Test conditional initialization validation in async fns
r? @cramertj
Per [paper doc](https://paper.dropbox.com/doc/async.await-Call-for-Tests--AiWF2Nt8tgDiA70qFI~oiLOOAg-nMyZGrra7dz9KcFRMLKJy) calling for async/.await tests, tests are desired for conditionally initialized local variables. This PR hopes to provide tests for that.
#63294 seems to be tracking the items from the paper doc that this PR is related to
#62121 is an open issue asking for more async/.await tests that this relates to
---
👍 executed 2 new tests
👍 tidy
pretty-pretty extremal constants!
(A resurrection of the defunct #57073.)
While many programmers may intuitively appreciate the significance of "magic numbers" like −2147483648, Rust is about empowering everyone to build reliable and efficient software! It's a bit more legible to print the constant names (even noisy fully-qualified-paths thereof).
The bit-manipulation methods mirror those in `librustc_mir::hair::pattern::_match::all_constructors`; thanks to the immortal Varkor for guidance.
Resolves#56393.
r? @varkor
While many programmers may intuitively appreciate the significance of
"magic numbers" like −2147483648, Rust is about empowering everyone to
build reliable and efficient software! It's a bit more legible to
print the constant names (even noisy fully-qualified-paths thereof).
The bit-manipulation methods mirror those in
`librustc_mir::hair::pattern::_match::all_constructors`; thanks to the
immortal Varkor for guidance.
Resolves#56393.
tests for async/await drop order
This is just me helping out with https://github.com/rust-lang/rust/issues/62121 where I can.
I'm also going to use this as a public place to collect my thoughts about what has already been done and what hasn't (adding comments to the dropbox paper doc was quickly getting spammy).
I've tried to keep my commit messages similar to the line items on https://paper.dropbox.com/doc/async.await-Call-for-Tests--AiKouT0L41mSnK1741s~TiiRAg-nMyZGrra7dz9KcFRMLKJy as possible.
A bunch of my tests are likely to be either redundant with other tests, or lower quality than other tests that people are writing. A reasonable approach might be to tell me which commits you want to keep and I'll throw away the rest of them.
The part from the dropbox paper doc that I'm concentrating on here is:
(items marked with `?` are ones that I can't immediately think of how to test, so I will leave for other people. Items with checkboxes are things that I have done or will try to do next)
### Dynamic semantics
- `async`/`await` with unusual locals:
- ? partially uninhabited
- ? conditionally initialized
- ~drop impls~ already done in src/test/ui/async-await/drop-order/*
- ? nested drop impls
- ~partially moved (e.g., `let x = (vec![], vec![]); drop(x.0); foo.await; drop(x.1);`)~ see https://github.com/rust-lang/rust/pull/63310
- Control flow:
- basic
- complex
- [x] `.await` while holding variables of different sizes
- (possibly) drop order
- [x] including drop order for locals when a future is dropped part-way through execution
- Parameters' drop order is covered in my commit f40190a
- ~An async fn version of `dynamic-drop.rs`~
- already done by matthewjasper in https://github.com/rust-lang/rust/pull/62193/files
- ? interaction with const eval, promoteds, and temporaries
- [x] drop the resulting future and check that local variables and parameters are dropped in the expected order (interaction with cancellation, in other words)
- also in f40190a
Explanation of commits:
* 0a1bdd4 is the simplest place I could think of to explicitly test `.await` while holding variables of different sizes. I'm pretty sure that this will end up being redundant with something else, so I'm happy to drop it.
* f40190a is a copy-paste from `drop-order-for-async-fn-parameters.rs` with `NeverReady.await` dumped on the end of each testcase.
* Normally I don't like copy-paste-based tests, but `drop-order-for-async-fn-parameters-by-ref-binding.rs` is also copy-paste, so I thought it might be okay.
* [x] I'm a bit sad that this doesn't cover non-parameter locals, but I think it should be easy enough to extend in that direction, so I might have a crack at that tomorrow.
* c4940e0f90 makes a bunch of local variables and moves them into either `{}` blocks or `async move {}` blocks, checking for any surprising differences.
* I have tried to give the test functions descriptive names
* I have not duplicated the tests for methods with/without self.
* I think that all of these tests could be rewritten to be clearer if I could write down the expected drop order next to each test.
Fix generator size regressions due to optimization
I tested the generator optimizations in #60187 and #61922 on the Fuchsia
build, and noticed that some small generators (about 8% of the async fns
in our build) increased in size slightly.
