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Rollup merge of #133394 - compiler-errors:dyn-more-errors, r=lcnr

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Bail on more errors in dyn ty lowering

If we have more than one principal trait, or if we have a principal trait with errors in it, then bail with `TyKind::Error` rather than attempting lowering. Lowering a dyn trait with more than one principal just arbitrarily chooses the first one and drops the subsequent ones, and lowering a dyn trait path with errors in it is just kinda useless.

This suppresses unnecessary errors which I think is net-good, but also is important to make sure that we don't end up leaking `{type error}` in https://github.com/rust-lang/rust/issues/133388 error messaging :)

r? types
This commit is contained in:
Michael Goulet 2024-11-26 12:03:44 -05:00 • committed by GitHub
commit b0ed5ac730
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22 changed files with 63 additions and 457 deletions
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20
compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
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@ -8,7 +8,8 @@ use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS;
use rustc_middle::span_bug;
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::{
self, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable, Upcast,
self, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable,
TypeVisitableExt, Upcast,
};
use rustc_span::{ErrorGuaranteed, Span};
use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
@ -92,11 +93,20 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
// We don't support >1 principal
if regular_traits.len() > 1 {
let _ = self.report_trait_object_addition_traits_error(&regular_traits);
} else if regular_traits.is_empty() && auto_traits.is_empty() {
let reported = self.report_trait_object_with_no_traits_error(span, &trait_bounds);
return Ty::new_error(tcx, reported);
let guar = self.report_trait_object_addition_traits_error(&regular_traits);
return Ty::new_error(tcx, guar);
}
// We don't support empty trait objects.
if regular_traits.is_empty() && auto_traits.is_empty() {
let guar = self.report_trait_object_with_no_traits_error(span, &trait_bounds);
return Ty::new_error(tcx, guar);
}
// Don't create a dyn trait if we have errors in the principal.
if let Err(guar) = trait_bounds.error_reported() {
return Ty::new_error(tcx, guar);
}
// Check that there are no gross dyn-compatibility violations;