[1.30 beta] tester crate broken

[emilyalbini]

This regression will probably be marked as "won't fix". This issue notifies crate authors.

The tester crate doesn't work anymore on 1.30 beta. The rationale for this is in #53410 (comment).

• tester 0.4.1 regressed from stable to beta (build log) cc @messense

[pnkfelix]

Closing as WONTFIX based on previously linked reasoning #53410 (comment), transcribed below for posterity:

Also @alexcrichton it looks like I broke this: https://crates.io/crates/tester but I don't think that should have ever been allowable in the first place.

It used an implementation detail of how the compiler used libtest to test itself, to trick the stable compiler into thinking that tester was actually libtest and allow it to test itself.