Various never type test improvements
I want to make sure that the never type ui tests are actually sensible, and to do so I'm trying to clean them up. This mainly adds comments explaining test purposes and removes outdated stuff.
I imagine best reviewed commit-by-commit, I tried to write useful descriptions and group things into small commits.
cc `@lcnr` (I removed `fallback`/`nofallback` terminology in b5f82d4716d0d978b89034c902f88e2d449da636)
Gate tests with the right edition
This PR guarantees that `./x test --test-args="--edition XXXX" ui` runs correctly with the 2015, 2018 and 2021 editions.
I don't expect this PR to hold up over time but it helps to submit further updates to the `//@ edition` directives of tests where we can use the new range syntax to have a more robust testing across different editions
r? `@fmease`
---
try-job: aarch64-gnu
try-job: aarch64-apple
try-job: x86_64-msvc-1
try-job: i686-msvc-1
try-job: x86_64-mingw-1
try-job: test-various
try-job: armhf-gnu
Turn moves into copies after copy propagation
Previously copy propagation presumed that there is further unspecified distinction between move operands and copy operands in assignments and propagated moves from assignments into terminators. This is inconsistent with current operational semantics.
Turn moves into copies after copy propagation to preserve existing behavior.
Fixes https://github.com/rust-lang/rust/issues/137936.
Fixes https://github.com/rust-lang/rust/issues/146423.
r? `@cjgillot`
Skip unused variables warning for unreachable code
Fixesrust-lang/rust#148373
These warnings are not reported on stable branch, but are now reported on the beta.
I tried another solution to record whether a `local` is reachable in `find_dead_assignments`, but the code in this PR seems simpler.
r? `@cjgillot`
Fix the issue of unused assignment from MIR liveness checking
Fixesrust-lang/rust#148960Fixesrust-lang/rust#148418
r? ``@davidtwco``
cc ``@cjgillot``
My first try on MIR related code, so it may not be the best fix.
Previously copy propagation presumed that there is further unspecified
distinction between move operands and copy operands in assignments and
propagated moves from assignments into terminators. This is inconsistent
with current operational semantics.
Turn moves into copies after copy propagation to preserve existing behavior.
Fixes https://github.com/rust-lang/rust/issues/137936.
Fixes https://github.com/rust-lang/rust/issues/146423.
unused_must_use: Don't warn on `Result<(), Uninhabited>` or `ControlFlow<Uninhabited, ()>`
This suppresses warnings on things like `Result<(), !>`, which helps simplify code using the common pattern of having an `Error` associated type: code will only have to check the error if there is a possibility of error.
This will, for instance, help with future refactorings of `write!` in the standard library.
As this is a user-visible change to lint behavior, it'll require a lang FCP.
---
My proposal, here, is that we handle this simple case to make common patterns more usable. This does not rule out the possibility of adding more cases in the future, including general trait-based cases. However, I don't think we should make this common case wait on the more general cases. In particular, this solution does not close any doors on replacing this special case with a general case.
This would unblock some planned work in the standard library to make `write!` more usable for infallible cases (e.g. writing into a `Vec` or `String`).
This suppresses warnings on things like `Result<(), !>`, which helps
simplify code using the common pattern of having an `Error` associated
type: code will only have to check the error if there is a possibility
of error.
