In Python, you only need to indent the `def test_foo` by an additional whitespace, to make it a locally scoped function instead of a proper test function.
No, not if you have any sane linter or formatter involved. They wouldn't let you get away with indenting by a single space, but only by multiples of whatever you normally use in the rest of your program.
I mean, some CI system should be checking that "if_code_compiles()" blocks compile somewhere. It should be an error until the CI system has that header and can test both variants.
People are really quick to add optionality like this without understanding the maintenance cost. (Every boolean feature flag increases the number of variants you need to test by 2!) Either make a decision, or check that both sides work. Don't let people check in dead code.
