• Prateek Nayak (8/8) Aug 10 2019 A nested function can be passed to another function evident from
• Alex (7/15) Aug 10 2019 The part I'm not sure about:
• aliak (15/23) Aug 10 2019 This looks like it could be a bug to me. If you explicitly

Prateek Nayak <lelouch.cpp gmail.com> writes:

A nested function can be passed to another function evident from 
this example: https://run.dlang.io/is/6waRkB

However if the nested function is a template function, it raises 
an error
https://run.dlang.io/is/PQhkwl
The error being: cannot get frame pointer to the nested function

Is there a way to pass a nested template function to a function 
declared outside the outer function scope?

Alex <sascha.orlov gmail.com> writes:

On Saturday, 10 August 2019 at 17:45:43 UTC, Prateek Nayak wrote:
 A nested function can be passed to another function evident 
 from this example: https://run.dlang.io/is/6waRkB

 However if the nested function is a template function, it 
 raises an error
 https://run.dlang.io/is/PQhkwl
 The error being: cannot get frame pointer to the nested function

 Is there a way to pass a nested template function to a function 
 declared outside the outer function scope?

The part I'm not sure about:
This is not possible: Before instantiation, the object does not 
exist, you cannot, therefore, pass its pointer, not to speak 
about the pointer of its frame.

However, how about this:
https://run.dlang.io/is/8drZRf

aliak <something something.com> writes:

On Saturday, 10 August 2019 at 17:45:43 UTC, Prateek Nayak wrote:
 A nested function can be passed to another function evident 
 from this example: https://run.dlang.io/is/6waRkB

 However if the nested function is a template function, it 
 raises an error
 https://run.dlang.io/is/PQhkwl
 The error being: cannot get frame pointer to the nested function

 Is there a way to pass a nested template function to a function 
 declared outside the outer function scope?

This looks like it could be a bug to me. If you explicitly 
instantiate the nested template and call dispatch like 
dispatch!(nested!0) then it works.

An alias template parameter can accept both a template and an 
instantiated template. I.e.

template X(T) {}
alias A = X; // ok
alias B = X!int; // ok

So it's unclear what should happen. At the least, the defaulted 
argument should be applied at the call site (Func(a)).

Note though that neither versions will work on ldc or gdc 
however. Because there's a bug [0] that has only been fixed in 
for dmd.

[0] https://github.com/dlang/dmd/pull/9282