Add Identifier::isVirtual() method

Author: Kirill Nesmeyanov

src/Node/Identifier.php

@@ -55,6 +55,20 @@ public function __construct(string $value)
         ));
     }
 
+    /**
+     * Returns {@see true} if the identifier contains the name of
+     * a "virtual" type, i.e. invalid in the PHP namespace.
+     *
+     * - `SomeClass` - Non-virtual, can be a type in PHP.
+     * - `false` - Non-virtual, can be a type in PHP.
+     * - `non-empty-array` - Virtual, cannot be defined in PHP.
+     * - `empty-string` - Virtual, cannot be defined in PHP.
+     */
+    public function isVirtual(): bool
+    {
+        return \str_contains($this->value, '-');
+    }
+
     /**
      * Returns {@see true} in case of name contains special class reference.
      */