[C++20] Fix a crash with spaceship and vector types

Vector types cannot be directly compared, you get an error when you try
to do so. This patch causes the explicitly defaulted spaceship operator
to be implicitly deleted.

Fixes #137452

Author: AaronBallman

clang/docs/ReleaseNotes.rst

@@ -118,6 +118,9 @@ C++23 Feature Support
 
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
+- Fixed a crash with a defaulted spaceship (``<=>``) operator when the class
+  contains a member declaration of vector type. Vector types cannot yet be
+  compared directly, so this causes the operator to be deleted. (#GH137452)
 
 C++17 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaDeclCXX.cpp

@@ -8651,6 +8651,11 @@ class DefaultedComparisonAnalyzer
         assert(Best->BuiltinParamTypes[2].isNull() &&
                "invalid builtin comparison");
 
+        // 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))
+          return Result::deleted();
+
         if (NeedsDeducing) {
           std::optional<ComparisonCategoryType> Cat =
               getComparisonCategoryForBuiltinCmp(T);

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

@@ -58,3 +58,11 @@ namespace PR44325 {
   // implicit rewrite rules, not for explicit use by programs.
   bool c = cmp_cat() < 0; // expected-warning {{zero as null pointer constant}}
 }
+
+namespace GH137452 {
+struct comparable_t {
+    __attribute__((vector_size(32))) double numbers;
+    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'}}
+};
+} // namespace GH137452