Move trait prototype

[zannabianca1997]

Finishing the work started by @nia-e in #156018 :

Add a barebones implementation for Move (#149607), pending some diagnostics changes & tests.

TODO

• next solver currently errors when not enabling feature(move_trait)
• change printing of trait objects to not show Move
• change printing of opaque types to not show Move
• fix mangling of Move bounds
• how to handle empty trait object that now are dyn Move
• also make sure rustdoc handles move correctly
• valuable to look into why diesel regresses

r? lcnr

[rustbot]

Thanks for the pull request, and welcome! The Rust Project has assigned @lcnr (or someone else) to review your changes, you should hear from them (or someone else) within the next two weeks.

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[zannabianca1997]

A quick ./x.py test tests/ui locally to have a baseline

test result: FAILED. 9 passed; 206 failed; 21862 ignored; 0 measured; 0 filtered out; finished in 1.14s

[zannabianca1997]

test result: FAILED. 21801 passed; 32 failed; 244 ignored; 0 measured; 0 filtered out; finished in 168.70s

wow that were a lot of them. looks like the next batch is a bunch of fn that now has fn() + Move

[zannabianca1997]

looking at the errors, there is also a bunch of (dyn + 'static) printing.

Those are all checks going around the trait_alias feature, that created before empty trait object and now creates what are effectively dyn Move, that are being misprinted.

That sure raises a question - can we handle them now? ummm - putting this aside in favour of lower hanging fruits

[zannabianca1997]

@lcnr this last one (520bc2f)

it's better to break the ABI and accept all aymbol mangling containing Move or we have to decide a way to mangle ?Move? I know rust has no stable abi but to put it in all symbols seems a bit too much

[rust-log-analyzer]

The job x86_64-gnu-gcc-core-tests failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- mem::type_info::test_dynamic_traits stdout ----
---- mem::type_info::test_dynamic_traits stderr ----

thread 'main' (19445) panicked at library/coretests/tests/mem/type_info.rs:364:9:
assertion `left == right` failed: unexpected ids.
actual: [TypeId(0x2cf0839efbfd8a13209e2a8c1b19b866), TypeId(0x91adbabb946c4ff85826d928698757cc)]
expected: [TypeId(0x42aa4cf75b77ce4ad0f41baddeaeca8b)]
  left: {TypeId(0x91adbabb946c4ff85826d928698757cc), TypeId(0x2cf0839efbfd8a13209e2a8c1b19b866)}
 right: {TypeId(0x42aa4cf75b77ce4ad0f41baddeaeca8b)}
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
---- mem::type_info::test_dynamic_traits stdout end ----

failures:
    mem::type_info::test_dynamic_traits

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