Validate interface implemented ancestors

Part of the work done to implement interfaces implementing interfaces.
This was caught by test and improves on the previously done changes for
the SchemaValidationContext by implementing
`validateTypeImplementsAncestors` which was missing.

Author: Kingdutch

src/Type/SchemaValidationContext.php

@@ -307,7 +307,7 @@ public function validateTypes() : void
                 $this->validateFields($type);
 
                 // Ensure objects implement the interfaces they claim to.
-                $this->validateTypeInterfaces($type);
+                $this->validateInterfaces($type);
 
                 // Ensure directives are valid
                 $this->validateDirectivesAtLocation(
@@ -319,7 +319,7 @@ public function validateTypes() : void
                 $this->validateFields($type);
 
                 // Ensure interfaces implement the interfaces they claim to.
-                $this->validateTypeInterfaces($type);
+                $this->validateInterfaces($type);
 
                 // Ensure directives are valid
                 $this->validateDirectivesAtLocation(
@@ -661,9 +661,9 @@ private function getFieldArgNode($type, $fieldName, $argName)
     /**
      * @param ObjectType|InterfaceType $type
      */
-    private function validateTypeInterfaces(ImplementingType $type)
+    private function validateInterfaces(ImplementingType $type)
     {
-        $implementedTypeNames = [];
+        $ifaceTypeNames = [];
         foreach ($type->getInterfaces() as $iface) {
             if (! $iface instanceof InterfaceType) {
                 $this->reportError(
@@ -676,14 +676,16 @@ private function validateTypeInterfaces(ImplementingType $type)
                 );
                 continue;
             }
-            if (isset($implementedTypeNames[$iface->name])) {
+            if (isset($ifaceTypeNames[$iface->name])) {
                 $this->reportError(
                     sprintf('Type %s can only implement %s once.', $type->name, $iface->name),
                     $this->getAllImplementsInterfaceNodes($type, $iface)
                 );
                 continue;
             }
-            $implementedTypeNames[$iface->name] = true;
+            $ifaceTypeNames[$iface->name] = true;
+
+            $this->validateTypeImplementsAncestors($type, $iface);
             $this->validateTypeImplementsInterface($type, $iface);
         }
     }
@@ -877,6 +879,36 @@ private function validateTypeImplementsInterface($type, $iface)
         }
     }
 
+    /**
+     * @param ObjectType|InterfaceType $type
+     * @param InterfaceType            $iface
+     */
+    private function validateTypeImplementsAncestors(ImplementingType $type, $iface) {
+        $typeInterfaces = $type->getInterfaces();
+        foreach ($iface->getInterfaces() as $transitive) {
+            if (!in_array($transitive, $typeInterfaces)) {
+                $this->reportError(
+                    $transitive === $type ?
+                        sprintf(
+                            "Type %s cannot implement %s because it would create a circular reference.",
+                            $type->name,
+                            $iface->name
+                        ) :
+                        sprintf(
+                            "Type %s must implement %s because it is implemented by %s.",
+                            $type->name,
+                            $transitive->name,
+                            $iface->name
+                        ),
+                    array_merge(
+                        $this->getAllImplementsInterfaceNodes($iface, $transitive),
+                        $this->getAllImplementsInterfaceNodes($type, $iface)
+                    )
+                );
+            }
+        }
+    }
+
     private function validateUnionMembers(UnionType $union)
     {
         $memberTypes = $union->getTypes();