diff --git a/docs/reference.md b/docs/reference.md
index aa033dc..1f86412 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -374,28 +374,28 @@ public $variableValues;
  */
 function getFieldSelection($depth = 0)
 ```
-# GraphQL\Type\Definition\DirectiveLocation
+# GraphQL\Language\DirectiveLocation
 List of available directive locations
 
 **Class Constants:** 
 ```php
-const IFACE = "INTERFACE";
-const SUBSCRIPTION = "SUBSCRIPTION";
-const FRAGMENT_SPREAD = "FRAGMENT_SPREAD";
 const QUERY = "QUERY";
 const MUTATION = "MUTATION";
+const SUBSCRIPTION = "SUBSCRIPTION";
+const FIELD = "FIELD";
 const FRAGMENT_DEFINITION = "FRAGMENT_DEFINITION";
-const INPUT_OBJECT = "INPUT_OBJECT";
+const FRAGMENT_SPREAD = "FRAGMENT_SPREAD";
 const INLINE_FRAGMENT = "INLINE_FRAGMENT";
-const UNION = "UNION";
+const SCHEMA = "SCHEMA";
 const SCALAR = "SCALAR";
+const OBJECT = "OBJECT";
 const FIELD_DEFINITION = "FIELD_DEFINITION";
 const ARGUMENT_DEFINITION = "ARGUMENT_DEFINITION";
+const IFACE = "INTERFACE";
+const UNION = "UNION";
 const ENUM = "ENUM";
-const OBJECT = "OBJECT";
 const ENUM_VALUE = "ENUM_VALUE";
-const FIELD = "FIELD";
-const SCHEMA = "SCHEMA";
+const INPUT_OBJECT = "INPUT_OBJECT";
 const INPUT_FIELD_DEFINITION = "INPUT_FIELD_DEFINITION";
 ```
 
@@ -936,7 +936,7 @@ const UNION_TYPE_DEFINITION = "UnionTypeDefinition";
 const ENUM_TYPE_DEFINITION = "EnumTypeDefinition";
 const ENUM_VALUE_DEFINITION = "EnumValueDefinition";
 const INPUT_OBJECT_TYPE_DEFINITION = "InputObjectTypeDefinition";
-const TYPE_EXTENSION_DEFINITION = "TypeExtensionDefinition";
+const OBJECT_TYPE_EXTENSION = "ObjectTypeExtension";
 const DIRECTIVE_DEFINITION = "DirectiveDefinition";
 ```
 
diff --git a/docs/type-system/directives.md b/docs/type-system/directives.md
index 6b12588..454ce4c 100644
--- a/docs/type-system/directives.md
+++ b/docs/type-system/directives.md
@@ -35,9 +35,9 @@ In **graphql-php** custom directive is an instance of `GraphQL\Type\Definition\D
 
 ```php
 <?php
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\Directive;
-use GraphQL\Type\Definition\DirectiveLocation;
 use GraphQL\Type\Definition\FieldArgument;
 
 $trackDirective = new Directive([
diff --git a/src/Executor/Executor.php b/src/Executor/Executor.php
index c21db83..fab555a 100644
--- a/src/Executor/Executor.php
+++ b/src/Executor/Executor.php
@@ -211,11 +211,6 @@ class Executor
                 case NodeKind::FRAGMENT_DEFINITION:
                     $fragments[$definition->name->value] = $definition;
                     break;
-                default:
-                    throw new Error(
-                        "GraphQL cannot execute a request containing a {$definition->kind}.",
-                        [$definition]
-                    );
             }
         }
 
diff --git a/src/Language/AST/NodeKind.php b/src/Language/AST/NodeKind.php
index e797618..22287c4 100644
--- a/src/Language/AST/NodeKind.php
+++ b/src/Language/AST/NodeKind.php
@@ -65,7 +65,7 @@ class NodeKind
 
     // Type Extensions
 
-    const TYPE_EXTENSION_DEFINITION = 'TypeExtensionDefinition';
+    const OBJECT_TYPE_EXTENSION = 'ObjectTypeExtension';
 
     // Directive Definitions
 
@@ -127,7 +127,7 @@ class NodeKind
         NodeKind::INPUT_OBJECT_TYPE_DEFINITION =>InputObjectTypeDefinitionNode::class,
 
         // Type Extensions
-        NodeKind::TYPE_EXTENSION_DEFINITION => TypeExtensionDefinitionNode::class,
+        NodeKind::OBJECT_TYPE_EXTENSION => ObjectTypeExtensionNode::class,
 
         // Directive Definitions
         NodeKind::DIRECTIVE_DEFINITION => DirectiveDefinitionNode::class
diff --git a/src/Language/AST/ObjectTypeExtensionNode.php b/src/Language/AST/ObjectTypeExtensionNode.php
new file mode 100644
index 0000000..c8eab0a
--- /dev/null
+++ b/src/Language/AST/ObjectTypeExtensionNode.php
@@ -0,0 +1,30 @@
+<?php
+namespace GraphQL\Language\AST;
+
+class ObjectTypeExtensionNode extends Node implements TypeExtensionNode
+{
+    /**
+     * @var string
+     */
+    public $kind = NodeKind::OBJECT_TYPE_EXTENSION;
+
+    /**
+     * @var NameNode
+     */
+    public $name;
+
+    /**
+     * @var NamedTypeNode[]
+     */
+    public $interfaces = [];
+
+    /**
+     * @var DirectiveNode[]
+     */
+    public $directives;
+
+    /**
+     * @var FieldDefinitionNode[]
+     */
+    public $fields;
+}
diff --git a/src/Language/AST/TypeExtensionDefinitionNode.php b/src/Language/AST/TypeExtensionDefinitionNode.php
deleted file mode 100644
index ca73157..0000000
--- a/src/Language/AST/TypeExtensionDefinitionNode.php
+++ /dev/null
@@ -1,15 +0,0 @@
-<?php
-namespace GraphQL\Language\AST;
-
-class TypeExtensionDefinitionNode extends Node implements TypeSystemDefinitionNode
-{
-    /**
-     * @var string
-     */
-    public $kind = NodeKind::TYPE_EXTENSION_DEFINITION;
-
-    /**
-     * @var ObjectTypeDefinitionNode
-     */
-    public $definition;
-}
diff --git a/src/Language/AST/TypeExtensionNode.php b/src/Language/AST/TypeExtensionNode.php
new file mode 100644
index 0000000..db50f2a
--- /dev/null
