[clang] Only use CheckVectorOperands for fixed-length vector operands

Fixes #170279

Author: MacDue

clang/lib/Sema/SemaExprCXX.cpp

@@ -5724,12 +5724,14 @@ QualType Sema::CheckVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
       ResultType = CheckSizelessVectorOperands(LHS, RHS, QuestionLoc,
                                                /*IsCompAssign*/ false,
                                                ArithConvKind::Conditional);
-    else
+    else if (LHSType->isVectorType() || LHSType->isVectorType())
       ResultType = CheckVectorOperands(
           LHS, RHS, QuestionLoc, /*isCompAssign*/ false, /*AllowBothBool*/ true,
           /*AllowBoolConversions*/ false,
           /*AllowBoolOperation*/ true,
           /*ReportInvalid*/ true);
+    else
+      return InvalidOperands(QuestionLoc, LHS, RHS);
     if (ResultType.isNull())
       return {};
   } else {

clang/test/Sema/AArch64/sve-vector-conditional-op.cpp

@@ -22,6 +22,16 @@ auto error_sve_vector_result_matched_element_count(__SVBool_t svbool, __SVUint32
   return svbool ? a : b;
 }
 
+auto error_fixed_cond_mixed_scalar_and_vector_operands(fixed_vector cond, unsigned char a, __SVUint8_t b) {
+  // expected-error@+1 {{invalid operands to binary expression ('unsigned char' and '__SVUint8_t')}}
+  return cond ? a : b;
+}
+
+auto error_scalable_cond_mixed_scalar_and_vector_operands(__SVBool_t svbool, unsigned char a, fixed_vector b) {
+  // expected-error@+1 {{cannot convert between vector and non-scalar values ('unsigned char' and 'fixed_vector' (vector of 1 'int' value))}}
+  return svbool ? a : b;
+}
+
 // The following cases should be supported:
 
 __SVBool_t cond_svbool(__SVBool_t a, __SVBool_t b) {