Unexpected issue with std.format

[Saurabh Das]

On Saturday, 1 February 2020 at 13:39:34 UTC, Saurabh Das wrote:
> I faced this issue while working with custom formatting for a 
> struct. I have reduced the error down to this test program:
>
> [...]

PS: Currently using DMD64 D Compiler v2.090.0