[fpc-pascal] Caller agnostic procedure variables

[Michael Van Canneyt]

On Tue, 15 Feb 2022, Ryan Joseph via fpc-pascal wrote:

>
>
>> On Feb 15, 2022, at 8:26 PM, Sven Barth via fpc-pascal <fpc-pascal at lists.freepascal.org> wrote:
>> 
>> It's relatively "easy" to implement assigning a nested function to function references. However assigning a nested function variable to a function reference is much harder.
>> Assigning a function reference to a nested function variable is hard as well. 
>> 
>
> I'm getting lost with the terms now I think. 
> If your function takes a function reference parameter and you assign it a nested function  pointer, 
> this is difficult? I believe this was Michaels request in that code snippet.

Sven will need to confirm, but as I understand it:

Procedure DoDemo(aTest : TProc);

Procedure MyTest;

   Procedure DoSub;
   begin
   end;

begin
   DoDemo(DoSub)
end;

is easy.

but

Procedure DoDemo(aTest : TProc);

Procedure MyTest;

Var
   ASub : procedure is nested;

begin
   aSub:=SomeFunctionThatReturnsANestedProc;
   DoDemo(aSub);
end;

is difficult.

Michael.