This is because in #60187 we split the fields into two groups, a
"prefix" non-overlap region and an overlap region, and lay them out
separately. This can introduce unnecessary padding bytes between the two
groups.
In every single case in the Fuchsia build, it was due to there being
only a single variant being used in the overlap region. This means that
we aren't doing any overlapping, period. So it's better to combine the
two regions into one and lay out all the fields at once, which is what
this change does.
r? @cramertj
cc @eddyb @Zoxc
Revert "Rollup merge of #62696 - chocol4te:fix_#62194, r=estebank"
This reverts commit df21a6f040 (#62696), reversing
changes made to cc16d04869.
That PR makes error messages worse than before, and we couldn't come up with a way of actually making them better, so revert it for now. Any idea for making this error message better is welcome!
Fixes#63145.
r? @estebank
Make use of possibly uninitialized data [E0381] a hard error
This is one of the behaviors we no longer allow in NLL. Since it can
lead to undefined behavior, I think it's definitely worth making it a
hard error without waiting to turn off migration mode (#58781).
Closes#60450.
My ulterior motive here is making it impossible to leave variables
partially initialized across a yield (see #60889, discussion at #63035), so
tests are included for that.
cc #54987
---
I'm not sure if bypassing the buffer is a good way of doing this. We could also make a `force_errors_buffer` or similar that gets recombined with all the errors as they are emitted. But this is simpler and seems fine to me.
r? @Centril
cc @cramertj @nikomatsakis @pnkfelix @RalfJung
Remove special code-path for handing unknown tokens
In `StringReader`, we have a buffer of fatal errors, which is used only in a single case: when we see something which is not a reasonable token at all, like `🦀`. I think a more straightforward thing to do here is to produce an explicit error token in this case, and let the next layer (the parser), deal with it.
However currently this leads to duplicated error messages. What should we do with this? Naively, I would think that emitting (just emitting, not raising) `FatalError` should stop other errors, but looks like this is not the case? We can also probably tweak parser on the case-by-case basis, to avoid emitting "expected" errors if the current token is an `Err`. I personally also fine with cascading errors in this case: it's quite unlikely that you actually type a fully invalid token.
@petrochenkov, which approach should we take to fight cascading errors?
This is one of the behaviors we no longer allow in NLL. Since it can
lead to undefined behavior, I think it's definitely worth making it a
hard error without waiting to turn off migration mode (#58781).
Closes#60450.
My ulterior motive here is making it impossible to leave variables
partially initialized across a yield (see discussion at #63035), so
tests are included for that.
Move special treatment of `derive(Copy, PartialEq, Eq)` from expansion infrastructure to elsewhere
As described in https://github.com/rust-lang/rust/pull/62086#issuecomment-515195477.
Reminder:
- `derive(PartialEq, Eq)` makes the type it applied to a "structural match" type, so constants of this type can be used in patterns (and const generics in the future).
- `derive(Copy)` notifies other derives that the type it applied to implements `Copy`, so `derive(Clone)` can generate optimized code and other derives can generate code working with `packed` types and types with `rustc_layout_scalar_valid_range` attributes.
First, the special behavior is now enabled after properly resolving the derives, rather than after textually comparing them with `"Copy"`, `"PartialEq"` and `"Eq"` in `fn add_derived_markers`.
The markers are no longer kept as attributes in AST since derives cannot modify items and previously did it through hacks in the expansion infra.
Instead, the markers are now kept in a "global context" available from all the necessary places, namely - resolver.
For `derive(PartialEq, Eq)` the markers are created by the derive macros themselves and then consumed during HIR lowering to add the `#[structural_match]` attribute in HIR.
This is still a hack, but now it's a hack local to two specific macros rather than affecting the whole expansion infra.
Ideally we should find the way to put `#[structural_match]` on the impls rather than on the original item, and then consume it in `rustc_mir`, then no hacks in expansion and lowering will be required.
(I'll make an issue about this for someone else to solve, after this PR lands.)
The marker for `derive(Copy)` cannot be emitted by the `Copy` macro itself because we need to know it *before* the `Copy` macro is expanded for expanding other macros.
So we have to do it in resolve and block expansion of any derives in a `derive(...)` container until we know for sure whether this container has `Copy` in it or not.
Nasty stuff.
r? @eddyb or @matthewjasper
