[Issue 12811] GC-allocated closure for calling instance function in filter

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12811

--- Comment #2 from bearophile_h...@eml.cc ---
(In reply to Kenji Hara from comment #1)

 'filter' will lazily evaluate the given array outside of the 'spam'
 function, so the lambda 'i = bar(i)' needs to capture 'this' variable to
 call member function 'bar'.
 
 It will make a closure allocation.

Thank you for the answer. We'll have to add some escape analysis to turn some
closure heap allocations into stack allocations.

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[Issue 12811] GC-allocated closure for calling instance function in filter

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12811

Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |INVALID

--- Comment #1 from Kenji Hara k.hara...@gmail.com ---
(In reply to bearophile_hugs from comment #0)
 import std.algorithm: filter;
 struct Foo {
 bool bar(in int) @nogc {
 return true;
 }
 auto spam() @nogc {
 immutable static data = [1, 2];
 return data.filter!(i = bar(i));

'filter' will lazily evaluate the given array outside of the 'spam' function,
so the lambda 'i = bar(i)' needs to capture 'this' variable to call member
function 'bar'.

It will make a closure allocation.

 This gives a similar error:
 
 import std.algorithm: filter;
 struct Foo {
 bool bar(in int) @nogc {
 return true;
 }
 auto spam() @nogc {
 immutable static data = [1, 2];
 scope immutable f = (int i) = bar(i);
 return data.filter!f;

To access the delegate variable f later, 'filter' should capture the function
frame of 'spam' (and it will indirectly capture the 'this' of 'spam' function).
It will need a closure allocation.

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