+++ b/src/Language/AST/TypeExtensionNode.php
@@ -0,0 +1,10 @@
+<?php
+namespace GraphQL\Language\AST;
+
+interface TypeExtensionNode extends TypeSystemDefinitionNode
+{
+    /**
+    export type TypeExtensionNode =
+      | ObjectTypeExtensionNode;
+     */
+}
diff --git a/src/Language/AST/TypeSystemDefinitionNode.php b/src/Language/AST/TypeSystemDefinitionNode.php
index 1299aa2..60a9fda 100644
--- a/src/Language/AST/TypeSystemDefinitionNode.php
+++ b/src/Language/AST/TypeSystemDefinitionNode.php
@@ -4,9 +4,10 @@ namespace GraphQL\Language\AST;
 interface TypeSystemDefinitionNode extends DefinitionNode
 {
     /**
-    export type TypeSystemDefinitionNode = SchemaDefinitionNode
+    export type TypeSystemDefinitionNode =
+    | SchemaDefinitionNode
     | TypeDefinitionNode
-    | TypeExtensionDefinitionNode
+    | TypeExtensionNode
     | DirectiveDefinitionNode
      */
 }
diff --git a/src/Language/DirectiveLocation.php b/src/Language/DirectiveLocation.php
new file mode 100644
index 0000000..a9e22e2
--- /dev/null
+++ b/src/Language/DirectiveLocation.php
@@ -0,0 +1,60 @@
+<?php
+namespace GraphQL\Language;
+
+/**
+ * List of available directive locations
+ */
+class DirectiveLocation
+{
+    // Request Definitions
+    const QUERY = 'QUERY';
+    const MUTATION = 'MUTATION';
+    const SUBSCRIPTION = 'SUBSCRIPTION';
+    const FIELD = 'FIELD';
+    const FRAGMENT_DEFINITION = 'FRAGMENT_DEFINITION';
+    const FRAGMENT_SPREAD = 'FRAGMENT_SPREAD';
+    const INLINE_FRAGMENT = 'INLINE_FRAGMENT';
+
+    // Type System Definitions
+    const SCHEMA = 'SCHEMA';
+    const SCALAR = 'SCALAR';
+    const OBJECT = 'OBJECT';
+    const FIELD_DEFINITION = 'FIELD_DEFINITION';
+    const ARGUMENT_DEFINITION = 'ARGUMENT_DEFINITION';
+    const IFACE = 'INTERFACE';
+    const UNION = 'UNION';
+    const ENUM = 'ENUM';
+    const ENUM_VALUE = 'ENUM_VALUE';
+    const INPUT_OBJECT = 'INPUT_OBJECT';
+    const INPUT_FIELD_DEFINITION = 'INPUT_FIELD_DEFINITION';
+
+    private static $locations = [
+        self::QUERY => self::QUERY,
+        self::MUTATION => self::MUTATION,
+        self::SUBSCRIPTION => self::SUBSCRIPTION,
+        self::FIELD => self::FIELD,
+        self::FRAGMENT_DEFINITION => self::FRAGMENT_DEFINITION,
+        self::FRAGMENT_SPREAD => self::FRAGMENT_SPREAD,
+        self::INLINE_FRAGMENT => self::INLINE_FRAGMENT,
+        self::SCHEMA => self::SCHEMA,
+        self::SCALAR => self::SCALAR,
+        self::OBJECT => self::OBJECT,
+        self::FIELD_DEFINITION => self::FIELD_DEFINITION,
+        self::ARGUMENT_DEFINITION => self::ARGUMENT_DEFINITION,
+        self::IFACE => self::IFACE,
+        self::UNION => self::UNION,
+        self::ENUM => self::ENUM,
+        self::ENUM_VALUE => self::ENUM_VALUE,
+        self::INPUT_OBJECT => self::INPUT_OBJECT,
+        self::INPUT_FIELD_DEFINITION => self::INPUT_FIELD_DEFINITION,
+    ];
+
+    /**
+     * @param string $name
+     * @return bool
+     */
+    public static function has($name)
+    {
+        return isset(self::$locations[$name]);
+    }
+}
diff --git a/src/Language/Parser.php b/src/Language/Parser.php
index c0c139c..b5a16fc 100644
--- a/src/Language/Parser.php
+++ b/src/Language/Parser.php
@@ -36,7 +36,8 @@ use GraphQL\Language\AST\ScalarTypeDefinitionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
 use GraphQL\Language\AST\SelectionSetNode;
 use GraphQL\Language\AST\StringValueNode;
-use GraphQL\Language\AST\TypeExtensionDefinitionNode;
+use GraphQL\Language\AST\ObjectTypeExtensionNode;
+use GraphQL\Language\AST\TypeExtensionNode;
 use GraphQL\Language\AST\TypeSystemDefinitionNode;
 use GraphQL\Language\AST\UnionTypeDefinitionNode;
 use GraphQL\Language\AST\VariableNode;
@@ -393,7 +394,7 @@ class Parser
             'operation' => $operation,
             'name' => $name,
             'variableDefinitions' => $this->parseVariableDefinitions(),
-            'directives' => $this->parseDirectives(),
+            'directives' => $this->parseDirectives(false),
             'selectionSet' => $this->parseSelectionSet(),
             'loc' => $this->loc($start)
         ]);
@@ -494,6 +495,7 @@ class Parser
 
     /**
      * @return FieldNode
+     * @throws SyntaxError
      */
     function parseField()
     {
@@ -511,20 +513,23 @@ class Parser
         return new FieldNode([
             'alias' => $alias,
             'name' => $name,
-            'arguments' => $this->parseArguments(),
-            'directives' => $this->parseDirectives(),
+            'arguments' => $this->parseArguments(false),
+            'directives' => $this->parseDirectives(false),
             'selectionSet' => $this->peek(Token::BRACE_L) ? $this->parseSelectionSet() : null,
             'loc' => $this->loc($start)
         ]);
     }
 
     /**
+     * @param bool $isConst
      * @return ArgumentNode[]|NodeList
+     * @throws SyntaxError
      */
-    function parseArguments()
+    function parseArguments($isConst)
     {
+        $item = $isConst ? 'parseConstArgument' : 'parseArgument';
         return $this->peek(Token::PAREN_L) ?
