeback, and hence by skipping here we'd
// be ignoring the fact that we don't KNOW the type works
// out. Though even that would probably be harmless, given that
// we're only talking about builtin traits, which are known to be
// inhabited. We used to check for `self.tcx.sess.has_errors()` to
// avoid inundating the user with unnecessary errors, but we now
// check upstream for type errors and don't add the obligations to
// begin with in those cases.
if self.tcx.lang_items().sized_trait() == Some(trait_ref.def_id()) {
if !self.is_tainted_by_errors() {
self.emit_inference_failure_err(
body_id,
span,
trait_ref.self_ty().skip_binder().into(),
vec![],
ErrorCode::E0282,
false,
)
.emit();
}
return;
}
// Typically, this ambiguity should only happen if
// there are unresolved type inference variables
// (otherwise it would suggest a coherence
@ -1997,37 +2028,6 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
)
};
// This is kind of a hack: it frequently happens that some earlier
// error prevents types from being fully inferred, and then we get
// a bunch of uninteresting errors saying something like "<generic
// #0> doesn't implement Sized". It may even be true that we
// could just skip over all checks where the self-ty is an
// inference variable, but I was afraid that there might be an
// inference variable created, registered as an obligation, and
// then never forced by writeback, and hence by skipping here we'd
// be ignoring the fact that we don't KNOW the type works
// out. Though even that would probably be harmless, given that
// we're only talking about builtin traits, which are known to be
// inhabited. We used to check for `self.tcx.sess.has_errors()` to
// avoid inundating the user with unnecessary errors, but we now
// check upstream for type errors and don't add the obligations to
// begin with in those cases.
if self.tcx.lang_items().sized_trait() == Some(trait_ref.def_id()) {
if !self.is_tainted_by_errors() {
self.emit_inference_failure_err(
body_id,
span,
trait_ref.self_ty().skip_binder().into(),
vec![],
ErrorCode::E0282,
false,
)
.emit();
}
err.cancel();
return;
}
let obligation = Obligation::new(
obligation.cause.clone(),
obligation.param_env,