PHPStan\Analyser\Scope::hasVariableType PHP Method

    public function hasVariableType(string $variableName) : bool
    {
        return isset($this->variableTypes[$variableName]);
    }

 /**
  * @param \PhpParser\Node\Expr\ClosureUse $node
  * @param \PHPStan\Analyser\Scope $scope
  * @return string[]
  */
 public function processNode(Node $node, Scope $scope) : array
 {
     if ($node->byRef) {
         return [];
     }
     if (!$scope->hasVariableType($node->var)) {
         return [sprintf('Undefined variable: $%s', $node->var)];
     }
     return [];
 }