Cache results of isGenericObjectType and isGenericIndexType (microsoft#36622)

Author: ahejlsberg

src/compiler/checker.ts

@@ -12498,11 +12498,25 @@ namespace ts {
         }
 
         function isGenericObjectType(type: Type): boolean {
-            return maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive | TypeFlags.GenericMappedType);
+            if (type.flags & TypeFlags.UnionOrIntersection) {
+                if (!((<UnionOrIntersectionType>type).objectFlags & ObjectFlags.IsGenericObjectTypeComputed)) {
+                    (<UnionOrIntersectionType>type).objectFlags |= ObjectFlags.IsGenericObjectTypeComputed |
+                        (some((<UnionOrIntersectionType>type).types, isGenericObjectType) ? ObjectFlags.IsGenericObjectType : 0);
+                }
+                return !!((<UnionOrIntersectionType>type).objectFlags & ObjectFlags.IsGenericObjectType);
+            }
+            return !!(type.flags & TypeFlags.InstantiableNonPrimitive) || isGenericMappedType(type);
         }
 
         function isGenericIndexType(type: Type): boolean {
-            return maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive | TypeFlags.Index);
+            if (type.flags & TypeFlags.UnionOrIntersection) {
+                if (!((<UnionOrIntersectionType>type).objectFlags & ObjectFlags.IsGenericIndexTypeComputed)) {
+                    (<UnionOrIntersectionType>type).objectFlags |= ObjectFlags.IsGenericIndexTypeComputed |
+                        (some((<UnionOrIntersectionType>type).types, isGenericIndexType) ? ObjectFlags.IsGenericIndexType : 0);
+                }
+                return !!((<UnionOrIntersectionType>type).objectFlags & ObjectFlags.IsGenericIndexType);
+            }
+            return !!(type.flags & (TypeFlags.InstantiableNonPrimitive | TypeFlags.Index));
         }
 
         function isThisTypeParameter(type: Type): boolean {
@@ -12726,7 +12740,7 @@ namespace ts {
             if (checkType === wildcardType || extendsType === wildcardType) {
                 return wildcardType;
             }
-            const checkTypeInstantiable = maybeTypeOfKind(checkType, TypeFlags.Instantiable | TypeFlags.GenericMappedType);
+            const checkTypeInstantiable = isGenericObjectType(checkType) || isGenericIndexType(checkType);
             let combinedMapper: TypeMapper | undefined;
             if (root.inferTypeParameters) {
                 const context = createInferenceContext(root.inferTypeParameters, /*signature*/ undefined, InferenceFlags.None);
@@ -12745,7 +12759,7 @@ namespace ts {
             // Instantiate the extends type including inferences for 'infer T' type parameters
             const inferredExtendsType = combinedMapper ? instantiateType(root.extendsType, combinedMapper) : extendsType;
             // We attempt to resolve the conditional type only when the check and extends types are non-generic
-            if (!checkTypeInstantiable && !maybeTypeOfKind(inferredExtendsType, TypeFlags.Instantiable | TypeFlags.GenericMappedType)) {
+            if (!checkTypeInstantiable && !isGenericObjectType(inferredExtendsType) && !isGenericIndexType(inferredExtendsType)) {
                 if (inferredExtendsType.flags & TypeFlags.AnyOrUnknown) {
                     return instantiateType(root.trueType, combinedMapper || mapper);
                 }
@@ -27037,7 +27051,7 @@ namespace ts {
         // Return true if type might be of the given kind. A union or intersection type might be of a given
         // kind if at least one constituent type is of the given kind.
         function maybeTypeOfKind(type: Type, kind: TypeFlags): boolean {
-            if (type.flags & kind & ~TypeFlags.GenericMappedType || kind & TypeFlags.GenericMappedType && isGenericMappedType(type)) {
+            if (type.flags & kind) {
                 return true;
             }
             if (type.flags & TypeFlags.UnionOrIntersection) {

src/compiler/types.ts

@@ -4348,9 +4348,6 @@ namespace ts {
         IncludesWildcard = Index,
         /* @internal */
         IncludesEmptyObject = IndexedAccess,
-        // The following flag is used for different purposes by maybeTypeOfKind
-        /* @internal */
-        GenericMappedType = Never,
     }
 
     export type DestructuringPattern = BindingPattern | ObjectLiteralExpression | ArrayLiteralExpression;
@@ -4454,6 +4451,14 @@ namespace ts {
         ContainsObjectOrArrayLiteral = 1 << 20, // Type is or contains object literal type
         /* @internal */
         NonInferrableType = 1 << 21, // Type is or contains anyFunctionType or silentNeverType
+        /* @internal */
+        IsGenericObjectTypeComputed = 1 << 22, // IsGenericObjectType flag has been computed
+        /* @internal */
+        IsGenericObjectType = 1 << 23, // Union or intersection contains generic object type
+        /* @internal */
+        IsGenericIndexTypeComputed = 1 << 24, // IsGenericIndexType flag has been computed
+        /* @internal */
+        IsGenericIndexType = 1 << 25, // Union or intersection contains generic index type
         ClassOrInterface = Class | Interface,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectOrArrayLiteral,