…ntCtxt::new_in_snapshot

new error message: `enum` and `struct` are mutually exclusive
new suggestion: replace `enum struct` with `enum`

- Added `Impl`, `Closure`, ForeignMod` targets
- `Target::name` changed for `Target::Impl`
- Error output for `Target::ForeignMod` changed to "foreign module"

This adds support for rust-lld for Apple *OS targets.

This was tested against targets "aarch64-apple-ios" and "aarch64-apple-ios-sim".

For targets "armv7-apple-ios" and "armv7s-apple-ios", it doesn't link because of
"symbols.o" not being generated with the correct CPU subtype (changes in
the "object" crate needs to be done to support it).

…chenkov

Add support for link-flavor rust-lld for iOS, tvOS and watchOS

This adds support for rust-lld for Apple *OS targets.

This was tested against targets ``aarch64-apple-ios`` and ``aarch64-apple-ios-sim`` with [a simple test program](https://github.com/Thog/rust-lld-apple-target_test).

It currently doesn't work with targets ``armv7-apple-ios`` and ``armv7s-apple-ios`` because of ``symbols.o`` not being generated with the correct CPU subtype. This will require changes in the ``object`` crate to expose an API.

As ``ld64.lld`` requires ``-platform_version`` with the minimal version supported and an sdk version, I made ``rustc_target::apple_base`` public to get access to ``*os_deployment_target``  helper functions and also added ``tvos_deployment_target`` as it was missing.

…ikomatsakis

relate `closure_substs.parent_substs()` to parent fn in NLL

Fixes rust-lang#98589

The discrepancy between early- and late-bound lifetimes is because we map early-bound lifetimes into those found in the `closure_substs` while late-bound lifetimes are mapped into liberated free regions:
https://github.com/rust-lang/rust/blob/5f98537eb7b5f42c246a52c550813c3cff336069/compiler/rustc_borrowck/src/universal_regions.rs#L255-L261

r? `@rust-lang/types`

…r=jackh726

Use `TraitEngine` in more places that don't specifically need `FulfillmentContext::new_in_snapshot`

Not sure if this change is worthwhile, but couldn't hurt re: chalkification

r? types

Recover from C++ style `enum struct`

Closes rust-lang#99625

…n-normalize-error, r=spastorino

Delay a bug when failed to normalize trait ref during specialization

The error messages still kinda suck here but they don't ICE anymore...

Fixes rust-lang#45814
Fixes rust-lang#43037

r? types

Prevent ICE for `doc_alias` on match arm, statement, expression

Fixes rust-lang#99777.

This is a pretty minimal fix that should be safe, since rustdoc doesn't generate documentation for match arms, statements, or expressions. I mentioned in the linked issue that the `doc_alias` target checking should probably be improved to avoid future ICEs, but as a new contributor, I'm not confident enough with the HIR types to make a larger change.