classify nonPrimitive type as narrowable rather than structured

Author: HerringtonDarkholme

src/compiler/types.ts

@@ -2799,13 +2799,13 @@ namespace ts {
         BooleanLike = Boolean | BooleanLiteral,
         EnumLike = Enum | EnumLiteral,
         UnionOrIntersection = Union | Intersection,
-        StructuredType = Object | Union | Intersection | NonPrimitive,
+        StructuredType = Object | Union | Intersection,
         StructuredOrTypeParameter = StructuredType | TypeParameter | Index,
         TypeVariable = TypeParameter | IndexedAccess,
 
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
-        Narrowable = Any | StructuredType | TypeParameter | Index | IndexedAccess | StringLike | NumberLike | BooleanLike | ESSymbol,
+        Narrowable = Any | StructuredType | TypeParameter | Index | IndexedAccess | StringLike | NumberLike | BooleanLike | ESSymbol | NonPrimitive,
         NotUnionOrUnit = Any | ESSymbol | Object | NonPrimitive,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectLiteral,