prep work for using timely dataflow with NLL
Two major changes:
**Two-phase borrows are overhauled.** We no longer have two bits per borrow. Instead, we track -- for each borrow -- an (optional) "activation point". Then, for each point P where the borrow is in scope, we check where P falls relative to the activation point. If P is between the reservation point and the activation point, then this is the "reservation" phase of the borrow, else the borrow is considered active. This is simpler and means that the dataflow doesn't have to care about 2-phase at all, at last not yet.
**We no longer support using the MIR borrow checker without NLL.** It is going to be increasingly untenable to support lexical mode as we go forward, I think, and also of increasingly little value. This also exposed a few bugs in NLL mode due to increased testing.
r? @pnkfelix
cc @bobtwinkles
Update `?` repetition disambiguation.
**Do not merge** (yet)
This is a test implementation of some ideas from discussion in https://github.com/rust-lang/rust/issues/48075 . This PR
- disallows `?` repetition from taking a separator, since the separator is never used.
- disallows the use of `?` as a separator. This allows patterns like `$(a)?+` to match `+` and `a+` rather than `a?a?a`. This is a _breaking change_, but maybe that's ok? Perhaps a crater run is the right approach?
cc @durka @alexreg @nikomatsakis
Merge the std_unicode crate into the core crate
[The standard library facade](https://github.com/rust-lang/rust/issues/27783) has historically contained a number of crates with different roles, but that number has decreased over time. `rand` and `libc` have moved to crates.io, and [`collections` was merged into `alloc`](https://github.com/rust-lang/rust/pull/42648). Today we have `core` that applies everywhere, `std` that expects a full operating system, and `alloc` in-between that only requires a memory allocator (which can be provided by users)… and `std_unicode`, which doesn’t really have a reason to be separate anymore. It contains functionality based on Unicode data tables that can be large, but as long as relevant functions are not called the tables should be removed from binaries by linkers.
This deprecates the unstable `std_unicode` crate and moves all of its contents into `core`, replacing them with `pub use` reexports. The crate can be removed later. This also removes the `CharExt` trait (replaced with inherent methods in libcore) and `UnicodeStr` trait (merged into `StrExt`). There traits were both unstable and not intended to be used or named directly.
A number of new items are newly-available in libcore and instantly stable there, but only if they were already stable in libstd.
Fixes#49319.
Replace `structurally_resolved_type` in casts check.
The behaviour of `resolve_type_vars_if_possible` is simpler and infallible. Other minor refactorings.
I'm not sure if this is backwards compatible, in theory resolving obligations between two cast checks could solve a dependency between them, but I don't know if that's actually possible and it doesn't sound like something we'd want to support.
In issue #49588, Michael Lamparski pointed out a scenario in which the
non-shorthand-field-patterns lint could be triggered by a macro-expanded
pattern, in a way which was direly unwieldy for the macro author to guard
against and unreasonable to expect the macro user to take into account. We can
avoid this by not linting patterns that come from macro-expansions. Although
this entails accepting "false negatives" where the lint could genuinely improve
macro-templated code, avoiding the reported "true-but-super-annoying positive"
may be worth the trade? (Some precedent for these relative priorities exists as
no. 47775 (5985b0b0).)
Resolves#49588.
Fix regression in defaults #49344Fixes#49344 by not checking the well-formedness wrt defaults of predicates that contain lifetimes, which is consistent with not checking generic predicates.
r? @nikomatsakis
Expand macros in `extern {}` blocks
This permits macro and proc-macro and attribute invocations (the latter only with the `proc_macro` feature of course) in `extern {}` blocks, gated behind a new `macros_in_extern` feature.
A tracking issue is now open at #49476closes#48747
Remove adjacent all-const match arm hack.
An old fix for moves-in-guards had a hack for adjacent all-const match arms.
The hack was explained in a comment, which you can see here:
https://github.com/rust-lang/rust/pull/22580/files#diff-402a0fa4b3c6755c5650027c6d4cf1efR497
But hack was incomplete (and thus unsound), as pointed out here:
https://github.com/rust-lang/rust/issues/47295#issuecomment-357108458
Plus, it is likely to be at least tricky to reimplement this hack in
the new NLL borrowck.
So rather than try to preserve the hack, we want to try to just remove
it outright. (At least to see the results of a crater run.)
[breaking-change]
This is a breaking-change, but our hope is that no one is actually
relying on such an extreme special case. (We hypothesize the hack was
originally added to accommodate a file in our own test suite, not code
in the wild.)
Easy edition feature flag
We no longer gate features on epochs; instead we have a `#![feature(rust_2018_preview)]` that flips on a bunch of features (currently dyn_trait).
Based on #49001 to avoid merge conflicts
r? @nikomatsakis
Enable target_feature on any LLVM 6+
In `LLVMRustHasFeature()`, rather than using `MCInfo->getFeatureTable()`
that is specific to Rust's LLVM fork, we can use this in LLVM 6:
/// Check whether the subtarget features are enabled/disabled as per
/// the provided string, ignoring all other features.
bool checkFeatures(StringRef FS) const;
Now rustc using external LLVM can also have `target_feature`.
r? @alexcrichton
An old fix for moves-in-guards had a hack for adjacent all-const match arms.
The hack was explained in a comment, which you can see here:
https://github.com/rust-lang/rust/pull/22580/files#diff-402a0fa4b3c6755c5650027c6d4cf1efR497
But hack was incomplete (and thus unsound), as pointed out here:
https://github.com/rust-lang/rust/issues/47295#issuecomment-357108458
Plus, it is likely to be at least tricky to reimplement this hack in
the new NLL borrowck.
So rather than try to preserve the hack, we want to try to just remove
it outright. (At least to see the results of a crater run.)
[breaking-change]
This is a breaking-change, but our hope is that no one is actually
relying on such an extreme special case. (We hypothesize the hack was
originally added to accommodate a file in our own test suite, not code
in the wild.)
In `LLVMRustHasFeature()`, rather than using `MCInfo->getFeatureTable()`
that is specific to Rust's LLVM fork, we can use this in LLVM 6:
/// Check whether the subtarget features are enabled/disabled as per
/// the provided string, ignoring all other features.
bool checkFeatures(StringRef FS) const;
Now rustc using external LLVM can also have `target_feature`.
