Postmortem: Template unittests are bad & you shouldn't catch Error

[Jacob Carlborg]

On Thursday, 22 October 2020 at 16:18:14 UTC, H. S. Teoh wrote:

> 	template MyTemplate(T)
> 	{
> 		auto myFunc(...) { ... }
>
> 		/// This is instantiated once per template instantiation
> 		unittest {
> 			pragma(msg, T.stringof);
> 		}
>
> 		/// This is instantiated only once, ever
> 		/// (The use of 'static' is hypothetical syntax, it can
> 		/// be anything else that marks the unittest as
> 		/// single-instance)
> 		static unittest {
> 			//pragma(msg, T.stringof); // Error: cannot reference T here
>
> 			// Have to explicitly instantiate the template
> 			// with the arguments you want to test for
> 			alias U = MyTemplate!int;
> 		}
> 	}

Might be a bit confusing when the unit test is inside a templated 
class. Because the unit test function is already static, relative 
to the class.

--
/Jacob Carlborg