Flow: use only type imports for importing types (#3097)

Author: IvanGoncharov

src/type/schema.js

@@ -23,12 +23,9 @@ import type {
   GraphQLObjectType,
   GraphQLInterfaceType,
 } from './definition';
+import type { GraphQLDirective } from './directives';
 import { __Schema } from './introspection';
-import {
-  GraphQLDirective,
-  isDirective,
-  specifiedDirectives,
-} from './directives';
+import { isDirective, specifiedDirectives } from './directives';
 import {
   isObjectType,
   isInterfaceType,

src/validation/__tests__/harness.js

@@ -2,7 +2,7 @@ import { expect } from 'chai';
 
 import { parse } from '../../language/parser';
 
-import { GraphQLSchema } from '../../type/schema';
+import type { GraphQLSchema } from '../../type/schema';
 
 import { buildSchema } from '../../utilities/buildASTSchema';