Remove unnecessary layout assertions for object-safe receivers
The soundness of `DispatchFromDyn` relies on the fact that, like all other built-in marker-like layout traits (e.g. `Sized`, `CoerceUnsized`), the guarantees that they enforce in *generic* code via traits will result in assumptions that we can rely on in codegen.
Specifically, `DispatchFromDyn` ensures that we end up with a receiver that is a valid pointer type, and its implementation validity recursively ensures that the ABI of that pointer type upholds the `Scalar` or `ScalarPair` representation for sized and unsized pointees, respectively.
The check that this layout guarantee holds for arbitrary, possibly generic receiver types that also may exist in possibly impossible-to-instantiate where clauses is overkill IMO, and leads to several ICEs due to the fact that computing layouts before monomorphization is going to be fallible at best.
This PR removes the check altogether, since it just exists as a sanity check from very long ago, 6f2a161b1b.
Fixes#125810Fixes#90110
This PR is an alternative to #136195. cc `@adetaylor.` I didn't realize in that PR that the layout checks that were being modified were simply *sanity checks*, rather than being actually necessary for soundness.
This is serves as a collection of crashes so that accidental ICE fixes are tracked.
This was formally done at https://github.com/rust-lang/glacier but doing it inside
the rustc testsuite is more convenient.
It is imperative that a test in the suite causes an internal compiler error/panic
or makes rustc crash in some other way.
A test will "pass" if rustc exits with something other than 1 or 0.
When adding crashes from https://github.com/rust-lang/rust/issues, the
issue number should be noted in the file name (12345.rs should suffice)
and also inside the file via //@ known-bug #4321 if possible.
If you happen to fix one of the crashes, please move it to a fitting
subdirectory in tests/ui and give it a meaningful name.
Also please add a doc comment at the top of the file explaining why
this test exists. :)
Adding
Fixes #NNNNN
Fixes #MMMMM
to the description of your pull request will ensure the
corresponding tickets will be closed automatically upon merge.
The ticket ids can be found in the file name or the known-bug annotation
inside the testfile.
Please do not re-report any crashes that you find here!
Matthias Krüger
5da750001d