TS: introspectionTypes should be array of GraphQLNamedType (#2261)

Author: pcarrier

src/type/introspection.d.ts

@@ -2,7 +2,7 @@ import {
   GraphQLObjectType,
   GraphQLField,
   GraphQLEnumType,
-  GraphQLType,
+  GraphQLNamedType,
 } from './definition';
 
 export const __Schema: GraphQLObjectType;
@@ -35,6 +35,6 @@ export const SchemaMetaFieldDef: GraphQLField<any, any>;
 export const TypeMetaFieldDef: GraphQLField<any, any>;
 export const TypeNameMetaFieldDef: GraphQLField<any, any>;
 
-export const introspectionTypes: ReadonlyArray<GraphQLType>;
+export const introspectionTypes: ReadonlyArray<GraphQLNamedType>;
 
-export function isIntrospectionType(type: GraphQLType): boolean;
+export function isIntrospectionType(type: GraphQLNamedType): boolean;