-            $this->many(Token::PAREN_L, [$this, 'parseArgument'], Token::PAREN_R) :
+            $this->many(Token::PAREN_L, [$this, $item], Token::PAREN_R) :
             new NodeList([]);
     }
 
@@ -547,6 +552,25 @@ class Parser
         ]);
     }
 
+    /**
+     * @return ArgumentNode
+     * @throws SyntaxError
+     */
+    function parseConstArgument()
+    {
+        $start = $this->lexer->token;
+        $name = $this->parseName();
+
+        $this->expect(Token::COLON);
+        $value = $this->parseConstValue();
+
+        return new ArgumentNode([
+            'name' => $name,
+            'value' => $value,
+            'loc' => $this->loc($start)
+        ]);
+    }
+
     // Implements the parsing rules in the Fragments section.
 
     /**
@@ -561,7 +585,7 @@ class Parser
         if ($this->peek(Token::NAME) && $this->lexer->token->value !== 'on') {
             return new FragmentSpreadNode([
                 'name' => $this->parseFragmentName(),
-                'directives' => $this->parseDirectives(),
+                'directives' => $this->parseDirectives(false),
                 'loc' => $this->loc($start)
             ]);
         }
@@ -574,7 +598,7 @@ class Parser
 
         return new InlineFragmentNode([
             'typeCondition' => $typeCondition,
-            'directives' => $this->parseDirectives(),
+            'directives' => $this->parseDirectives(false),
             'selectionSet' => $this->parseSelectionSet(),
             'loc' => $this->loc($start)
         ]);
@@ -596,7 +620,7 @@ class Parser
         return new FragmentDefinitionNode([
             'name' => $name,
             'typeCondition' => $typeCondition,
-            'directives' => $this->parseDirectives(),
+            'directives' => $this->parseDirectives(false),
             'selectionSet' => $this->parseSelectionSet(),
             'loc' => $this->loc($start)
         ]);
@@ -775,28 +799,31 @@ class Parser
     // Implements the parsing rules in the Directives section.
 
     /**
+     * @param bool $isConst
      * @return DirectiveNode[]|NodeList
+     * @throws SyntaxError
      */
-    function parseDirectives()
+    function parseDirectives($isConst)
     {
         $directives = [];
         while ($this->peek(Token::AT)) {
-            $directives[] = $this->parseDirective();
+            $directives[] = $this->parseDirective($isConst);
         }
         return new NodeList($directives);
     }
 
     /**
+     * @param bool $isConst
      * @return DirectiveNode
      * @throws SyntaxError
      */
-    function parseDirective()
+    function parseDirective($isConst)
     {
         $start = $this->lexer->token;
         $this->expect(Token::AT);
         return new DirectiveNode([
             'name' => $this->parseName(),
-            'arguments' => $this->parseArguments(),
+            'arguments' => $this->parseArguments($isConst),
             'loc' => $this->loc($start)
         ]);
     }
@@ -849,7 +876,7 @@ class Parser
      * TypeSystemDefinition :
      *   - SchemaDefinition
      *   - TypeDefinition
-     *   - TypeExtensionDefinition
+     *   - TypeExtension
      *   - DirectiveDefinition
      *
      * TypeDefinition :
@@ -879,12 +906,12 @@ class Parser
                 case 'union': return $this->parseUnionTypeDefinition();
                 case 'enum': return $this->parseEnumTypeDefinition();
                 case 'input': return $this->parseInputObjectTypeDefinition();
-                case 'extend': return $this->parseTypeExtensionDefinition();
+                case 'extend': return $this->parseTypeExtension();
                 case 'directive': return $this->parseDirectiveDefinition();
             }
         }
 
-        throw $this->unexpected();
+        throw $this->unexpected($keywordToken);
     }
 
     /**
@@ -911,7 +938,7 @@ class Parser
     {
         $start = $this->lexer->token;
         $this->expectKeyword('schema');
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
 
         $operationTypes = $this->many(
             Token::BRACE_L,
@@ -953,7 +980,7 @@ class Parser
         $description = $this->parseDescription();
         $this->expectKeyword('scalar');
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
 
         return new ScalarTypeDefinitionNode([
             'name' => $name,
@@ -974,13 +1001,8 @@ class Parser
         $this->expectKeyword('type');
         $name = $this->parseName();
         $interfaces = $this->parseImplementsInterfaces();
-        $directives = $this->parseDirectives();
-
-        $fields = $this->any(
-            Token::BRACE_L,
-            [$this, 'parseFieldDefinition'],
-            Token::BRACE_R
-        );
+        $directives = $this->parseDirectives(true);
+        $fields = $this->parseFieldDefinitions();
 
         return new ObjectTypeDefinitionNode([
             'name' => $name,
@@ -1007,6 +1029,19 @@ class Parser
         return $types;
     }
 
+    /**
+     * @return FieldDefinitionNode[]|NodeList
+     * @throws SyntaxError
+     */
+    function parseFieldDefinitions()
+    {
+        return $this->many(
+            Token::BRACE_L,
+            [$this, 'parseFieldDefinition'],
+            Token::BRACE_R
+        );
+    }
+
     /**
      * @return FieldDefinitionNode
      * @throws SyntaxError
@@ -1019,7 +1054,7 @@ class Parser
         $args = $this->parseArgumentDefs();
         $this->expect(Token::COLON);
         $type = $this->parseTypeReference();
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
 
         return new FieldDefinitionNode([
             'name' => $name,
@@ -1057,7 +1092,7 @@ class Parser
         if ($this->skip(Token::EQUALS)) {
             $defaultValue = $this->parseConstValue();
         }
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
         return new InputValueDefinitionNode([
             'name' => $name,
             'type' => $type,
@@ -1078,12 +1113,8 @@ class Parser
         $description = $this->parseDescription();
         $this->expectKeyword('interface');
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
-        $fields = $this->any(
-            Token::BRACE_L,
-            [$this, 'parseFieldDefinition'],
-            Token::BRACE_R
-        );
+        $directives = $this->parseDirectives(true);
+        $fields = $this->parseFieldDefinitions();
 
         return new InterfaceTypeDefinitionNode([
             'name' => $name,
@@ -1104,7 +1135,7 @@ class Parser
         $description = $this->parseDescription();
         $this->expectKeyword('union');
