Bug 785472 - The Web IDL parser should not allow inheriting from an interface that is only forward declared; r=khuey

dom/bindings/parser/WebIDL.py

@@ -422,6 +422,12 @@ class IDLInterface(IDLObjectWithScope):
 
         assert not self.parent or isinstance(self.parent, IDLIdentifierPlaceholder)
         parent = self.parent.finish(scope) if self.parent else None
+        if parent and isinstance(parent, IDLExternalInterface):
+            raise WebIDLError("%s inherits from %s which does not have "
+                              "a definition" %
+                              (self.identifier.name,
+                               self.parent.identifier.name),
+                              [self.location])
         assert not parent or isinstance(parent, IDLInterface)
 
         self.parent = parent

dom/bindings/parser/tests/test_interface.py

@@ -173,3 +173,16 @@ def WebIDLTest(parser, harness):
         threw = True
 
     harness.ok(threw, "Should not allow indirectly inheriting from an interface that indirectly implements us")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            interface A;
+            interface B : A {};
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should not allow inheriting from an interface that is only forward declared")