This changes removes a cyclic dependency between the "test" and "libtest"
crates, where "libtest" depends on "test" for "black_box", but "test" depends on
"libtest" for everything else.
I've chosen the "hint" module because there seems to be enough consensus in the
discussion of RFC2360 that this module is where such an intrinsic would belong,
but this PR does not implement that RFC! (note: if that RFC ever gets merged,
the API, docs, etc. of this API will need to change).
For backwards compatibility reasons I've chosen to also keep the "test" feature
gate for these instead of adding a new feature gate. If we change the feature
gate, we'll potentially all benchmarks, and while that's something that we could
do, it seems unnecessary to do that now - if RFC2360 gets merged, we'll need to
do that anyways.
libtest: Use deterministic HashMap, avoid spawning thread if there is no concurrency
It seems desirable to make a test and bench runner deterministic, which this achieves by using a deterministic hasher. Also, we we only have 1 thread, we don't bother spawning one and just use the main thread.
The motivation for this is to be able to run the test harness in miri, where we can neither access the OS RNG, nor spawn threads.
Add option to run all tests
This adds the "--include-ignored" flag to libtest, which allows running ignored and unignored tests in one go.
Closes#50363
improve diagnostics for tests with custom return values
This is an attempt at getting the ball rolling to improve the diagnostics for test functions that return custom `impl Termination` values (see #52436).
An alternative could be to use `eprintln!`, but including this in the panic message felt nicely consistent with how failing test assertions would be reported.
Let me know what you think!
Don't format!() string literals
Prefer `to_string()` to `format!()` take 2, this time targetting string literals. In some cases (`&format!("...")` -> `"..."`) also removes allocations. Occurences of `format!("")` are changed to `String::new()`.
