[NLL] make temp for each candidate in `match` arm
In NLL, `ref mut` patterns leverage the two-phase borrow infrastructure to allow the shared borrows within a guard before the "activation" of the mutable borrow when we begin execution of the match arm's body. (There is further discussion of this on PR #50783.)
To accommodate the restrictions we impose on two-phase borrows (namely that there is a one-to-one mapping between each activation and the original initialization), this PR is making separate temps for each candidate pattern. So in an arm like this:
```rust
PatA(_, ref mut ident) |
PatB(ref mut ident) |
PatC(_, _, ref mut ident) |
PatD(ref mut ident) if guard_stuff(ident) => ...
```
instead of 3 temps (two for the guard and one for the arm body), we now have 4 + 2 temps associated with `ident`: one for each candidate plus the actual temp that the guard uses directly, and then the sixth is the temp used in the arm body.
Fix#51348
Add `-Z borrowck=migrate`
This adds `-Z borrowck=migrate`, which represents the way we want to migrate to NLL under Rust versions to come. It also hooks this new mode into `--edition 2018`, which means we're officially turning NLL on in the 2018 edition.
The basic idea of `-Z borrowck=migrate` that there are cases where NLL is fixing old soundness bugs in the borrow-checker, but in order to avoid just breaking code by immediately rejecting the programs that hit those soundness bugs, we instead use the following strategy:
If your code is accepted by NLL, then we accept it.
If your code is rejected by both NLL and the old AST-borrowck, then we reject it.
If your code is rejected by NLL but accepted by the old AST-borrowck, then we emit the new NLL errors as **warnings**.
These warnings will be turned into hard errors in the future, and they say so in these diagnostics.
Fix#46908
Rollup of 16 pull requests
Successful merges:
- #52558 (Add tests for ICEs which no longer repro)
- #52610 (Clarify what a task is)
- #52617 (Don't match on region kinds when reporting NLL errors)
- #52635 (Fix #[linkage] propagation though generic functions)
- #52647 (Suggest to take and ignore args while closure args count mismatching)
- #52649 (Point spans to inner elements of format strings)
- #52654 (Format linker args in a way that works for gcc and ld)
- #52667 (update the stdsimd submodule)
- #52674 (Impl Executor for Box<E: Executor>)
- #52690 (ARM: expose `rclass` and `dsp` target features)
- #52692 (Improve readability in a few sorts)
- #52695 (Hide some lints which are not quite right the way they are reported to the user)
- #52718 (State default capacity for BufReader/BufWriter)
- #52721 (std::ops::Try impl for std::task::Poll)
- #52723 (rustc: Register crates under their real names)
- #52734 (sparc ABI issue - structure returning from function is returned in 64bit registers (with tests))
Failed merges:
- #52678 ([NLL] Use better spans in some errors)
r? @ghost
introduce universes to NLL type check
This branch aims to fix#48071 and also advance chalk integration a bit at the same time. It re-implements the subtyping/type-equating check so that NLL doesn't "piggy back" on the subtyping code of the old type checker.
This new code uses the "universe-based" approach to handling higher-ranked lifetimes, which sidesteps some of the limitations of the current "leak-based" scheme. This avoids the ICE in #48071.
At the same time, I aim for this to potentially be a kind of optimization. This NLL code is (currently) not cached, but it also generates constraints without doing as much instantiation, substitution, and folding. Right now, though, it still piggy backs on the `relate_tys` trait, which is a bit unfortunate -- it means we are doing more hashing and things than we have to. I want to measure the see the perf. Refactoring that trait is something I'd prefer to leave for follow-up work.
r? @pnkfelix -- but I want to measure perf etc first
rustc: Register crates under their real names
Whenever we register a crate into the crate store, make sure to use the real
name mentioned in the metadata instead of the name mentioned in the `extern
crate` statement, as the statement can be wrong!
