Crystal::Macros::Arg#restriction method always returns Nop

[mjblack]

Bug Report

Crystal::Macros::Arg#restriction always returns Nop even if there is an ASTNode. I have tested this on Crystal version 1.12.2 on MacOS Sonoma. It was also tested by @Blacksmoke16 with Crystal master branch and the issue still exists.

The issue also exists for Crystal::Macros::FunDef#return_type.

lib MyLib
  type Int = LibC::Int

  fun foo(foo : LibC::Int) : Void
end

{% MyLib.methods.first.args.each { |t| pp t; pp t.restriction.class_name } %}
{% pp MyLib.methods.first.return_type.class_name %}
# => "foo"
# => "Nop"
# => "Nop"

[Blacksmoke16]

I looked more into this the other day, and basically came to the conclusion that this is somewhat of expected behavior as part of #12848

Note: lib types won't be solved at the top-level because that happens later on. The reason for that is to not require forward declarations. But I think that even without resolved types this is useful.

As such this is more likely a feature request/enhancement than a bug.