Convert a few cycles to use objectValues (#1649)

Author: IvanGoncharov

src/type/schema.js

@@ -167,8 +167,7 @@ export class GraphQLSchema {
 
     // Keep track of all implementations by interface name.
     this._implementations = Object.create(null);
-    for (const typeName of Object.keys(this._typeMap)) {
-      const type = this._typeMap[typeName];
+    for (const type of objectValues(this._typeMap)) {
       if (isObjectType(type)) {
         for (const iface of type.getInterfaces()) {
           if (isInterfaceType(iface)) {

src/validation/rules/ValuesOfCorrectType.js

@@ -27,6 +27,7 @@ import inspect from '../../jsutils/inspect';
 import isInvalid from '../../jsutils/isInvalid';
 import keyMap from '../../jsutils/keyMap';
 import orList from '../../jsutils/orList';
+import objectValues from '../../jsutils/objectValues';
 import suggestionList from '../../jsutils/suggestionList';
 
 export function badValueMessage(
@@ -94,16 +95,14 @@ export function ValuesOfCorrectType(context: ValidationContext): ASTVisitor {
         return false; // Don't traverse further.
       }
       // Ensure every required field exists.
-      const inputFields = type.getFields();
       const fieldNodeMap = keyMap(node.fields, field => field.name.value);
-      for (const fieldName of Object.keys(inputFields)) {
-        const fieldDef = inputFields[fieldName];
-        const fieldNode = fieldNodeMap[fieldName];
+      for (const fieldDef of objectValues(type.getFields())) {
+        const fieldNode = fieldNodeMap[fieldDef.name];
         if (!fieldNode && isRequiredInputField(fieldDef)) {
           const typeStr = inspect(fieldDef.type);
           context.reportError(
             new GraphQLError(
-              requiredFieldMessage(type.name, fieldName, typeStr),
+              requiredFieldMessage(type.name, fieldDef.name, typeStr),
               node,
             ),
           );