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
         $this->expect(Token::EQUALS);
         $types = $this->parseUnionMembers();
 
@@ -1146,7 +1177,7 @@ class Parser
         $description = $this->parseDescription();
         $this->expectKeyword('enum');
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
         $values = $this->many(
             Token::BRACE_L,
             [$this, 'parseEnumValueDefinition'],
@@ -1164,13 +1195,14 @@ class Parser
 
     /**
      * @return EnumValueDefinitionNode
+     * @throws SyntaxError
      */
     function parseEnumValueDefinition()
     {
         $start = $this->lexer->token;
         $description = $this->parseDescription();
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
+        $directives = $this->parseDirectives(true);
 
         return new EnumValueDefinitionNode([
             'name' => $name,
@@ -1190,8 +1222,8 @@ class Parser
         $description = $this->parseDescription();
         $this->expectKeyword('input');
         $name = $this->parseName();
-        $directives = $this->parseDirectives();
-        $fields = $this->any(
+        $directives = $this->parseDirectives(true);
+        $fields = $this->many(
             Token::BRACE_L,
             [$this, 'parseInputValueDef'],
             Token::BRACE_R
@@ -1207,17 +1239,51 @@ class Parser
     }
 
     /**
-     * @return TypeExtensionDefinitionNode
+     * @return TypeExtensionNode
      * @throws SyntaxError
      */
-    function parseTypeExtensionDefinition()
+    function parseTypeExtension()
     {
+        $keywordToken = $this->lexer->lookahead();
+
+        if ($keywordToken->kind === Token::NAME) {
+            switch ($keywordToken->value) {
+                case 'type':
+                    return $this->parseObjectTypeExtension();
+            }
+        }
+
+        throw $this->unexpected($keywordToken);
+    }
+
+    /**
+     * @return ObjectTypeExtensionNode
+     * @throws SyntaxError
+     */
+    function parseObjectTypeExtension() {
         $start = $this->lexer->token;
         $this->expectKeyword('extend');
-        $definition = $this->parseObjectTypeDefinition();
+        $this->expectKeyword('type');
+        $name = $this->parseName();
+        $interfaces = $this->parseImplementsInterfaces();
+        $directives = $this->parseDirectives(true);
+        $fields = $this->peek(Token::BRACE_L)
+            ? $this->parseFieldDefinitions()
+            : [];
 
-        return new TypeExtensionDefinitionNode([
-            'definition' => $definition,
+        if (
+            count($interfaces) === 0 &&
+            count($directives) === 0 &&
+            count($fields) === 0
+        ) {
+            throw $this->unexpected();
+        }
+
+        return new ObjectTypeExtensionNode([
+            'name' => $name,
+            'interfaces' => $interfaces,
+            'directives' => $directives,
+            'fields' => $fields,
             'loc' => $this->loc($start)
         ]);
     }
@@ -1251,6 +1317,7 @@ class Parser
 
     /**
      * @return NameNode[]
+     * @throws SyntaxError
      */
     function parseDirectiveLocations()
     {
@@ -1258,8 +1325,23 @@ class Parser
         $this->skip(Token::PIPE);
         $locations = [];
         do {
-            $locations[] = $this->parseName();
+            $locations[] = $this->parseDirectiveLocation();
         } while ($this->skip(Token::PIPE));
         return $locations;
     }
+
+    /**
+     * @return NameNode
+     * @throws SyntaxError
+     */
+    function parseDirectiveLocation()
+    {
+        $start = $this->lexer->token;
+        $name = $this->parseName();
+        if (DirectiveLocation::has($name->value)) {
+            return $name;
+        }
+
+        throw $this->unexpected($start);
+    }
 }
diff --git a/src/Language/Printer.php b/src/Language/Printer.php
index 0e5566d..b835b4d 100644
--- a/src/Language/Printer.php
+++ b/src/Language/Printer.php
@@ -35,7 +35,7 @@ use GraphQL\Language\AST\ScalarTypeDefinitionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
 use GraphQL\Language\AST\SelectionSetNode;
 use GraphQL\Language\AST\StringValueNode;
-use GraphQL\Language\AST\TypeExtensionDefinitionNode;
+use GraphQL\Language\AST\ObjectTypeExtensionNode;
 use GraphQL\Language\AST\UnionTypeDefinitionNode;
 use GraphQL\Language\AST\VariableDefinitionNode;
 use GraphQL\Utils\Utils;
@@ -278,8 +278,14 @@ class Printer
                         ], ' ')
                     ], "\n");
                 },
-                NodeKind::TYPE_EXTENSION_DEFINITION => function(TypeExtensionDefinitionNode $def) {
-                    return "extend {$def->definition}";
+                NodeKind::OBJECT_TYPE_EXTENSION => function(ObjectTypeExtensionNode $def) {
+                    return $this->join([
+                        'extend type',
+                        $def->name,
+                        $this->wrap('implements ', $this->join($def->interfaces, ', ')),
+                        $this->join($def->directives, ' '),
+                        $this->block($def->fields),
+                    ], ' ');
                 },
                 NodeKind::DIRECTIVE_DEFINITION => function(DirectiveDefinitionNode $def) {
                     return $this->join([
@@ -309,7 +315,7 @@ class Printer
     {
         return ($array && $this->length($array))
             ? "{\n" . $this->indent($this->join($array, "\n")) . "\n}"
-            : '{}';
+            : '';
     }
 
     public function indent($maybeString)
diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index 9ddca60..fb149cd 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -142,7 +142,7 @@ class Visitor
         NodeKind::ENUM_TYPE_DEFINITION => ['description', 'name', 'directives', 'values'],
         NodeKind::ENUM_VALUE_DEFINITION => ['description', 'name', 'directives'],
         NodeKind::INPUT_OBJECT_TYPE_DEFINITION => ['description', 'name', 'directives', 'fields'],
-        NodeKind::TYPE_EXTENSION_DEFINITION => [ 'definition' ],
+        NodeKind::OBJECT_TYPE_EXTENSION => [ 'name', 'interfaces', 'directives', 'fields' ],
         NodeKind::DIRECTIVE_DEFINITION => ['description', 'name', 'arguments', 'locations']
     ];
 
diff --git a/src/Type/Definition/Directive.php b/src/Type/Definition/Directive.php
index 63ea075..fcf6c2a 100644
--- a/src/Type/Definition/Directive.php
+++ b/src/Type/Definition/Directive.php
@@ -2,6 +2,7 @@
 namespace GraphQL\Type\Definition;
 
 use GraphQL\Language\AST\DirectiveDefinitionNode;
+use GraphQL\Language\DirectiveLocation;
 
 /**
