Revert some failed changes

Author: YexuanXiao

clang/lib/Sema/SemaDeclCXX.cpp

@@ -16715,9 +16715,8 @@ static bool CheckOperatorNewDeclaration(Sema &SemaRef, FunctionDecl *FnDecl) {
   if (CheckOperatorNewDeleteDeclarationScope(SemaRef, FnDecl))
     return true;
 
-  CanQualType SizeTy = SemaRef.Context.getCanonicalType(
-      SemaRef.Context.getCGlobalCXXStdNSTypedef(
-          SemaRef.getStdNamespace(), "size_t", SemaRef.Context.getSizeType()));
+  CanQualType SizeTy =
+      SemaRef.Context.getCanonicalType(SemaRef.Context.getSizeType());
 
   // C++ [basic.stc.dynamic.allocation]p1:
   //  The return type shall be void*. The first parameter shall have type

clang/test/AST/ast-dump-expr-json.cpp

@@ -1545,7 +1545,7 @@ void TestNonADLCall3() {
 // CHECK-NEXT:         }
 // CHECK-NEXT:        },
 // CHECK-NEXT:        "type": {
-// CHECK-NEXT:         "qualType": "size_t"
+// CHECK-NEXT:         "qualType": "unsigned long"
 // CHECK-NEXT:        },
 // CHECK-NEXT:        "valueCategory": "prvalue",
 // CHECK-NEXT:        "name": "Ts"