Convert UnionOrIntersectionType.couldContainTypeVariables to ObjectFlags

...to save space (and possibly to reduce de-opts, since it appears to be
lazily set).

Author: amcasey

src/compiler/checker.ts

@@ -17740,18 +17740,18 @@ namespace ts {
         // results for union and intersection types for performance reasons.
         function couldContainTypeVariables(type: Type): boolean {
             const objectFlags = getObjectFlags(type);
-            return !!(type.flags & TypeFlags.Instantiable ||
+            if (objectFlags & ObjectFlags.CouldContainTypeVariablesComputed) {
+                return !!(objectFlags & ObjectFlags.CouldContainTypeVariables);
+            }
+            const result = !!(type.flags & TypeFlags.Instantiable ||
                 objectFlags & ObjectFlags.Reference && ((<TypeReference>type).node || forEach(getTypeArguments(<TypeReference>type), couldContainTypeVariables)) ||
                 objectFlags & ObjectFlags.Anonymous && type.symbol && type.symbol.flags & (SymbolFlags.Function | SymbolFlags.Method | SymbolFlags.Class | SymbolFlags.TypeLiteral | SymbolFlags.ObjectLiteral) && type.symbol.declarations ||
                 objectFlags & (ObjectFlags.Mapped | ObjectFlags.ObjectRestType) ||
-                type.flags & TypeFlags.UnionOrIntersection && !(type.flags & TypeFlags.EnumLiteral) && couldUnionOrIntersectionContainTypeVariables(<UnionOrIntersectionType>type));
-        }
-
-        function couldUnionOrIntersectionContainTypeVariables(type: UnionOrIntersectionType): boolean {
-            if (type.couldContainTypeVariables === undefined) {
-                type.couldContainTypeVariables = some(type.types, couldContainTypeVariables);
+                type.flags & TypeFlags.UnionOrIntersection && !(type.flags & TypeFlags.EnumLiteral) && some((<UnionOrIntersectionType>type).types, couldContainTypeVariables));
+            if (type.flags & TypeFlags.ObjectFlagsType) {
+                (<ObjectFlagsType>type).objectFlags |= ObjectFlags.CouldContainTypeVariablesComputed | (result ? ObjectFlags.CouldContainTypeVariables : 0);
             }
-            return type.couldContainTypeVariables;
+            return result;
         }
 
         function isTypeParameterAtTopLevel(type: Type, typeParameter: TypeParameter): boolean {

src/compiler/types.ts

@@ -4459,6 +4459,10 @@ namespace ts {
         IsGenericIndexTypeComputed = 1 << 24, // IsGenericIndexType flag has been computed
         /* @internal */
         IsGenericIndexType = 1 << 25, // Union or intersection contains generic index type
+        /* @internal */
+        CouldContainTypeVariablesComputed = 1 << 26, // CouldContainTypeVariables flag has been computed
+        /* @internal */
+        CouldContainTypeVariables = 1 << 27, // Type could contain a type variable
         ClassOrInterface = Class | Interface,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectOrArrayLiteral,
@@ -4577,8 +4581,6 @@ namespace ts {
         resolvedStringIndexType: IndexType;
         /* @internal */
         resolvedBaseConstraint: Type;
-        /* @internal */
-        couldContainTypeVariables: boolean;
     }
 
     export interface UnionType extends UnionOrIntersectionType {