Rollup merge of #135378 - compiler-errors:unnecessary-stashing, r=chenyukang

Remove a bunch of diagnostic stashing that doesn't do anything

#121669 removed a bunch of conditional diagnostic stashing/canceling, but left around the `steal` calls which just emitted the error eagerly instead of canceling the diagnostic. I think that these no-op `steal` calls don't do much and are confusing to encounter, so let's remove them.

The net effect is:
1. We emit more duplicated errors, since stashing has the side effect of duplicating diagnostics. This is not a big deal, since outside of `-Zdeduplicate-diagnostics=no`, the errors are already being deduplicated by the compiler.
2. It changes the order of diagnostics, since we're no longer stashing and then later stealing the errors. I don't think this matters much for the changes that the UI test suite manifests, and it makes these errors less order dependent.

1 files changed, 1 insertions, 11 deletions

diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 2d69386176b..bf0ccdc0f10 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -32,7 +32,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
-use rustc_errors::{Diag, ErrorGuaranteed, StashKey};
+use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::LangItem;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
@@ -782,18 +782,8 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
     pub fn build_mismatch_error(
         &self,
         other: &Self,
-        opaque_def_id: LocalDefId,
         tcx: TyCtxt<'tcx>,
     ) -> Result<Diag<'tcx>, ErrorGuaranteed> {
-        // We used to cancel here for slightly better error messages, but
-        // cancelling stashed diagnostics is no longer allowed because it
-        // causes problems when tracking whether errors have actually
-        // occurred.
-        tcx.sess.dcx().try_steal_modify_and_emit_err(
-            tcx.def_span(opaque_def_id),
-            StashKey::OpaqueHiddenTypeMismatch,
-            |_err| {},
-        );
         (self.ty, other.ty).error_reported()?;
         // Found different concrete types for the opaque type.
         let sub_diag = if self.span == other.span {