Why doesn't `opAssign` work for my templated struct?

[Nick Treleaven]

On Saturday, 9 November 2024 at 12:33:44 UTC, Nick Treleaven 
wrote:
> On Friday, 8 November 2024 at 21:55:53 UTC, Liam McGillivray 
> wrote:
>>	Milligrams mass = Milligrams(20f);
>
> I'm not sure why that compiles.

Filed: https://issues.dlang.org/show_bug.cgi?id=24850