Improve error reporting for RULE_PACKAGE_ALIAS

src/Composer/DependencyResolver/Rule.php

@@ -288,7 +288,10 @@ abstract class Rule
 
                 return 'Conclusion: '.$ruleText.$learnedString;
             case self::RULE_PACKAGE_ALIAS:
-                return $ruleText;
+                $aliasPackage = $this->deduplicateMasterAlias($pool->literalToPackage($literals[0]));
+                $package = $this->deduplicateMasterAlias($pool->literalToPackage($literals[1]));
+
+                return $aliasPackage->getPrettyString() .' is an alias of '.$package->getPrettyString().' and thus requires it to be installed too.';
             default:
                 return '('.$ruleText.')';
         }

tests/Composer/Test/Fixtures/installer/github-issues-8902.test

@@ -35,7 +35,7 @@ Your requirements could not be resolved to an installable set of packages.
   Problem 1
     - Root composer.json requires beyondcode/laravel-dump-server ^1.3 -> satisfiable by beyondcode/laravel-dump-server[1.4.0].
     - You can only install one version of a package, so only one of these can be installed: symfony/var-dumper[dev-master, 4.4.0].
-    - don't install symfony/var-dumper 5.2.x-dev|install symfony/var-dumper dev-master
+    - symfony/var-dumper 5.2.x-dev is an alias of symfony/var-dumper dev-master and thus requires it to be installed too.
     - laravel/framework 6.8.14 requires symfony/var-dumper ^4.3.4 -> satisfiable by symfony/var-dumper[4.4.0].
     - beyondcode/laravel-dump-server 1.4.0 requires symfony/var-dumper ^5.0 -> satisfiable by symfony/var-dumper[5.2.x-dev (alias of dev-master)].
     - Root composer.json requires laravel/framework ^6.8 -> satisfiable by laravel/framework[6.8.14].