Stabilize ptr::slice_from_raw_parts[_mut]
Closes#36925, the tracking issue.
Initial impl: #60667
r? @rust-lang/libs
In addition to stabilizing, I've adjusted the example of `ptr::slice_from_raw_parts` to use `slice_from_raw_parts` instead of `slice_from_raw_parts_mut`, which was unnecessary for the example as written.
check_match: extract common logic
This is part of work on `hir::ExprKind::Let` which I thought made sense on its own (though makes even more sense with `::Let`).
r? @oli-obk
Bump LLVM submodule to fix LLVM assertion failure in MSP430 interrupt generation.
This PR brings in changes introduced by [this cherry-pick](https://github.com/rust-lang/llvm-project/pull/37) to the Rust repository.
Nightlies downloaded from `rustup` do not appear to have llvm assertions enabled; the assertion failure [sometimes](https://github.com/YuhanLiin/msp430fr2355-quickstart/issues/3) causes link errors that shouldn't occur. I couldn't find any indication of other bugs; however, it should still be fixed.
Stabilize the debug_map_key_value feature
RFC: https://github.com/rust-lang/rfcs/pull/2696
Tracking issue: #62482
Stabilizes the `debug_map_key_value` feature, which covers:
```rust
impl<'a, 'b> DebugMap<'a, 'b> {
pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {}
pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {}
}
```
These methods are small and self-contained, and are used as the basis for the existing `DebugMap::entry` method, so have been used in the wild for the last 6 months or so.
Update cargo
2 commits in b68b0978ab8012f871c80736fb910d14b89c4498..9d32b7b01409024b165545c568b1525d86e2b7cb
2020-01-24 18:26:23 +0000 to 2020-01-26 18:27:29 +0000
- Polish code to clarify meaning (rust-lang/cargo#7836)
- Store maximum queue length (rust-lang/cargo#7829)
don't clone types that are copy, round two.
Apparently fixing some of these issues makes clippy find even more so I did a couple of rounds now.
r? @eddyb
Add leading_ones and trailing_ones methods to the primitive integer types
I was surprised these were missing (given that `leading_zeros` and `trailing_zeros` exist), and they seem trivial and hopefully not controversial.
Note that there's some precedent in that `count_ones` and `count_zeros` are both supported even though only one of these has an intrinsic.
I'm not sure if these need a `rustc_const_unstable` flag (the tests don't seem to mind that it's missing). I just made them const, since there's not really any reason for these to be non-const when the `_zeros` variants are const.
Note: My understanding is trivial stuff like (hopefully) this can land without an RFC, but I'm not fully sure about the process though. Questions like "when does the tracking issue get filed?", are a total mystery to me. So, any guidance is appreciated, and sorry in advance if I should have gone through some more involved process for this.
Suggest defining type parameter when appropriate
```
error[E0412]: cannot find type `T` in this scope
--> file.rs:3:12
|
3 | impl Trait<T> for Struct {}
| - ^ not found in this scope
| |
| help: you might be missing a type parameter: `<T>`
```
Fix#64298.
Stabilize `#[repr(transparent)]` on `enum`s in Rust 1.42.0
# Stabilization report
The following is the stabilization report for `#![feature(transparent_enums)]`.
Tracking issue: https://github.com/rust-lang/rust/issues/60405
[Version target](https://forge.rust-lang.org/#current-release-versions): 1.42 (2020-01-30 => beta, 2020-03-12 => stable).
## User guide
A `struct` with only a single non-ZST field (let's call it `foo`) can be marked as `#[repr(transparent)]`. Such a `struct` has the same layout and ABI as `foo`. Here, we also extend this ability to `enum`s with only one variant, subject to the same restrictions as for the equivalent `struct`. That is, you can now write:
```rust
#[repr(transparent)]
enum Foo { Bar(u8) }
```
which, in terms of layout and ABI, is equivalent to:
```rust
#[repr(transparent)]
struct Foo(u8);
```
## Motivation
This is not a major feature that will unlock new and important use-cases. The utility of `repr(transparent)` `enum`s is indeed limited. However, there is still some value in it:
1. It provides conceptual simplification of the language in terms of treating univariant `enum`s and `struct`s the same, as both are product types. Indeed, languages like Haskell only have `data` as the only way to construct user-defined ADTs in the language.