Closes#51796
std::ops::Try impl for std::task::Poll
I originally left out the `Try` impl for `Poll` because I was curious if we needed it, and @MajorBreakfast and I had discussed the potential for it to introduce confusion about exactly what control-flow was happening at different points. However, after porting a pretty significant chunk of Fuchsia over to futures 0.3, I discovered that I was *constantly* having to do repetitive matching on `Poll<Result<...>>` or `Poll<Option<Result<...>>>` in order to propagate errors correctly. `try_poll` (propagate `Poll::Ready(Err(..))`s) helped in some places, but it was far more common to need some form of conversion between `Result`, `Poll<Result<...>>`, and `Poll<Option<Result<...>>>`. The `Try` trait conveniently provides all of these conversions in addition to a more concise syntax (`?`), so I'd like to experiment with using these instead.
cc @seanmonstar
r? @aturon
Note: this change means that far more futures 0.1 code can work without significant changes since it papers over the fact that `Result` is no longer at the top-level when using `Stream` and `Future` (since it's now `Poll<Result<...>>` or `Poll<Option<Result<...>>>` instead of `Result<Poll<..>>` and `Result<Poll<Option<...>>>`).
ARM: expose `rclass` and `dsp` target features
- `dsp`: the subtarget supports the DSP (saturating arith. and such)
instructions
- `rclass`: target is a Cortex-R
Both features are useful to support ARM MCUs on `coresimd`.
Note: Cortex-R52 is the first Armv8-R with `neon` support.
r? @alexcrichton
cc @japaric
Impl Executor for Box<E: Executor>
removes the need for the compatibility lib between futures 0.1 and 0.3 to use a wrapper type to implement Executor for Box<Executor>
Format linker args in a way that works for gcc and ld
Pass multiple linker arguments rather than concatenate with commas (fixes#52634).
`-l library` -> `-llibrary` to work with apple's ld.
To build with apple's ld I'm currently also passing `-C link-args="-arch x86_64 -macosx_version_min 10.13.0"`. I'll try and understand the latter flag better before PRing that.
This PR currently works for me. Hopefully CI will pick up any grievous ramifications in other toolchains?
Thanks to @alexcrichton for the pointer to the relevant code!
Fix #[linkage] propagation though generic functions
Fixes#18804
In the non-local branch of `get_static` (where the fix was implemented) `span_fatal` had to be replaced with `bug!` as we have no span in that case.
Don't match on region kinds when reporting NLL errors
First half (by number of tests affected) of the changes to "does not live long enough".
Now that lexical MIR borrowck is gone, region kinds are always ReVar, so matching on them to change errors does nothing.
Changes "borrowed value only lives until here" to "`x` is dropped here while still borrowed".
r? @pnkfelix cc @nikomatsakis
Clarify what a task is
Currently we call two distinct concepts "task":
1. The top-level future that is polled until completion
2. The lightweight "thread" that is responsible for polling the top-level future. What additional data beside the future is stored in this type varies between different `Executor` implementations.
I'd prefer to return to the old formulation by @alexcrichton:
```rust
/// A handle to a "task", which represents a single lightweight "thread" of
/// execution driving a future to completion.
pub struct Task {
```
Source: [`task_impl/mod.rs` in futures-rs 0.1](1328fc9e8a/src/task_impl/mod.rs (L49-L50))
I think that this change will make it much easier to explain everything.
r? @aturon
@cramertj
As a driveby change, I made `#![feature(nll)]` *always* take
precedence over `-Z borrowck`. The main effect this had is that it
means tests with `#![feature(nll)]` will ignore uses of `-Z
borrowck=compare`. This affected only one test as far as I can tell,
and I think that test used `-Z borrowck=compare` only as a historical
accident.
Note that this test is carefully crafted to *try* to not segfault
during its run. Howver, it really is representing unsound code that
should be rejected after we manage to remove the AST-borrowck entirely
from the compiler.
Also convert an ICE that became reachable code under borrowck=migrate
into a normally reported error (which is then downgraded to a
warning). This actually has a nice side benefit of providing a
somewhat more useful error message, at least in the particular case of
the example from issue #27282.