  * Class Directive
@@ -18,35 +19,6 @@ class Directive
 
     // Schema Definitions
 
-
-    /**
-     * @var array
-     * @deprecated as of 8.0 (use DirectiveLocation constants directly)
-     */
-    public static $directiveLocations = [
-        // Operations:
-        DirectiveLocation::QUERY => DirectiveLocation::QUERY,
-        DirectiveLocation::MUTATION => DirectiveLocation::MUTATION,
-        DirectiveLocation::SUBSCRIPTION => DirectiveLocation::SUBSCRIPTION,
-        DirectiveLocation::FIELD => DirectiveLocation::FIELD,
-        DirectiveLocation::FRAGMENT_DEFINITION => DirectiveLocation::FRAGMENT_DEFINITION,
-        DirectiveLocation::FRAGMENT_SPREAD => DirectiveLocation::FRAGMENT_SPREAD,
-        DirectiveLocation::INLINE_FRAGMENT => DirectiveLocation::INLINE_FRAGMENT,
-
-        // Schema Definitions
-        DirectiveLocation::SCHEMA => DirectiveLocation::SCHEMA,
-        DirectiveLocation::SCALAR => DirectiveLocation::SCALAR,
-        DirectiveLocation::OBJECT => DirectiveLocation::OBJECT,
-        DirectiveLocation::FIELD_DEFINITION => DirectiveLocation::FIELD_DEFINITION,
-        DirectiveLocation::ARGUMENT_DEFINITION => DirectiveLocation::ARGUMENT_DEFINITION,
-        DirectiveLocation::IFACE => DirectiveLocation::IFACE,
-        DirectiveLocation::UNION => DirectiveLocation::UNION,
-        DirectiveLocation::ENUM => DirectiveLocation::ENUM,
-        DirectiveLocation::ENUM_VALUE => DirectiveLocation::ENUM_VALUE,
-        DirectiveLocation::INPUT_OBJECT => DirectiveLocation::INPUT_OBJECT,
-        DirectiveLocation::INPUT_FIELD_DEFINITION => DirectiveLocation::INPUT_FIELD_DEFINITION
-    ];
-
     /**
      * @return Directive
      */
diff --git a/src/Type/Definition/DirectiveLocation.php b/src/Type/Definition/DirectiveLocation.php
deleted file mode 100644
index fee4d7a..0000000
--- a/src/Type/Definition/DirectiveLocation.php
+++ /dev/null
@@ -1,27 +0,0 @@
-<?php
-namespace GraphQL\Type\Definition;
-
-/**
- * List of available directive locations
- */
-class DirectiveLocation
-{
-    const IFACE = 'INTERFACE';
-    const SUBSCRIPTION = 'SUBSCRIPTION';
-    const FRAGMENT_SPREAD = 'FRAGMENT_SPREAD';
-    const QUERY = 'QUERY';
-    const MUTATION = 'MUTATION';
-    const FRAGMENT_DEFINITION = 'FRAGMENT_DEFINITION';
-    const INPUT_OBJECT = 'INPUT_OBJECT';
-    const INLINE_FRAGMENT = 'INLINE_FRAGMENT';
-    const UNION = 'UNION';
-    const SCALAR = 'SCALAR';
-    const FIELD_DEFINITION = 'FIELD_DEFINITION';
-    const ARGUMENT_DEFINITION = 'ARGUMENT_DEFINITION';
-    const ENUM = 'ENUM';
-    const OBJECT = 'OBJECT';
-    const ENUM_VALUE = 'ENUM_VALUE';
-    const FIELD = 'FIELD';
-    const SCHEMA = 'SCHEMA';
-    const INPUT_FIELD_DEFINITION = 'INPUT_FIELD_DEFINITION';
-}
diff --git a/src/Type/Definition/ObjectType.php b/src/Type/Definition/ObjectType.php
index d77a731..717942f 100644
--- a/src/Type/Definition/ObjectType.php
+++ b/src/Type/Definition/ObjectType.php
@@ -3,7 +3,7 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Error\InvariantViolation;
 use GraphQL\Language\AST\ObjectTypeDefinitionNode;
-use GraphQL\Language\AST\TypeExtensionDefinitionNode;
+use GraphQL\Language\AST\ObjectTypeExtensionNode;
 use GraphQL\Utils\Utils;
 
 
@@ -70,7 +70,7 @@ class ObjectType extends Type implements OutputType, CompositeType
     public $astNode;
 
     /**
-     * @var TypeExtensionDefinitionNode[]
+     * @var ObjectTypeExtensionNode[]
      */
     public $extensionASTNodes;
 
diff --git a/src/Type/Introspection.php b/src/Type/Introspection.php
index 3c87a90..7326ea4 100644
--- a/src/Type/Introspection.php
+++ b/src/Type/Introspection.php
@@ -1,10 +1,9 @@
 <?php
 namespace GraphQL\Type;
 
-
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
-use GraphQL\Type\Definition\DirectiveLocation;
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Type\Definition\EnumType;
 use GraphQL\Type\Definition\FieldArgument;
 use GraphQL\Type\Definition\FieldDefinition;
@@ -602,7 +601,7 @@ EOD;
                         ],
                         'type' => [
                             'type' => Type::nonNull(self::_type()),
-                            'resolve' => function ($field) {
+                            'resolve' => function (FieldDefinition $field) {
                                 return $field->getType();
                             }
                         ],
diff --git a/src/Utils/ASTDefinitionBuilder.php b/src/Utils/ASTDefinitionBuilder.php
index ed73dd5..7649796 100644
--- a/src/Utils/ASTDefinitionBuilder.php
+++ b/src/Utils/ASTDefinitionBuilder.php
@@ -30,7 +30,6 @@ use GraphQL\Type\Definition\NonNull;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\UnionType;
-use GraphQL\Type\Introspection;
 
 class ASTDefinitionBuilder
 {
diff --git a/src/Validator/DocumentValidator.php b/src/Validator/DocumentValidator.php
index 1750c84..2b6e242 100644
--- a/src/Validator/DocumentValidator.php
+++ b/src/Validator/DocumentValidator.php
@@ -22,6 +22,7 @@ use GraphQL\Validator\Rules\AbstractValidationRule;
 use GraphQL\Validator\Rules\ArgumentsOfCorrectType;
 use GraphQL\Validator\Rules\DefaultValuesOfCorrectType;
 use GraphQL\Validator\Rules\DisableIntrospection;
+use GraphQL\Validator\Rules\ExecutableDefinitions;
 use GraphQL\Validator\Rules\FieldsOnCorrectType;
 use GraphQL\Validator\Rules\FragmentsOnCompositeTypes;
 use GraphQL\Validator\Rules\KnownArgumentNames;
@@ -122,6 +123,7 @@ class DocumentValidator
     {
         if (null === self::$defaultRules) {
             self::$defaultRules = [
+                ExecutableDefinitions::class => new ExecutableDefinitions(),
                 UniqueOperationNames::class => new UniqueOperationNames(),
                 LoneAnonymousOperation::class => new LoneAnonymousOperation(),
                 KnownTypeNames::class => new KnownTypeNames(),
diff --git a/src/Validator/Rules/ExecutableDefinitions.php b/src/Validator/Rules/ExecutableDefinitions.php
new file mode 100644
index 0000000..f512d6d
--- /dev/null
+++ b/src/Validator/Rules/ExecutableDefinitions.php
@@ -0,0 +1,47 @@
+<?php
+namespace GraphQL\Validator\Rules;
+
+use GraphQL\Error\Error;
+use GraphQL\Language\AST\DocumentNode;
+use GraphQL\Language\AST\FragmentDefinitionNode;
+use GraphQL\Language\AST\Node;
+use GraphQL\Language\AST\NodeKind;
+use GraphQL\Language\AST\OperationDefinitionNode;
+use GraphQL\Language\Visitor;
+use GraphQL\Validator\ValidationContext;
+
+/**
+ * Executable definitions
+ *
+ * A GraphQL document is only valid for execution if all definitions are either
+ * operation or fragment definitions.
