TEMPLATE_TEST_CASE: "duplicate type detected" should not be an error (allow duplicate types)

[VioletGiraffe]

"Duplicate type" is a very inconvenient error as it will make some simple test cases require a lot of boilerplate code to circumvent this compile-time check. The thing is that certain types may or may not be synonymous depending on the current platform, and when writing cross-platform code, one may just want to list all imaginable types. Sure, the test case may run twice for the same actual type, but so what?

Example: size_t may be a synonym for unsigned long - then size_t is incompatible with unsigned long long, or it could be vice versa. I wanted to simply list all three (size_t, unsigned long, unsigned long long) and I got this compilation error.

[horenmar]

That is a good point we did not consider.