Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

Co-Authored-By: Jonas Schievink <jonasschievink@gmail.com>
Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

…parisons and filter(x).next() calls.

…Simulacrum

Update RELEASES.md for 1.42.0

### [Rendered](https://github.com/XAMPPRocky/rust/blob/relnotes-1.42.0/RELEASES.md)

r? @Mark-Simulacrum
cc @rust-lang/release

…matsakis

instantiate_value_path: on `SelfCtor`, avoid unconstrained tyvars

Fixes rust-lang#69306.

On `Self(...)` (that is, a `Res::SelfCtor`), do not use `self.impl_self_ty(...)`. The problem with that method is that it creates unconstrained inference variables for type parameters in the `impl` (e.g. `impl<T> S0<T>`). These variables then eventually get substituted for something else when they come in contact with the expected type (e.g. `S0<u8>`) or merely the arguments passed to the tuple constructor (e.g. the `0` in `Self(0)`).

Instead of using `self.impl_self_ty(...)`, we instead merely use `let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));` to get the rewritten `res`.

r? @eddyb

parser: `token` -> `normalized_token`, `nonnormalized_token` -> `token`

So, after rust-lang#69006, its follow-ups and an attempt to remove `Parser::prev_span` I came to the conclusion that the unnormalized token and its span is what you want in most cases, so it should be default.

Normalization only makes difference in few cases where we are checking against `token::Ident` or `token::Lifetime` specifically.
This PR uses `normalized_token` for those cases.

Using normalization explicitly means that people writing code should remember about `NtIdent` and `NtLifetime` in general. (That is alleviated by the fact that `token.ident()` and `fn parse_ident_*` are already written.)
Remembering about `NtIdent`, was, however, already the case, kind of, because the implicit normalization was performed only for the current/previous token, but not for things like `look_ahead`.
As a result, most of token classification methods in `token.rs` already take `NtIdent` into account (this PR fixes a few pre-existing minor mistakes though).

The next step is removing `normalized(_prev)_token` entirely and replacing it with `token.ident()` (mostly) and `token.normalize()` (occasionally).
I want to make it a separate PR for that and run it though perf.
`normalized_token` filled on every bump has both a potential to avoid repeated normalization, and to do unnecessary work in advance (it probably doesn't matter anyway, the normalization is very cheap).

r? @Centril

typeck: use `Pattern` obligation cause more for better diagnostics

r? @estebank

…c-morse

use char instead of &str for single char patterns

error_derive_forbidden_on_non_adt: be more graceful

Fixes rust-lang#69341 which was injected by rust-lang#67052.

r? @petrochenkov

…entril

Stabilize `boxed_slice_try_from`

Closes rust-lang#69202

late resolve, visit_fn: bail early if there's no body.

Fixes rust-lang#69401 which was injected by rust-lang@b2c6eeb in rust-lang#68788.

r? @petrochenkov

Remove unneeded calls to format!()

…lacrum

remove redundant clones, references to operands, explicit boolean comparisons and filter(x).next() calls.