Fix typo in AST predicates (#1462)

Author: mjmahone

src/language/kinds.js

@@ -18,7 +18,6 @@ export const Kind = Object.freeze({
   DOCUMENT: 'Document',
   OPERATION_DEFINITION: 'OperationDefinition',
   VARIABLE_DEFINITION: 'VariableDefinition',
-  VARIABLE: 'Variable',
   SELECTION_SET: 'SelectionSet',
   FIELD: 'Field',
   ARGUMENT: 'Argument',
@@ -29,6 +28,7 @@ export const Kind = Object.freeze({
   FRAGMENT_DEFINITION: 'FragmentDefinition',
 
   // Values
+  VARIABLE: 'Variable',
   INT: 'IntValue',
   FLOAT: 'FloatValue',
   STRING: 'StringValue',

src/language/predicates.js

@@ -35,15 +35,15 @@ export function isSelectionNode(node: ASTNode): boolean %checks {
 
 export function isValueNode(node: ASTNode): boolean %checks {
   return (
+    node.kind === Kind.VARIABLE ||
     node.kind === Kind.INT ||
     node.kind === Kind.FLOAT ||
     node.kind === Kind.STRING ||
     node.kind === Kind.BOOLEAN ||
     node.kind === Kind.NULL ||
     node.kind === Kind.ENUM ||
     node.kind === Kind.LIST ||
-    node.kind === Kind.OBJECT ||
-    node.kind === Kind.OBJECT_FIELD
+    node.kind === Kind.OBJECT
   );
 }