People often come looking for some kind of `as_ref_unchecked` method on
raw pointers that would give them `&T` and not `Option<&T>` when they
are sure the pointer is not NULL.
There's no such method, but taking a reference of the dereferenced
pointer accomplishes the same thing. Therefore, suggest using that, at
the `as_ref` site ‒ it's a place people are likely going to look into.
debug_assert to ensure that from_raw_parts is only used properly aligned
This does not help nearly as much as I would hope because everybody uses the distributed libstd which is compiled without debug assertions. For this reason, I am not sure if this is even worth it. OTOH, this would have caught the misalignment fixed by https://github.com/rust-lang/rust/issues/42789 *if* there had been any tests actually using ZSTs with alignment >1 (we have a CI runner which has debug assertions in libstd enabled), and it seems to currently [fail in the rg testsuite](https://ci.appveyor.com/project/rust-lang/rust/build/1.0.8403/job/v7dfdcgn8ay5j6sb). So maybe it is worth it, after all.
I have seen the attribute `#[rustc_inherit_overflow_checks]` in some places, does that make it so that the *caller's* debug status is relevant? Is there a similar attribute for `debug_assert!`? That could even subsume `rustc_inherit_overflow_checks`: Something like `rustc_inherit_debug_flag` could affect *all* places that change the generated code depending on whether we are in debug or release mode. In fact, given that we have to keep around the MIR for generic functions anyway, is there ever a reason *not* to handle the debug flag that way? I guess currently we apply debug flags like `cfg` so this is dropped early during the MIR pipeline?
EDIT: I learned from @eddyb that because of how `debug_assert!` works, this is not realistic. Well, we could still have it for the rustc CI runs and then maybe, eventually, when libstd gets compiled client-side and there is both a debug and a release build... then this will also benefit users.^^
Use #[non_exhaustive] on internal enums
This replaces `__Nonexhaustive` variants (and variants thereof) with `#[non_exhaustive]`. These were mostly unstable previously, with the exception of the `cloudabi` enums and `Level` in proc_macro: these were `#[doc(hidden)]`, so clearly intended not to be used directly. It should be safe to replace all of these.
Don't accept non-string literals for the format string in writeln
This is to improve diagnostics.
`println` and `eprintln` were already fixed by #52394.
Fixes#30143
unsized ManuallyDrop
I think this matches what @eddyb had in https://github.com/rust-lang/rust/pull/52711 originally.
~~However, I have never added a `CoerceUnsized` before so I am not sure if I did this right. I copied the `unstable` attribute on the `impl` from elsewhere, but AFAIK it is useless because `impl`'s are insta-stable... so shouldn't this rather say "stable since 1.30"?~~
This is insta-stable and hence requires FCP, at least.
Fixes https://github.com/rust-lang/rust/issues/47034
Add links to std::char::REPLACEMENT_CHARACTER from docs.
There are a few places where we mention the replacement character in the
docs, and it could be helpful for users to utilize the constant which is
available in the standard library, so let’s link to it!
There are a few places where we mention the replacement character in the
docs, and it could be helpful for users to utilize the constant which is
available in the standard library, so let’s link to it!
Place unions, pointer casts and pointer derefs behind extra feature gates
To ensure we don't stabilize these things together with const fn stabilization (or any other stabilization)
This PR moves union field accesses inside `const fn` behind a feature gate. It was possible without a feature gate before, but since `const fn` was behind a feature gate we can do this change.
While "dereferencing raw pointers" and "casting raw pointers to usize" were hard errors before this PR, one could work around them by abusing unions:
```rust
// deref
union Foo<T> {
x: &'static T,
y: *const T,
}
const FOO: u32 = unsafe { *Foo { y: 42 as *const T }.x };
// as usize cast
union Bar<T> {
x: usize,
y: *const T,
}
const BAR: usize = unsafe { Bar { y: &1u8 }.x };
```
r? @eddyb
cc @nikomatsakis
Rename Executor trait to Spawn
Renames the `Executor` trait to `Spawn` and the method on `Context` to `spawner`.
Note: Best only merge this after we've the alpha 3 announcement post ready.
r? @cramertj
