Bug 16018 – fold size_t[] with int seed causes forward reference error

% cat test.d import std.algorithm; void foo(size_t[] shape) { shape[].fold!"a*b"(1); } % dmd test.d std/traits.d(551): Error: forward reference of variable parentPrefix std/traits.d(461): Error: template instance std.traits.fqnSym!(binaryFun) error instantiating std/algorithm/iteration.d(2680): instantiated from here: fullyQualifiedName!(binaryFun) std/algorithm/iteration.d(2661): instantiated from here: reduceImpl!(false, ulong[], int) std/algorithm/iteration.d(2645): instantiated from here: reducePreImpl!(ulong[], int) std/algorithm/iteration.d(3024): instantiated from here: reduce!(int, ulong[]) test.d(4): instantiated from here: fold!(ulong[], int) std/algorithm/iteration.d(2677): Error: static assert __error std/algorithm/iteration.d(2661): instantiated from here: reduceImpl!(false, ulong[], int) std/algorithm/iteration.d(2645): instantiated from here: reducePreImpl!(ulong[], int) std/algorithm/iteration.d(3024): instantiated from here: reduce!(int, ulong[]) test.d(4): instantiated from here: fold!(ulong[], int) works fine if you replace 1 with size_t(1)

Meanwhile the example produces a static assert error: Error: static assert: "Incompatible function/seed/element: binaryFun/int/ulong" The type of the seed defines the type of the result, here: int, but the elements of the range are of type size_t, which is ulong on 64bit computers. As int * ulong results in a ulong, which cannot implicitly be casted to int, this results in an error. The example works, when 1 is replaced by 1L or size_t.init