All interface members must now be public

lib/interface.js

@@ -236,6 +236,14 @@ var extend = ( function( extending )
                     );
                 }
 
+                // all members must be public
+                if ( keywords[ 'protected' ] || keywords[ 'private' ] )
+                {
+                    throw TypeError(
+                        iname + " member " + name + " must be public"
+                    );
+                }
+
                 member_builder.buildMethod(
                     members, null, name, value, keywords
                 );

test/test-interface-extend.js

@@ -205,3 +205,29 @@ for ( var i = 0; i < base_types.length; i++ )
     }
 } )();
 
+
+/**
+ * Interfaces represent a public API that must be implemented. It does not make
+ * sense to have members be anything but public.
+ */
+( function testInterfaceMembersMustBePublic()
+{
+    // protected
+    assert.throws( function()
+    {
+        Interface(
+        {
+            'abstract protected foo': [],
+        } );
+    }, Error, "Interface members must be public (1)" );
+
+    // private
+    assert.throws( function()
+    {
+        Interface(
+        {
+            'abstract private foo': [],
+        } );
+    }, Error, "Interface members must be public (2)" );
+} )();
+