Avoid collecting an interator just to re-iterate immediately.
Rather reuse the previous iterator. (clippy::needless_collect)

Following up on rust-lang#87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.

It used to allow you to mutate the key, even though that can invalidate the map by creating duplicate keys.

…ry's result

Since this is an example, this could really do with some review from
someone familiar with unsafe stuff !

I made the example no longer `no_run` since it works for me.

Fixes rust-lang#81847

Signed-off-by: Ian Jackson <[email protected]>
Co-authored-by: Amanieu d'Antras <[email protected]>

I attempted that with the previous code, but I misunderstdood how
`shallow_resolve` works.

During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.

This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.

As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).

As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).

Use `/etc/os-release` instead of `/etc/NIXOS`.
The latter one does not exist on NixOS when using tmpfs as root.

…nieu

docs: GlobalAlloc: completely replace example with one that works

Since this is an example, this could really do with some review from someone familiar with unsafe stuff!

I made the example no longer `no_run` since it works for me.

Fixes rust-lang#81847

dont provide fwd declared params to cg defaults

Fixes rust-lang#83938

```rust
#![feature(const_evaluatable_checked, const_generics, const_generics_defaults)]
#![allow(incomplete_features)]

pub struct Bar<const N: usize, const M: usize = { N + 1 }>;
pub fn foo<const N1: usize>() -> Bar<N1> { loop {} }

fn main() {}
```
This PR makes this code no longer ICE, it was ICE'ing previously because when building substs for `Bar<N1>` we would subst the anon ct: `ConstKind::Unevaluated({N + 1}, substs: [N, M])` with substs of `[N1]`. the anon const has forward declared params supplied though so we end up trying to substitute the provided `M` param which causes the ICE.

This PR doesn't handle the predicates of the const so
```rust
trait Foo<const N: usize> { const Assoc: usize; }
pub struct Bar<const N: usize = { <()>::Assoc }> where (): Foo<N>;
```
Resolves to `<() as Foo<N>>::Assoc` which can allow for using fwd declared params indirectly.

```rust
trait Foo<const N: usize> {}
struct Bar<const N: usize = { 2 + 3 }> where (): Foo<N>;
```
This code also ICEs under this PR because instantiating the default's predicates causes an ICE as predicates_of contains predicates with fwd declared params

PR was briefly discussed [in this zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/evil.20preds.20in.20param.20env.20.2386580)

Fix NixOS detection

Use `/etc/os-release` instead of `/etc/NIXOS` for detection.
The latter one does not exist on NixOS when using tmpfs as root.

…dtwco

avoid temporary vectors/reuse iterators

Avoid collecting an interator just to re-iterate immediately.
Rather reuse the previous iterator. (clippy::needless_collect)

Support HIR wf checking for function signatures

During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.

This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.

As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).

As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).

…r=notriddle

Don't display <table> in item summary

Fixes rust-lang#87231.

r? `@notriddle`

…=oli-obk

Recognize bounds on impls as const bounds

r? `@oli-obk`

…=lnicola

⬆️ rust-analyzer

…alfJung

Add comments explaining the unix command-line argument support.

Following up on rust-lang#87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.

r? `@RalfJung`

…pes, r=spastorino

 Make mir borrowck's use of opaque types independent of the typeck query's result

fixes rust-lang#87218
fixes rust-lang#86465

we used to use the typeck results only to generate an obligation for the mir borrowck type to be equal to the typeck result.

When i removed the `fixup_opaque_types` function in rust-lang#87200, I exposed a bug that showed that mir borrowck can't doesn't get enough information from typeck in order to build the correct lifetime mapping from opaque type usage to the actual concrete type. We therefor now fully compute the information within mir borrowck (we already did that, but we only used it to verify the typeck result) and stop using the typeck information.

We will likely be able to remove most opaque type information from the borrowck results in the future and just have all current callers use the mir borrowck result instead.

r? `@spastorino`

…n514

Fix typo in compile.rs