Add more links in panic docs
Fixes#48695 by adding a link to `AssertUnwindSafe`. Also added some other links in the module's docs to make things clearer.
Make `Vec::new` a `const fn`
`RawVec::empty/_in` are a hack. They're there because `if size_of::<T> == 0 { !0 } else { 0 }` is not allowed in `const` yet. However, because `RawVec` is unstable, the `empty/empty_in` constructors can be removed when #49146 is done...
Bury Error::description()
Second attempt of #49536https://github.com/rust-lang/rfcs/pull/2230
The exact wording of the default implementation is still up in the air, but I think it's a detail that can be amended later.
A previous PR fixed one method that was legitimately buggy;
this cleans up the rest to be less diverse, mirroring the
corresponding impls on [T] to the greatest extent possible
without introducing any unnecessary UTF-8 boundary checks at 0.
On NetBSD the initial mmap() protection of a mapping can not be made
less restrictive with mprotect().
So when mapping a stack guard page, use the maximum protection
we ever want to use, then mprotect() it to the permission we
want it to have initially.
Warn on pointless #[derive] in more places
This fixes the regression in #49934 and ensures that unused `#[derive]` invocations on statements, expressions and generic type parameters survive to trip the `unused_attributes` lint. There is a separate warning hardcoded for `#[derive]` on macro invocations since linting (even the early-lint pass) occurs after expansion. This also adds regression tests for some nodes that were already warning properly.
closes#49934
This fixes the regression in #49934 and ensures that unused `#[derive]`s on statements, expressions and generic type parameters survive to trip the `unused_attributes` lint. For `#[derive]` on macro invocations it has a hardcoded warning since linting occurs after expansion. This also adds regression testing for some nodes that were already warning properly.
closes#49934
