Don't show Ambiguous class resolution warning if class when not ambiguous

if a class or interface is defined twice in the same class, this should not produce a warning

tests/Composer/Test/Autoload/ClassMapGeneratorTest.php

@@ -133,6 +133,27 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
         $this->assertTrue(in_array($msg, $messages, true), $msg.' not found in expected messages ('.var_export($messages, true).')');
     }
 
+    /**
+     * If one file has a class or interface defined more than once,
+     * an ambiguous reference warning should not be produced
+     */
+    public function testUnambiguousReference()
+    {
+        $this->checkIfFinderIsAvailable();
+
+        $finder = new Finder();
+        $finder->files()->in(__DIR__ . '/Fixtures/Unambiguous');
+
+        $io = $this->getMockBuilder('Composer\IO\ConsoleIO')
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $io->expects($this->never())
+            ->method('write');
+
+        ClassMapGenerator::createMap($finder, null, $io);
+    }
+
     /**
      * @expectedException \RuntimeException
      * @expectedExceptionMessage Could not scan for classes inside