Pinq\Analysis\ITypeSystem::getFunction PHP Method

    public function getFunction($name);

 public function visitFunctionCall(O\FunctionCallExpression $expression)
 {
     $nameExpression = $expression->getName();
     $this->walk($nameExpression);
     $this->walkAll($expression->getArguments());
     if ($nameExpression instanceof O\ValueExpression) {
         $function = $this->typeSystem->getFunction($nameExpression->getValue());
         $this->metadata[$expression] = $function;
         $this->analysis[$expression] = $function->getReturnType();
     } else {
         throw new TypeException('Invalid function expression: dynamic function calls are not allowed');
     }
 }