2. In rare occasions, it might be that the user started out with a univariant `enum` for whatever reason (e.g. they thought they might extend it later). Now they want to make this `enum` `transparent` without breaking users by turning it into a `struct`. By lifting the restriction here, now they can.
## Technical specification
The reference specifies [`repr(transparent)` on a `struct`](https://doc.rust-lang.org/nightly/reference/type-layout.html#the-transparent-representation) as:
> ### The transparent Representation
>
> The `transparent` representation can only be used on `struct`s that have:
> - a single field with non-zero size, and
> - any number of fields with size 0 and alignment 1 (e.g. `PhantomData<T>`).
>
> Structs with this representation have the same layout and ABI as the single non-zero sized field.
>
> This is different than the `C` representation because a struct with the `C` representation will always have the ABI of a `C` `struct` while, for example, a struct with the `transparent` representation with a primitive field will have the ABI of the primitive field.
>
> Because this representation delegates type layout to another type, it cannot be used with any other representation.
Here, we amend this to include univariant `enum`s as well with the same static restrictions and the same effects on dynamic semantics.
## Tests
All the relevant tests are adjusted in the PR diff but are recounted here:
- `src/test/ui/repr/repr-transparent.rs` checks that `repr(transparent)` on an `enum` must be univariant, rather than having zero or more than one variant. Restrictions on the fields inside the only variants, like for those on `struct`s, are also checked here.
- A number of codegen tests are provided as well:
- `src/test/codegen/repr-transparent.rs` (the canonical test)
- `src/test/codegen/repr-transparent-aggregates-1.rs`
- `src/test/codegen/repr-transparent-aggregates-2.rs`
- `src/test/codegen/repr-transparent-aggregates-3.rs`
- `src/test/ui/lint/lint-ctypes-enum.rs` tests the interactions with the `improper_ctypes` lint.
## History
- 2019-04-30, RFC https://github.com/rust-lang/rfcs/pull/2645
Author: @mjbshaw
Reviewers: The Language Team
This is the RFC that proposes allowing `#[repr(transparent)]` on `enum`s and `union`.
- 2019-06-11, PR https://github.com/rust-lang/rust/pull/60463
Author: @mjbshaw
Reviewers: @varkor and @rkruppe
The PR implements the RFC aforementioned in full.
- 2019, PR https://github.com/rust-lang/rust/pull/67323
Author: @Centril
Reviewers: @davidtwco
The PR reorganizes the static checks taking advantage of the fact that `struct`s and `union`s are internally represented as ADTs with a single variant.
- This PR stabilizes `transparent_enums`.
## Related / possible future work
The remaining work here is to figure out the semantics of `#[repr(transparent)]` on `union`s and stabilize those. This work continues to be tracked in https://github.com/rust-lang/rust/issues/60405.
rustc_span: return an impl Iterator instead of a Vec from macro_backtrace.
Having `Span::macro_backtrace` produce an `impl Iterator<Item = ExpnData>` allows #67359 to use it instead of rolling its own similar functionality.
The move from `MacroBacktrace` to `ExpnData` (which the first two commits are prerequisites for) both eliminates unnecessary allocations, and is strictly more flexible (exposes more information).
r? @petrochenkov
```
error[E0412]: cannot find type `T` in this scope
--> file.rs:3:12
|
3 | impl Trait<T> for Struct {}
| - ^ not found in this scope
| |
| help: you might be missing a type parameter: `<T>`
```
Fix#64298.
perf: Avoid creating a SmallVec if nothing changes during a fold
Not sure if this helps but in theory it should be less work than what
the current micro optimization does for `ty::Predicate` lists.
(It would explain the overhead I am seeing from `perf`.)
bors