[experiment] Why are we stashing diagnostics on the good path 🤔

compiler/rustc_errors/src/lib.rs

@@ -625,7 +625,6 @@ pub enum StashKey {
     /// FRU syntax
     MaybeFruTypo,
     CallAssocMethod,
-    AssociatedTypeSuggestion,
     /// Query cycle detected, stashing in favor of a better error.
     Cycle,
     UndeterminedMacroResolution,
@@ -983,7 +982,9 @@ impl<'a> DiagCtxtHandle<'a> {
     }
 
     pub fn has_stashed_diagnostic(&self, span: Span, key: StashKey) -> bool {
-        self.inner.borrow().stashed_diagnostics.get(&(span.with_parent(None), key)).is_some()
+        let inner = self.inner.borrow();
+        !inner.stashed_diagnostics.is_empty()
+            && inner.stashed_diagnostics.get(&(span.with_parent(None), key)).is_some()
     }
 
     /// Emit all stashed diagnostics.

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -1,6 +1,6 @@
 use rustc_ast::TraitObjectSyntax;
 use rustc_errors::codes::*;
-use rustc_errors::{Diag, EmissionGuarantee, ErrorGuaranteed, StashKey, Suggestions};
+use rustc_errors::{Diag, EmissionGuarantee, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace, Res};
 use rustc_hir::def_id::DefId;
@@ -100,16 +100,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 poly_trait_ref.trait_ref.trait_def_id(),
                 &mut diag,
             );
-            // In case there is an associated type with the same name
-            // Add the suggestion to this error
-            if let Some(mut sugg) =
-                tcx.dcx().steal_non_err(self_ty.span, StashKey::AssociatedTypeSuggestion)
-                && let Suggestions::Enabled(ref mut s1) = diag.suggestions
-                && let Suggestions::Enabled(ref mut s2) = sugg.suggestions
-            {
-                s1.append(s2);
-                sugg.cancel();
-            }
             Some(diag.emit())
         } else {
             tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, |lint| {

compiler/rustc_resolve/src/late.rs

@@ -20,9 +20,7 @@ use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
-use rustc_errors::{
-    Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, StashKey, Suggestions,
-};
+use rustc_errors::{Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, Suggestions};
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LOCAL_CRATE, LocalDefId};
@@ -4340,29 +4338,6 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             finalize,
         ) {
             Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
-                // if we also have an associated type that matches the ident, stash a suggestion
-                if let Some(items) = self.diag_metadata.current_trait_assoc_items
-                    && let [Segment { ident, .. }] = path
-                    && items.iter().any(|item| {
-                        if let AssocItemKind::Type(alias) = &item.kind
-                            && alias.ident == *ident
-                        {
-                            true
-                        } else {
-                            false
-                        }
-                    })
-                {
-                    let mut diag = self.r.tcx.dcx().struct_allow("");
-                    diag.span_suggestion_verbose(
-                        path_span.shrink_to_lo(),
-                        "there is an associated type with the same name",
-                        "Self::",
-                        Applicability::MaybeIncorrect,
-                    );
-                    diag.stash(path_span, StashKey::AssociatedTypeSuggestion);
-                }
-
                 if source.is_expected(res) || res == Res::Err {
                     partial_res
                 } else {

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -7,8 +7,8 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{
-    Applicability, Diag, ErrorGuaranteed, Level, MultiSpan, StashKey, StringPart, Suggestions,
-    pluralize, struct_span_code_err,
+    Applicability, Diag, ErrorGuaranteed, Level, MultiSpan, StashKey, StringPart, pluralize,
+    struct_span_code_err,
 };
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::intravisit::Visitor;
@@ -2446,15 +2446,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 obligation.cause.code(),
             );
             self.suggest_unsized_bound_if_applicable(err, obligation);
-            if let Some(span) = err.span.primary_span()
-                && let Some(mut diag) =
-                    self.dcx().steal_non_err(span, StashKey::AssociatedTypeSuggestion)
-                && let Suggestions::Enabled(ref mut s1) = err.suggestions
-                && let Suggestions::Enabled(ref mut s2) = diag.suggestions
-            {
-                s1.append(s2);
-                diag.cancel()
-            }
         }
     }