Report why it's deleted

Author: AaronBallman

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10176,6 +10176,9 @@ def note_defaulted_comparison_no_viable_function_synthesized : Note<
 def note_defaulted_comparison_not_rewritten_callee : Note<
   "defaulted %0 is implicitly deleted because this non-rewritten comparison "
   "function would be the best match for the comparison">;
+def note_defaulted_comparison_vector_types : Note<
+  "defaulted %0 is implicitly deleted because defaulted comparison of vector "
+  "types is not supported">;
 def note_defaulted_comparison_not_rewritten_conversion : Note<
   "defaulted %0 is implicitly deleted because a builtin comparison function "
   "using this conversion would be the best match for the comparison">;

clang/lib/Sema/SemaDeclCXX.cpp

@@ -8653,8 +8653,15 @@ class DefaultedComparisonAnalyzer
 
         // FIXME: If the type we deduced is a vector type, we mark the
         // comparison as deleted because we don't yet support this.
-        if (isa<VectorType>(T))
+        if (isa<VectorType>(T)) {
+          if (Diagnose == ExplainDeleted) {
+            S.Diag(FD->getLocation(),
+                   diag::note_defaulted_comparison_vector_types)
+                << FD;
+            S.Diag(Subobj.Decl->getLocation(), diag::note_declared_at);
+          }
           return Result::deleted();
+        }
 
         if (NeedsDeducing) {
           std::optional<ComparisonCategoryType> Cat =

clang/test/SemaCXX/cxx2a-three-way-comparison.cpp

@@ -61,8 +61,9 @@ namespace PR44325 {
 
 namespace GH137452 {
 struct comparable_t {
-    __attribute__((vector_size(32))) double numbers;
+    __attribute__((vector_size(32))) double numbers;           // expected-note {{declared here}}
     auto operator<=>(const comparable_t& rhs) const = default; // expected-warning {{explicitly defaulted three-way comparison operator is implicitly deleted}} \
-                                                                  expected-note {{replace 'default' with 'delete'}}
+                                                                  expected-note {{replace 'default' with 'delete'}} \
+                                                                  expected-note {{defaulted 'operator<=>' is implicitly deleted because defaulted comparison of vector types is not supported}}
 };
 } // namespace GH137452