[clang][Interp] Fix calling virtual CXXOperatorCallExprs

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -3341,7 +3341,8 @@ bool ByteCodeExprGen<Emitter>::VisitCallExpr(const CallExpr *E) {
     // write the result into.
     if (IsVirtual && !HasQualifier) {
       uint32_t VarArgSize = 0;
-      unsigned NumParams = Func->getNumWrittenParams();
+      unsigned NumParams =
+          Func->getNumWrittenParams() + isa<CXXOperatorCallExpr>(E);
       for (unsigned I = NumParams, N = E->getNumArgs(); I != N; ++I)
         VarArgSize += align(primSize(classify(E->getArg(I)).value_or(PT_Ptr)));
 

clang/test/AST/Interp/records.cpp

@@ -1467,3 +1467,16 @@ namespace IgnoredCtorWithZeroInit {
     return (S(), true);
   }
 }
+
+#if __cplusplus >= 202002L
+namespace VirtOperator {
+  /// This used to crash because it's a virtual CXXOperatorCallExpr.
+  struct B {
+    virtual constexpr bool operator==(const B&) const { return true; }
+  };
+  struct D : B {
+    constexpr bool operator==(const B&) const override{ return false; } // both-note {{operator}}
+  };
+  constexpr bool cmp_base_derived = D() == D(); // both-warning {{ambiguous}}
+}
+#endif