+ */
+class ExecutableDefinitions extends AbstractValidationRule
+{
+    static function nonExecutableDefinitionMessage($defName)
+    {
+        return "The \"$defName\" definition is not executable.";
+    }
+
+    public function getVisitor(ValidationContext $context)
+    {
+        return [
+            NodeKind::DOCUMENT => function (DocumentNode $node) use ($context) {
+                /** @var Node $definition */
+                foreach ($node->definitions as $definition) {
+                    if (
+                        !$definition instanceof OperationDefinitionNode &&
+                        !$definition instanceof FragmentDefinitionNode
+                    ) {
+                        $context->reportError(new Error(
+                            self::nonExecutableDefinitionMessage($definition->name->value),
+                            [$definition->name]
+                        ));
+                    }
+                }
+
+                return Visitor::skipNode();
+            }
+        ];
+    }
+}
diff --git a/src/Validator/Rules/KnownDirectives.php b/src/Validator/Rules/KnownDirectives.php
index 3043cb6..9d48aa5 100644
--- a/src/Validator/Rules/KnownDirectives.php
+++ b/src/Validator/Rules/KnownDirectives.php
@@ -5,8 +5,8 @@ use GraphQL\Error\Error;
 use GraphQL\Language\AST\DirectiveNode;
 use GraphQL\Language\AST\InputObjectTypeDefinitionNode;
 use GraphQL\Language\AST\NodeKind;
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Validator\ValidationContext;
-use GraphQL\Type\Definition\DirectiveLocation;
 
 class KnownDirectives extends AbstractValidationRule
 {
@@ -37,7 +37,7 @@ class KnownDirectives extends AbstractValidationRule
                         self::unknownDirectiveMessage($node->name->value),
                         [$node]
                     ));
-                    return ;
+                    return;
                 }
                 $candidateLocation = $this->getDirectiveLocationForASTPath($ancestors);
 
@@ -73,7 +73,8 @@ class KnownDirectives extends AbstractValidationRule
             case NodeKind::FRAGMENT_DEFINITION: return DirectiveLocation::FRAGMENT_DEFINITION;
             case NodeKind::SCHEMA_DEFINITION: return DirectiveLocation::SCHEMA;
             case NodeKind::SCALAR_TYPE_DEFINITION: return DirectiveLocation::SCALAR;
-            case NodeKind::OBJECT_TYPE_DEFINITION: return DirectiveLocation::OBJECT;
+            case NodeKind::OBJECT_TYPE_DEFINITION:
+            case NodeKind::OBJECT_TYPE_EXTENSION: return DirectiveLocation::OBJECT;
             case NodeKind::FIELD_DEFINITION: return DirectiveLocation::FIELD_DEFINITION;
             case NodeKind::INTERFACE_TYPE_DEFINITION: return DirectiveLocation::IFACE;
             case NodeKind::UNION_TYPE_DEFINITION: return DirectiveLocation::UNION;
diff --git a/tests/Executor/ExecutorTest.php b/tests/Executor/ExecutorTest.php
index c38045e..bd6a16d 100644
--- a/tests/Executor/ExecutorTest.php
+++ b/tests/Executor/ExecutorTest.php
@@ -965,14 +965,14 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
     }
 
     /**
-     * @it fails to execute a query containing a type definition
+     * @it executes ignoring invalid non-executable definitions
      */
-    public function testFailsToExecuteQueryContainingTypeDefinition()
+    public function testExecutesIgnoringInvalidNonExecutableDefinitions()
     {
         $query = Parser::parse('
       { foo }
 
-      type Query { foo: String }
+      type Query { bar: String }
     ');
 
         $schema = new Schema([
@@ -988,12 +988,9 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
         $result = Executor::execute($schema, $query);
 
         $expected = [
-            'errors' => [
-                [
-                    'message' => 'GraphQL cannot execute a request containing a ObjectTypeDefinition.',
-                    'locations' => [['line' => 4, 'column' => 7]],
-                ]
-            ]
+            'data' => [
+                'foo' => null,
+            ],
         ];
 
         $this->assertArraySubset($expected, $result->toArray());
diff --git a/tests/Language/SchemaParserTest.php b/tests/Language/SchemaParserTest.php
index 81d8a3f..77e2e92 100644
--- a/tests/Language/SchemaParserTest.php
+++ b/tests/Language/SchemaParserTest.php
@@ -150,21 +150,16 @@ extend type Hello {
             'kind' => NodeKind::DOCUMENT,
             'definitions' => [
                 [
-                    'kind' => NodeKind::TYPE_EXTENSION_DEFINITION,
-                    'definition' => [
-                        'kind' => NodeKind::OBJECT_TYPE_DEFINITION,
-                        'name' => $this->nameNode('Hello', $loc(13, 18)),
-                        'interfaces' => [],
-                        'directives' => [],
-                        'fields' => [
-                            $this->fieldNode(
-                                $this->nameNode('world', $loc(23, 28)),
-                                $this->typeNode('String', $loc(30, 36)),
-                                $loc(23, 36)
-                            )
-                        ],
-                        'loc' => $loc(8, 38),
-                        'description' => null
+                    'kind' => NodeKind::OBJECT_TYPE_EXTENSION,
+                    'name' => $this->nameNode('Hello', $loc(13, 18)),
+                    'interfaces' => [],
+                    'directives' => [],
+                    'fields' => [
+                        $this->fieldNode(
+                            $this->nameNode('world', $loc(23, 28)),
+                            $this->typeNode('String', $loc(30, 36)),
+                            $loc(23, 36)
+                        )
                     ],
                     'loc' => $loc(1, 38)
