During the RFC, it was discussed that figuring out whether a range is empty was subtle, and thus there should be a clear and obvious way to do it. It can't just be ExactSizeIterator::is_empty (also unstable) because not all ranges are ExactSize -- not even Range<i32> or RangeInclusive<usize>.
NLL: Limit two-phase borrows to autoref-introduced borrows
This imposes a restriction on two-phase borrows so that it only applies to autoref-introduced borrows.
The goal is to ensure that our initial deployment of two-phase borrows is very conservative. We want it to still cover the `v.push(v.len());` example, but we do not want it to cover cases like `let imm = &v; let mu = &mut v; mu.push(imm.len());`
(Why do we want it to be conservative? Because when you are not conservative, then the results you get, at least with the current analysis, are tightly coupled to details of the MIR construction that we would rather remain invisible to the end user.)
Fix#46747
I decided, for this PR, to add a debug-flag `-Z two-phase-beyond-autoref`, to re-enable the more general approach. But my intention here is *not* that we would eventually turn on that debugflag by default; the main reason I added it was that I thought it was useful for writing tests to be able to write source that looks like desugared MIR.
Namely, the mutable borrows also carries a flag indicating whether
they should support two-phase borrows.
This allows us to thread down, from the point of the borrow's
introduction, whether the particular adjustment that created it is one
that yields two-phase mutable borrows.
Added `-Z two-phase-beyond-autoref` to bring back old behavior (mainly
to allow demonstration of desugared examples).
Updated tests to use aforementioned flag when necessary. (But in each
case where I added the flag, I made sure to also include a revision
without the flag so that one can readily see what the actual behavior
we expect is for the initial deployment of NLL.)
`match`ing on an `Option<Ordering>` seems cause some confusion for LLVM; switching to just using comparison operators removes a few jumps from the simple `for` loops I was trying.
Warn about more ignored bounds in type aliases
It seems that all bounds in type aliases are entirely ignored, not just type bounds. This extends the warning appropriately.
I assume this should be made a hard error with the next epoch? I can't see any reason to accept these programs. (And suddenly enforcing these type bounds would be a breaking change.)
rustc: Add `#[rustc_args_required_const]`
This commit adds a new unstable attribute to the compiler which requires that
arguments to a function are always provided as constants. The primary use case
for this is SIMD intrinsics where arguments are defined by vendors to be
constant and in LLVM they indeed must be constant as well.
For now this is mostly just a semantic guarantee in rustc that an argument is a
constant when invoked, phases like trans don't actually take advantage of it
yet. This means that we'll be able to use this in stdsimd but we won't be able
to remove the `constify_*` macros just yet. Hopefully soon though!
Implement RFC 2052 (Epochs)
This adds -Zepochs and uses it for tyvar_behind_raw_pointer (#46906)
When we move this to --epoch=XXX, we'll need to gate the 2018 epoch on nightly, but not the 2015 one. I can make these changes here itself though it's kinda pointless given that the entire flag is nightly-only.
r? @nikomatsakis @aturon
cc #44581 (epoch tracking)
cc #46906 (tyvar_behind_raw_pointer)
Implement TrustedLen for Take<Repeat> and Take<RangeFrom>
This will allow optimization of simple `repeat(x).take(n).collect()` iterators, which are currently not vectorized and have capacity checks.
This will only support a few aggregates on `Repeat` and `RangeFrom`, which might be enough for simple cases, but doesn't optimize more complex ones. Namely, Cycle, StepBy, Filter, FilterMap, Peekable, SkipWhile, Skip, FlatMap, Fuse and Inspect are not marked `TrustedLen` when the inner iterator is infinite.
Previous discussion can be found in #47082
r? @alexcrichton
Export wasm source map when debug information is enabled
We use binaryen's linker to produce a wasm file (via s2wasm). The wasm writer has capabilities to export source maps. The pilot support for source maps is added to Firefox.
The produced source map contains references to the original file, that might require additional source map file processing to include / package original files with it.
/cc @alexcrichton
Add filtering options to `rustc_on_unimplemented`
- Add filtering options to `rustc_on_unimplemented` for local traits, filtering on `Self` and type arguments.
- Add a way to provide custom notes.
- Tweak binops text.
- Add filter to detect wether `Self` is local or belongs to another crate.
- Add filter to `Iterator` diagnostic for `&str`.
Partly addresses #44755 with a different syntax, as a first approach. Fixes#46216, fixes#37522, CC #34297, #46806.
[NLL] Improve DefiningTy::Const
Fixes#47590 by fixing the way DefiningTy represents constants. Previously, constants were represented using just the type of the variable. However, this will fail to capture early-bound regions as NLL inference vars, resulting in an ICE when we try to compute region VIDs a little bit later in the universal
region resolution process. (ref #47590)
Fixes#47590 by fixing the way DefiningTy represents constants. Previously,
constants were represented using just the type of the variable. However, this
will fail to capture early-bound regions as NLL inference vars, resulting in an
ICE when we try to compute region VIDs a little bit later in the universal
region resolution process.
MIR-borrowck: augmented assignment causes duplicate errors
Fixes#45697. This PR resolves the error duplication. I attempted to replace the existing sets since there were quite a few but only managed to replace two of them.
r? @nikomatsakis
Document that associated constants prevent a trait from being made into an object
Fixes https://github.com/rust-lang/rust/issues/47952
Add a short mention of associated constants to E0038
Use time crate in bootstrap dist instead of date
`bootstrap dist` command is trying to run *NIX specific `date` command to get current month and year. This command keep failing when it's called on a Windows command prompt. This patch is making it use time crate.
Closes: #47908
libtest: Replace panics with error messages
This replaces explicit panics on failures in libtest with prints to stderr.
Where "failures" == CLI argument parsing and such
Before:
```
$ ./foo-stable --not-an-option
thread 'main' panicked at '"Unrecognized option: \'not-an-option\'"', libtest/lib.rs:251:27
note: Run with `RUST_BACKTRACE=1` for a backtrace.
```
After:
```
$ ./foo-nightly --not-an-option
error: Unrecognized option: 'not-an-option'
```
Document std::os::raw.
This adds a brief explanation to each type and its definition according to C. This also helps clarify that the definitions of the types, as described by rustdoc, are not necessarily the same from platform to platform.
Warn when rustc output conflicts with existing directories
When the compiled executable would conflict with a directory, display a
rustc error instead of a verbose and potentially-confusing linker
error. This is a usability improvement, and doesn’t actually change
behaviour with regards to compilation success. This addresses the
concern in #35887. Fixes#13098.
Previously, when the type of a method receiver could not be determined,
the error message would, potentially confusingly, highlight the span of
the entire method call.
Resolves#36598, resolves#42234.
This commit adds a new unstable attribute to the compiler which requires that
arguments to a function are always provided as constants. The primary use case
for this is SIMD intrinsics where arguments are defined by vendors to be
constant and in LLVM they indeed must be constant as well.
For now this is mostly just a semantic guarantee in rustc that an argument is a
constant when invoked, phases like trans don't actually take advantage of it
yet. This means that we'll be able to use this in stdsimd but we won't be able
to remove the `constify_*` macros just yet. Hopefully soon though!
