Start a new namespace.
This also resets the alias table.
Name|null $namespace Null is the global namespace:
public function startNamespace(?Name $namespace = null) : void { $this->namespace = $namespace; $this->origAliases = $this->aliases = [ Stmt\Use_::TYPE_NORMAL => [], Stmt\Use_::TYPE_FUNCTION => [], Stmt\Use_::TYPE_CONSTANT => [], ]; }