                 ]
@@ -174,16 +169,59 @@ extend type Hello {
         $this->assertEquals($expected, TestUtils::nodeToArray($doc));
     }
 
+    /**
+     * @it Extension without fields
+     */
+    public function testExtensionWithoutFields()
+    {
+        $body = 'extend type Hello implements Greeting';
+        $doc = Parser::parse($body);
+        $loc = function($start, $end) {
+            return TestUtils::locArray($start, $end);
+        };
+        $expected = [
+            'kind' => NodeKind::DOCUMENT,
+            'definitions' => [
+                [
+                    'kind' => NodeKind::OBJECT_TYPE_EXTENSION,
+                    'name' => $this->nameNode('Hello', $loc(12, 17)),
+                    'interfaces' => [
+                        $this->typeNode('Greeting', $loc(29, 37)),
+                    ],
+                    'directives' => [],
+                    'fields' => [],
+                    'loc' => $loc(0, 37)
+                ]
+            ],
+            'loc' => $loc(0, 37)
+        ];
+        $this->assertEquals($expected, TestUtils::nodeToArray($doc));
+    }
+
     /**
      * @it Extension do not include descriptions
      * @expectedException \GraphQL\Error\SyntaxError
-     * @expectedExceptionMessage Syntax Error GraphQL (2:1)
+     * @expectedExceptionMessage Syntax Error GraphQL (3:7)
      */
     public function testExtensionDoNotIncludeDescriptions() {
         $body = '
-"Description"
-extend type Hello {
-    world: String
+      "Description"
+      extend type Hello {
+        world: String
+      }';
+        Parser::parse($body);
+    }
+
+    /**
+     * @it Extension do not include descriptions
+     * @expectedException \GraphQL\Error\SyntaxError
+     * @expectedExceptionMessage Syntax Error GraphQL (2:14)
+     */
+    public function testExtensionDoNotIncludeDescriptions2() {
+        $body = '
+      extend "Description" type Hello {
+        world: String
+      }
 }';
         Parser::parse($body);
     }
@@ -236,7 +274,7 @@ type Hello {
      */
     public function testSimpleTypeInheritingInterface()
     {
-        $body = 'type Hello implements World { }';
+        $body = 'type Hello implements World { field: String }';
         $loc = function($start, $end) { return TestUtils::locArray($start, $end); };
         $doc = Parser::parse($body);
 
@@ -250,12 +288,18 @@ type Hello {
                         $this->typeNode('World', $loc(22, 27))
                     ],
                     'directives' => [],
-                    'fields' => [],
-                    'loc' => $loc(0,31),
+                    'fields' => [
+                        $this->fieldNode(
+                            $this->nameNode('field', $loc(30, 35)),
+                            $this->typeNode('String', $loc(37, 43)),
+                            $loc(30, 43)
+                        )
+                    ],
+                    'loc' => $loc(0, 45),
                     'description' => null
                 ]
             ],
-            'loc' => $loc(0,31)
+            'loc' => $loc(0, 45)
         ];
 
         $this->assertEquals($expected, TestUtils::nodeToArray($doc));
@@ -266,7 +310,7 @@ type Hello {
      */
     public function testSimpleTypeInheritingMultipleInterfaces()
     {
-        $body = 'type Hello implements Wo, rld { }';
+        $body = 'type Hello implements Wo, rld { field: String }';
         $loc = function($start, $end) {return TestUtils::locArray($start, $end);};
         $doc = Parser::parse($body);
 
@@ -281,12 +325,18 @@ type Hello {
                         $this->typeNode('rld', $loc(26,29))
                     ],
                     'directives' => [],
-                    'fields' => [],
-                    'loc' => $loc(0, 33),
+                    'fields' => [
+                        $this->fieldNode(
+                            $this->nameNode('field', $loc(32, 37)),
+                            $this->typeNode('String', $loc(39, 45)),
+                            $loc(32, 45)
+                        )
+                    ],
+                    'loc' => $loc(0, 47),
                     'description' => null
                 ]
             ],
-            'loc' => $loc(0, 33)
+            'loc' => $loc(0, 47)
         ];
 
         $this->assertEquals($expected, TestUtils::nodeToArray($doc));
@@ -754,6 +804,7 @@ input Hello {
 
     /**
      * @it Simple input object with args should fail
+     * @expectedException \GraphQL\Error\SyntaxError
      */
     public function testSimpleInputObjectWithArgsShouldFail()
     {
@@ -761,7 +812,19 @@ input Hello {
 input Hello {
   world(foo: Int): String
 }';
-        $this->setExpectedException('GraphQL\Error\SyntaxError');
+        Parser::parse($body);
+    }
+
+    /**
+     * @it Directive with incorrect locations
+     * @expectedException \GraphQL\Error\SyntaxError
+     * @expectedExceptionMessage Syntax Error GraphQL (2:33) Unexpected Name "INCORRECT_LOCATION"
+     */
+    public function testDirectiveWithIncorrectLocationShouldFail()
+    {
+        $body = '
+      directive @foo on FIELD | INCORRECT_LOCATION
+';
         Parser::parse($body);
     }
 
diff --git a/tests/Language/SchemaPrinterTest.php b/tests/Language/SchemaPrinterTest.php
index 3b9a098..3141f06 100644
--- a/tests/Language/SchemaPrinterTest.php
+++ b/tests/Language/SchemaPrinterTest.php
@@ -116,9 +116,7 @@ extend type Foo {
   seven(argument: [String]): Type
 }
 
-extend type Foo @onType {}
-
-type NoFields {}
+extend type Foo @onType
 
 directive @skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
diff --git a/tests/Language/schema-kitchen-sink.graphql b/tests/Language/schema-kitchen-sink.graphql
index 4b3fbaa..016707d 100644
