Fix issue with unions not being marked primitive-only

Author: ahejlsberg

Diff for: src/compiler/types.ts

@@ -5008,7 +5008,7 @@ namespace ts {
         // This *should* be every type other than null, undefined, void, and never
         Narrowable = Any | Unknown | StructuredOrInstantiable | StringLike | NumberLike | BigIntLike | BooleanLike | ESSymbol | UniqueESSymbol | NonPrimitive,
         /* @internal */
-        NotPrimitiveUnion = Any | Unknown | Enum | Void | Never | StructuredOrInstantiable,
+        NotPrimitiveUnion = Any | Unknown | Enum | Void | Never | Object | Intersection | Instantiable,
         // The following flags are aggregated during union and intersection type construction
         /* @internal */
         IncludesMask = Any | Unknown | Primitive | Never | Object | Union | Intersection | NonPrimitive | TemplateLiteral,