Support for named trait class extending

We can call this a bugfix...it's more of a neglected feature that's
otherwise completely inconsistent with the rest of the system. :)

* lib/Trait.js (createNamedTrait): Support base.
  (_createStaging) [extend]: Support base.

* test/Trait/NamedTest.js: Add test.

lib/Trait.js

@@ -62,12 +62,13 @@ function Trait()
 /**
  * Create a named trait
  *
- * @param  {string}  name  trait name
- * @param  {Object}  def   trait definition
+ * @param  {string}   name  trait name
+ * @param  {Object}   dfn   trait definition
+ * @param  {Object=}  base  extension base
  *
  * @return  {Function}  named trait
  */
-function createNamedTrait( name, dfn )
+function createNamedTrait( name, dfn, base )
 {
     if ( typeof name !== 'string' )
     {
@@ -77,16 +78,26 @@ function createNamedTrait( name, dfn )
     }
 
     dfn.__name = name;
-    return Trait.extend( dfn );
+
+    var args = [ dfn ];
+    if ( base !== undefined )
+    {
+        args.unshift( base );
+    }
+
+    return Trait.extend.apply( null, args );
 }
 
 
 function _createStaging( name )
 {
     return {
-        extend: function( dfn )
+        extend: function( /*...*/ )
         {
-            return createNamedTrait( name, dfn );
+            // [base, ]dfn
+            return ( arguments.length === 1 )
+                ? createNamedTrait( name, arguments[ 0 ] )
+                : createNamedTrait( name, arguments[ 1 ], arguments[ 0 ] );
         },
 
         implement: function()

test/Trait/NamedTest.js

@@ -1,7 +1,7 @@
 /**
  * Tests named trait definitions
  *
- *  Copyright (C) 2014 Free Software Foundation, Inc.
+ *  Copyright (C) 2014, 2016 Free Software Foundation, Inc.
  *
  *  This file is part of GNU ease.js.
  *
@@ -167,4 +167,48 @@ require( 'common' ).testCase(
         // ensure that trait was properly named
         this.assertOk( T.toString().match( name ) );
     },
+
+
+    /**
+     * The extend method on the named staging object should work just as
+     * Trait.extend.
+     */
+    'Can extend class using named trait staging object': function()
+    {
+        var Sut      = this.Sut,
+            name     = "Extended",
+            expected = {},
+            T        = null;
+
+        var C = this.Class(
+        {
+            _foo: null,
+
+            getFoo: function() { return expected; },
+        } );
+
+        this.assertDoesNotThrow( function()
+        {
+            T = Sut( name )
+                .extend( C,
+                {
+                    get: function() { return this.getFoo(); },
+                } );
+        } );
+
+        // should be okay if properly extended
+        this.assertStrictEqual(
+            expected,
+            C.use( T )().get()
+        );
+
+        // should _not_ be
+        this.assertThrows( function()
+        {
+            this.Class.use( T )();
+        } );
+
+        // ensure that trait was properly named
+        this.assertOk( T.toString().match( name ) );
+    },
 } );