[BUG] Compiler error when storing function whose input/output types are parameterized in struct

[Brian-M-J]

Bug description

When running the code snippet below, I get the following compiler error:

/source/prog.mojo:14:37: error: invalid initialization: argument #1 cannot be converted from 'fn(num: Int) -> String' to 'fn(Int) -> String'
    var a = FuncyStruct[Int, String](convert)
            ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
/source/prog.mojo:2:8: note: function declared here
struct FuncyStruct[I: AnyType, O: AnyType]:
       ^
mojo: error: failed to parse the provided Mojo source module

I was expecting the code to work fine and print 16. The compiler seems to consider the argument name as part of the type of the function. That's just an implementation detail and shouldn't be important to it.

Steps to reproduce

Run the following code to reproduce the error:

@value
struct FuncyStruct[I: AnyType, O: AnyType]:
    var func: fn (I) -> O
 
    fn apply(self, in_: I) -> O:
        return self.func(in_)
 
 
fn convert(num: Int) -> String:
    return str(num + 10)
 
 
fn main():
    var a = FuncyStruct[Int, String](convert)
    print(a.apply(6))
 

System information

The Mojo Playground as of 22-05-2024.