Bug 18091 – "Error instantiating" cumulativeFold when passing a function inside another function

DMD64 D Compiler v2.072.1 Best see with a test case: import std.algorithm : cumulativeFold; struct T {} T t1(T a, int b) { return T.init; } void main() { auto arr = [0,1,1,0,0,0]; T t2(T a, int b) { return T.init; } auto r1 = arr.cumulativeFold!( (a,b) => T.init )( T.init ); // no error auto r2 = arr.cumulativeFold!t1( T.init ); // no error //auto r3 = arr.cumulativeFold!t2( T.init ); // errors }

This is an issue with delegates: /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/iteration.d(3377): Error: constructor onlineapp.main.cumulativeFold!(t2).cumulativeFoldImpl!(int[], T).cumulativeFoldImpl.Result.this cannot access frame of function D main /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/iteration.d(3412): Error: function onlineapp.main.cumulativeFold!(t2).cumulativeFoldImpl!(int[], T).cumulativeFoldImpl.Result.popFront cannot access frame of function D main /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/iteration.d(3336): Error: template instance onlineapp.main.cumulativeFold!(t2).cumulativeFoldImpl!(int[], T) error instantiating onlineapp.d(19): instantiated from here: cumulativeFold!(int[], T) Run: https://run.dlang.io/is/fh0WCC

With the help of dustmite I got this down to: template foo(T...) { static void bar() { T[0]; } } void main() { void t() {} foo!t(); } Don't know, if this helps anybody... The variadic argument seems to matter somehow.

*** This issue has been marked as a duplicate of issue 17841 ***