--- a/tests/Language/schema-kitchen-sink.graphql
+++ b/tests/Language/schema-kitchen-sink.graphql
@@ -68,9 +68,7 @@ extend type Foo {
   seven(argument: [String]): Type
 }
 
-extend type Foo @onType {}
-
-type NoFields {}
+extend type Foo @onType
 
 directive @skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
diff --git a/tests/Utils/BuildSchemaTest.php b/tests/Utils/BuildSchemaTest.php
index b77220a..6c4eaa6 100644
--- a/tests/Utils/BuildSchemaTest.php
+++ b/tests/Utils/BuildSchemaTest.php
@@ -1025,7 +1025,9 @@ schema {
   query: Hello
 }
 
-type Hello implements Bar { }
+type Hello implements Bar {
+  field: String
+}
 ';
         $doc = Parser::parse($body);
         $schema = BuildSchema::buildAST($doc);
diff --git a/tests/Validator/ExecutableDefinitionsTest.php b/tests/Validator/ExecutableDefinitionsTest.php
new file mode 100644
index 0000000..2b9eda3
--- /dev/null
+++ b/tests/Validator/ExecutableDefinitionsTest.php
@@ -0,0 +1,79 @@
+<?php
+namespace GraphQL\Tests\Validator;
+
+use GraphQL\Error\FormattedError;
+use GraphQL\Language\SourceLocation;
+use GraphQL\Validator\Rules\ExecutableDefinitions;
+use GraphQL\Validator\Rules\KnownDirectives;
+
+class ExecutableDefinitionsTest extends TestCase
+{
+    // Validate: Executable definitions
+
+    /**
+     * @it with only operation
+     */
+    public function testWithOnlyOperation()
+    {
+        $this->expectPassesRule(new ExecutableDefinitions, '
+      query Foo {
+        dog {
+          name
+        }
+      }
+        ');
+    }
+
+    /**
+     * @it with operation and fragment
+     */
+    public function testWithOperationAndFragment()
+    {
+        $this->expectPassesRule(new ExecutableDefinitions, '
+      query Foo {
+        dog {
+          name
+          ...Frag
+        }
+      }
+      
+      fragment Frag on Dog {
+        name
+      }
+        ');
+    }
+
+    /**
+     * @it with typeDefinition
+     */
+    public function testWithTypeDefinition()
+    {
+        $this->expectFailsRule(new ExecutableDefinitions, '
+      query Foo {
+        dog {
+          name
+        }
+      }
+      
+      type Cow {
+        name: String
+      }
+      
+      extend type Dog {
+        color: String
+      }
+        ',
+            [
+                $this->nonExecutableDefinition('Cow', 8, 12),
+                $this->nonExecutableDefinition('Dog', 12, 19),
+            ]);
+    }
+
+    private function nonExecutableDefinition($defName, $line, $column)
+    {
+        return FormattedError::create(
+            ExecutableDefinitions::nonExecutableDefinitionMessage($defName),
+            [ new SourceLocation($line, $column) ]
+        );
+    }
+}
diff --git a/tests/Validator/KnownDirectivesTest.php b/tests/Validator/KnownDirectivesTest.php
index d581d1c..3e7998e 100644
--- a/tests/Validator/KnownDirectivesTest.php
+++ b/tests/Validator/KnownDirectivesTest.php
@@ -136,6 +136,8 @@ class KnownDirectivesTest extends TestCase
           myField(myArg: Int @onArgumentDefinition): String @onFieldDefinition
         }
 
+        extend type MyObj @onObject
+
         scalar MyScalar @onScalar
 
         interface MyInterface @onInterface {
diff --git a/tests/Validator/TestCase.php b/tests/Validator/TestCase.php
index 4277bfc..028ac24 100644
--- a/tests/Validator/TestCase.php
+++ b/tests/Validator/TestCase.php
@@ -3,6 +3,7 @@ namespace GraphQL\Tests\Validator;
 
 use GraphQL\Language\Parser;
 use GraphQL\Type\Schema;
+use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\EnumType;
 use GraphQL\Type\Definition\InputObjectType;
@@ -259,6 +260,24 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
             ]
         ]);
 
+        $invalidScalar = new CustomScalarType([
+            'name' => 'Invalid',
+            'serialize' => function ($value) { return $value; },
+            'parseLiteral' => function ($node) {
+                throw new \Exception('Invalid scalar is always invalid: ' . $node->value);
+            },
+            'parseValue' => function ($value) {
+                throw new \Exception('Invalid scalar is always invalid: ' . $value);
+            },
+        ]);
+
+        $anyScalar = new CustomScalarType([
+            'name' => 'Any',
+            'serialize' => function ($value) { return $value; },
+            'parseLiteral' => function ($node) { return $node; }, // Allows any value
+            'parseValue' => function ($value) { return $value; }, // Allows any value
+        ]);
+
         $queryRoot = new ObjectType([
             'name' => 'QueryRoot',
             'fields' => [
@@ -274,6 +293,14 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
                 'dogOrHuman' => ['type' => $DogOrHuman],
                 'humanOrAlien' => ['type' => $HumanOrAlien],
                 'complicatedArgs' => ['type' => $ComplicatedArgs],
+                'invalidArg' => [
+                    'args' => ['arg' => ['type' => $invalidScalar]],
+                    'type' => Type::string(),
+                ],
+                'anyArg' => [
+                    'args' => ['arg' => ['type' => $anyScalar]],
+                    'type' => Type::string(),
+                ],
             ]
         ]);
 
diff --git a/tools/gendocs.php b/tools/gendocs.php
index 7a2d16c..95b5b96 100644
--- a/tools/gendocs.php
+++ b/tools/gendocs.php
@@ -9,7 +9,7 @@ $entries = [
     \GraphQL\GraphQL::class,
     \GraphQL\Type\Definition\Type::class,
     \GraphQL\Type\Definition\ResolveInfo::class,
-    \GraphQL\Type\Definition\DirectiveLocation::class => ['constants' => true],
+    \GraphQL\Language\DirectiveLocation::class => ['constants' => true],
     \GraphQL\Type\SchemaConfig::class,
     \GraphQL\Type\Schema::class,
     \GraphQL\Language\Parser::class,