This new documentation tries to avoid to limit the impact of the
conceptual pitfall, that the if guard relaxes the constraint, when
really it tightens it. This is achieved by changing the text and
examples. The previous documentation also chose a rather weird and
non-representative example for the if guard, that made it needlessly
complicated to understand.

- fix small typo
- avoid repetition of formulations

Co-authored-by: Josh Stone <cuviper@gmail.com>

It doesn't need a `Parser` and a `ParseSess`, because the former
contains the latter.

It's always empty.

Most of this method's arguments are usually or always forwarded as-is to
recursive invocations.

Wrapping them in a dedicated struct allows us to document each struct field,
and lets us use struct-update syntax to indicate which arguments are being
modified when making a recursive call.

This test won't work on windows 7, as the Thread::set_name function is
not implemented there (win7 does not provide a documented mechanism to
set thread names).

- Refer to trait directly
- small typo in encapsulate

Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

Existing names for values of this type are `sess`, `parse_sess`,
`parse_session`, and `ps`. `sess` is particularly annoying because
that's also used for `Session` values, which are often co-located, and
it can be difficult to know which type a value named `sess` refers to.
(That annoyance is the main motivation for this change.) `psess` is nice
and short, which is good for a name used this much.

The commit also renames some `parse_sess_created` values as
`psess_created`.

…r=lcnr

constify a couple thread_local statics

Fix LVI tests after frame pointers are enabled by default

rust-lang#121203 enables frame pointers by default. This affects LVI mitigations for the `x86_64-fortanix-unknown-sgx` target. LVI remained mitigated correctly, but the tests were too strict.

``@nshyrei`` , ``@jethrogb``

Add a way to add constructors for `rustc_type_ir` types

Introduces a module called `rustc_type_ir`, in which we can place traits which are named `Ty`/`Region`/`Const`/etc. which expose constructors for the `rustc_type_ir` types. This means we can construct things `Interner::Ty` with `Ty::new_x(...)`, which is needed to uplift the new trait solver into an interner-agnostic crate.

These traits are placed into a *separate* module because they're only intended to be used in interner-agnostic code, and they should mirror the constructors that are provided by the inherent constructor methods in `rustc_middle`.

Putting this up for vibe-check mostly. I haven't copied over any of the type constructors, except for one to create bound types for use in the canonicalizer.

r? lcnr

…documentation, r=cuviper

Improve assert_matches! documentation

This new documentation tries to limit the impact of the conceptual pitfall, that the if guard relaxes the constraint, when really it tightens it. This is achieved by changing the text and examples. The previous documentation also chose a rather weird and non-representative example for the if guard, that made it needlessly complicated to understand.

Extract an arguments struct for `Builder::then_else_break`

Most of this method's arguments are usually or always forwarded as-is to recursive invocations.

Wrapping them in a dedicated struct allows us to document each struct field, and lets us use struct-update syntax to indicate which arguments are being modified when making a recursive call.

---

While trying to understand the lowering of `if` expressions, I found it difficult to keep track of the half-dozen arguments passed through to every call to `then_else_break`. I tried switching over to an arguments struct, and I found that it really helps to make sense of what each argument does, and how each call is modifying the arguments.

I have some further ideas for how to streamline these recursive calls, but I've kept those out of this PR so that it's a pure refactoring with no behavioural changes.

…escr, r=workingjubilee

Small enhancement to description of From trait

- fix small typo
- avoid repetition of formulations

Don't run test_get_os_named_thread on win7

This test won't work on windows 7, as the Thread::set_name function is not implemented there (win7 does not provide a documented mechanism to set thread names).

…wesleywiser

`ParseSess` cleanups

The main change here is to rename all `ParseSess` values as `psess`. Plus a few other small cleanups.

r? `@wesleywiser`

Doc: Fix incorrect reference to integer in Atomic{Ptr,Bool}::as_ptr.

I am assuming "resulting integer" is an error, since we are talking about pointers and booleans here. Seems like it was missed while copy & pasting the docs from the integer versions. I also checked the rest of the docs, and this was the only mention of integers.

…cs, r=ehuss

Update platform-support.md with supported musl version

This just reflects the current status quo, there is no actual change here since the update to musl 1.2.3 occurred in rust-lang#107129 and was approved in rust-lang/compiler-team#572.

I also normalized all mentions of musl libc to "musl" (non-capitalized per the project's site and Wikipedia page).

r? ``@ehuss``