Don't try to parse aliases versions which doesn't contain exact version

.gitignore

@@ -1,3 +1,4 @@
 vendor/
 .php_cs.cache
 composer.lock
+.idea

src/VersionParser.php

@@ -106,6 +106,13 @@ public function normalize($version, $fullVersion = null)
             $fullVersion = $version;
         }
 
+	    if (preg_match('{^(\^[^,\s]++) ++as ++([^,\s\^]++)$}', $version, $match) ||
+	        preg_match('{^([^,\s]++) ++as ++(\^[^,\s\^]++)$}', $version, $match) ||
+	        preg_match('{^([^,\s]++) ++as ++(\~[^,\s\^]++)$}', $version, $match) ||
+	        preg_match('{^(\~[^,\s]++) ++as ++([^,\s\^]++)$}', $version, $match)) {
+		    throw new \UnexpectedValueException('the alias must be an exact version');
+	    }
+
         // strip off aliasing
         if (preg_match('{^([^,\s]++) ++as ++([^,\s]++)$}', $version, $match)) {
             $version = $match[1];

tests/VersionParserTest.php

@@ -123,6 +123,10 @@ public function failingNormalizedVersions()
             'non-dev arbitrary' => array('feature-foo'),
             'metadata w/ space' => array('1.0.0+foo bar'),
             'maven style release' => array('1.0.1-SNAPSHOT'),
+            'Alias and caret on left side' => array('^1.0.0+foo as 2.0'),
+            'Alias and caret on right side' => array('1.0.0+foo as ^2.0'),
+            'Alias and tilde on left side' => array('~1.0.0+foo as 2.0'),
+            'Alias and tilde on right side' => array('1.0.0+foo as ~2.0'),
         );
     }