KeyRemap4MacBook setting to complete pending close-parens/quotes/brackets, insert semicolon, enter.

private.xml

<?xml version="1.0"?>
<root>
    <item>
        <name>- XCode Custom Keys -</name>
        <item>
            <name>Fn+Return completes line with semicolon only in XCode</name>
            <identifier>private.xcode.completeline</identifier>
            <only>XCODE</only>
            <autogen>
                --KeyToKey--
                KeyCode::RETURN, ModifierFlag::FN | ModifierFlag::NONE,
                KeyCode::E, ModifierFlag::CONTROL_L, KeyCode::SEMICOLON, KeyCode::RETURN
            </autogen>
        </item>
    </item>
</root>

Add the inner <item> block somewhere in your Private.xml from KeyRemap4MacBook https://github.com/tekezo/KeyRemap4MacBook