docs: minor stylistic changes to str/string docs
std::string::String.repeat(): slightly rephrase to be more in-line with other descriptions.
add ticks around a few keywords in other descriptions.
Lament the invincibility of the Turbofish
Here a test case is added to ensure that any others attempting to drive the Turbofish to extinction have second thoughts. Previously the [entire test suite would succeed](https://github.com/rust-lang/rust/pull/53511) if generic arguments were accepted without disambiguation, making for [confusing and heartbreaking circumstances](https://github.com/rust-lang/rfcs/pull/2527).
Discourage overuse of mem::forget
Some uses of `mem::forget` have been replaced by better methods of `Box`, so I've removed obsoleted use-cases from these docs.
I've removed emphasis on leaking, because it's not obvious `mem::forget` does not guarantee leaking of memory: memory of stack-allocated objects and values partially moved out of `Box` will still be freed. That's a potential error when used to pass objects to FFI, so it's better to direct users to `Box::into_raw` instead.
Use optimized SmallVec implementation
This PR replaces current SmallVec implementation with the one from the Servo project.
Closes https://github.com/rust-lang/rust/issues/51640
r? @Mark-Simulacrum
Feature gate where clauses on associated type impls
Fixes#52913. This doesn't address the core problem, which is tracked by https://github.com/rust-lang/rust/issues/47206. However, it fixes the stable-to-stable regression: you now have to enable `#![feature(generic_associated_types)]` to trigger the weird behaviour.
- Original cycle error diagnostics PR'd against this issue caught
panic-causing error while resolving std::mem::transmute calls
- Now, catch invalid use case of not providing a concrete sized type
behind existential type in definining use case.
- Update relevant test to reflect this new error
52985: revert normalize query changes
- PR 53588 invalidates 53316, causing a correct cycle error to occur
with a good span.
- Don't need to revert the whole merge as the test files are
still fine, just need to revert the normalize query changes.
- It should now be correct that infinite recursion detected during
normalize query type folding is a bug, should have been caught earlier
(when resolving the existential type's defining use cases).
52985: code review impl
- Only cause cycle error if anonymous type resolves to anonymous type
that has the same def id (is the same type) as the original (parent)
type.
- Add test case to cover this case for existential types.
52985: remove Ty prefix from TyAnon
- To align with changes per commit 6f637da50c56a22f745fd056691da8c86824cd9b
