Allow dist installs for dev packages that do not have a source setup

src/Composer/Downloader/DownloadManager.php

@@ -147,12 +147,10 @@ class DownloadManager
         $sourceType   = $package->getSourceType();
         $distType     = $package->getDistType();
 
-        if ((!$package->isDev() || $this->preferDist) && !($preferSource && $sourceType) && $distType) {
+        if ((!$package->isDev() || $this->preferDist || !$sourceType) && !($preferSource && $sourceType) && $distType) {
             $package->setInstallationSource('dist');
         } elseif ($sourceType) {
             $package->setInstallationSource('source');
-        } elseif ($package->isDev() && $distType) {
-            throw new \InvalidArgumentException('Dev package '.$package.' should have a source specified because for dev packages dist is used only with --prefer-dist option');
         } else {
             throw new \InvalidArgumentException('Package '.$package.' must have a source or dist specified');
         }