Re: How to check that function gets ref parameter?

[Basile B. via Digitalmars-d-learn]

On Sunday, 13 December 2020 at 16:41:06 UTC, Andrey Zherikov 
wrote:
I'm trying to check that function has 'ref' parameter. The only 
way I found so far is to use std.traits.Parameters.

Here is the code I have:
    void f(int) {}
    void g(ref int) {}
    void main()
    {
        writeln(Parameters!f[0].stringof);
        writeln(__traits(isRef, Parameters!f[0]));
        writeln(Parameters!g.stringof);
        writeln(Parameters!g[0].stringof);
        writeln(__traits(isRef, Parameters!g[0]));
    }
The output is:
    int
    false
    (ref int)
    int
    false

"Parameters!g[0]" strips off 'ref' qualifier as you can see. 
How can I make it work?

You use the wrong traits, try ParameterStorageClassTuple instead:

  void f(int) {}
  void g(ref int) {}
  import std.traits : ParameterStorageClass, 
ParameterStorageClassTuple;
  static assert(ParameterStorageClassTuple!g[0] == 
ParameterStorageClass.ref_);
  static assert(ParameterStorageClassTuple!f[0] != 
ParameterStorageClass.ref_);