Feature Request: STATIC_REQUIRE macro

[parnmatt]

I've just starting using Catch2, and find it very expressive.

There are some tests that can be done at compile time; for example I am writing an adapter library and need to test if two types are implicitly convertible.

I could use REQUIRE(std::is_convertible_v<A, B>); which fits in nicely with this test framework.
However the argument is known at compile time. I've found myself doing something like:

static_assert(std::is_convertible_v<A, B>, "A should be convertible to B");
SUCCEED("A and B are convertible");

Such that the static test is logged and documented, but done at compile time.

Could there be a macro be included to wrap around that?

#define STATIC_REQUIRE(expression, message) {  \
    static_assert(expression, message);        \
    SUCCEED(message);                          \
}

That way it's automatically statically tested, and logged. It would be nice for the expression to be in the output itself; which I guess can be emulated with:

#define STATIC_REQUIRE(expression, message) {  \
    static_assert(expression, message);        \
    REQUIRE(expression);                       \
}

which would actually test twice, once at compile time and once at run time; though it should be inexpensive as its likely to have been calculated at compile-time.

[martinmoene]

Perhaps you want to be able to also let STATIC_REQUIRE behave as the normal REQUIRE so that compilation may continue where it otherwise would be stopped by a static assertion failure.

Using somewhat like this here

[parnmatt]

I wasn't thinking that; however that's a fantastic idea, and simple to implement with a variable as you've shown.

That would be a great addition to this feature request.

[horenmar]

I like the idea, so I am open to getting the PR in. (I am gonna post feedback on that there)