From b321610cc72007b3990a86e7b1fe8b67ef03fee8 Mon Sep 17 00:00:00 2001
From: Mike Gerwitz <mike@mikegerwitz.com>
Date: Sat, 5 Mar 2011 21:46:44 -0500
Subject: [PATCH] Interface name included in instantiation error, if available

---
 lib/interface.js            | 11 ++++++++---
 test/test-interface-name.js | 23 +++++++++++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/lib/interface.js b/lib/interface.js
index 47051d0..d42df51 100644
--- a/lib/interface.js
+++ b/lib/interface.js
@@ -197,7 +197,7 @@ var extend = ( function( extending )
         // sanity check
         inheritCheck( prototype );
 
-        var new_interface = createInterface();
+        var new_interface = createInterface( iname );
 
         util.propParse( props, {
             property: function()
@@ -261,9 +261,11 @@ var extend = ( function( extending )
     /**
      * Creates a new interface constructor function
      *
+     * @param  {string=}  iname  interface name
+     *
      * @return  {function()}
      */
-    function createInterface()
+    function createInterface( iname )
     {
         return function()
         {
@@ -273,7 +275,10 @@ var extend = ( function( extending )
             {
                 // only called if someone tries to create a new instance of an
                 // interface
-                throw Error( "Interfaces cannot be instantiated" );
+                throw Error(
+                    "Interface" + ( ( iname ) ? ( iname + ' ' ) : '' ) +
+                        " cannot be instantiated"
+                );
             }
         };
     }
diff --git a/test/test-interface-name.js b/test/test-interface-name.js
index a50f101..dad582c 100644
--- a/test/test-interface-name.js
+++ b/test/test-interface-name.js
@@ -218,3 +218,26 @@ var common     = require( './common' ),
     }
 } )();
 
+
+( function testInterfaceNameIsIncludedInInstantiationError()
+{
+    var name = 'Foo';
+
+    try
+    {
+        // this should throw an exception (cannot instantiate interfaces)
+        Interface( name )();
+
+        // we should never get here
+        assert.fail( "Exception expected. There's a bug somewhere." );
+    }
+    catch ( e )
+    {
+        assert.notEqual(
+            e.toString().match( name ),
+            null,
+            "Interface name is included in instantiation error message"
+        );
+    }
+} )();
+