Crystal: Can't use splat generics in Proc type declaration for instance variable

[Blacksmoke16]

See https://forum.crystal-lang.org/t/splat-generics-with-proc/1410

class Foo(R, *A)
  def initialize(@action : Proc(*A, R)); end
end


pp Foo(String, Int32, Bool).new ->(a : Int32, b : Bool) { "foo" }

Error:

Error: instance variable '@action' of Foo(String, Int32, Bool) must be Proc(*A, String), not Proc(Int32, Bool, String)

[Blacksmoke16]

@asterite Do you have any pointers on where to look if I wanted to take a shot at this? My current guess is that the splat arguments need to be "expanded" before seeing if they match or not?

[Blacksmoke16]

Update, this is also an issue when using splat generics as type restriction of a method within Union.

https://play.crystal-lang.org/#/r/85x2

class Foo(*Args)
  def execute(value : Union(*Args))
    pp value
  end
end


foo = Foo(String, Int32).new

foo.execute 19

Showing last frame. Use --error-trace for full trace.

error in line 10
Error: no overload matches 'Foo(String, Int32)#execute' with type Int32

Overloads are:
 - Foo(Args)#execute(value : Union(*Args))

[asterite]

I think the logic is in restrictions.cr but I'm not sure.