src/Parser/Ast/ArgumentValue/Variable.php
public function getValue()
    {
        if (null === $this->value) {
            if ($this->hasDefaultValue()) {
                return $this->defaultValue;
            }
            throw new \LogicException('Value is not set for variable "' . $this->name . '"');
        }

        return $this->value;
    }
public function getValue()
    {
        if (null === $this->value) {
            if ($this->hasDefaultValue()) {
                return $this->defaultValue;
            }
            throw new \LogicException('Value is not set for variable "' . $this->name . '"');
        }

        return $this->value;
    }
@return mixed

@throws \LogicException