See the inline comments for the description of the new algorithm.

Specifically remove V, which can always be VariantIdx, and F, which can
always be Layout.

--wip-- [skip ci]

get the generic text and put it int he suggestion, but suggestion not working on derive subdiagnostic

refactor away from derives and use span_suggestion() instead. Show's the correct(?) generic contents, but overwrites the fn name :(

x fmt

drop commented code and s/todo/fixme

get the correct diagnostic for functions, at least

x fmt

remove some debugs

remove format

remove debugs

remove useless change

remove useless change

remove legacy approach

correct lookahead + error message contains the ident name

fmt

refactor code

tests

add tests

remoev debug

remove comment

Co-authored-by: Takayuki Maeda <[email protected]>

…66_fix, r=TaKO8Ki

 Suggest fix for misplaced generic params on fn item rust-lang#103366

fixes rust-lang#103366

This still has some work to go, but works for 2/3 of the initial base cases described in #1033366

simple fn:
```
error: expected identifier, found `<`
 --> shreys/test_1.rs:1:3
  |
1 | fn<T> id(x: T) -> T { x }
  |   ^ expected identifier
  |
help: help: place the generic parameter list after the function name:
  |
1 | fn id<T>(x: T) -> T { x }
  |    ~~~~

```

Complicated bounds
```
error: expected identifier, found `<`
 --> spanishpear/test_2.rs:1:3
  |
1 | fn<'a, B: 'a + std::ops::Add<Output = u32>> f(_x: B) { }
  |   ^ expected identifier
  |
help: help: place the generic parameter list after the function name:
  |
1 | fn f<'a, B: 'a + std::ops::Add<Output = u32>>(_x: B) { }
  |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Opening a draft PR for comments on approach, particularly I have the following questions:
 -  [x]  Is it okay to be using `err.span_suggestion` over struct derives? I struggled to get the initial implementation (particularly the correct suggestion message) on struct derives, although I think given what I've learned since starting, I could attempt re-doing it with that approach.
  -  [x] in the case where the snippet cannot be obtained from a span, is the `help` but no suggestion okay? I think yes (also, when does this case occur?)
  -  [x] are there any red flags for the generalisation of this work for relevant item kinds (i.e. `struct`, `enum`, `trait`, and `union`). My basic testing indicates it does work for those types except the help tip is currently hardcoded to `after the function name` - which should change dependent on the item.
  - [x] I am planning to not show the suggestion if there is already a `<` after the item identifier, (i.e. if there are already generics, as after a function name per the original issue). Any major objections?
  - [x] Is the style of error okay? I wasn't sure if there was a way to make it display nicer, or if thats handled by span_suggestion

These aren't blocking questions, and I will keep working on:
  - check if there is a `<` after the ident (and if so, not showing the suggestion)
  - generalize the help message
  - figuring out how to write/run/etc ui tests (including reading the docs for them)
  - logic cleanups

rework min_choice algorithm of member constraints

See [this comment](rust-lang#105300 (comment)) for the description of the new algorithm.

Fixes rust-lang#63033
Fixes rust-lang#104639

This uses a more general algorithm than rust-lang#89056 that doesn't treat `'static` as a special case. It thus accepts more code. For example:
```rust
async fn test2<'s>(_: &'s u8, _: &'_ &'s u8, _: &'_ &'s u8) {}
```
I claim it's more correct as well because it fixes rust-lang#104639.

cc `@nikomatsakis` `@lqd` `@tmandry` `@eholk` `@chenyukang` `@oli-obk`

r? types

Use id-based thread parking on SOLID

By using the [`slp_tsk`/`wup_tsk`](https://cs.uwaterloo.ca/~brecht/courses/702/Possible-Readings/embedded/uITRON-4.0-specification.pdf) system functions instead of an event-flag structure, `Parker` becomes cheaper to construct and SOLID can share the implementation used by NetBSD and SGX.

ping `@kawadakk`
r? `@m-ou-se`
`@rustbot` label +T-libs

Remove some superfluous type parameters from layout.rs.

Specifically remove V, which can always be VariantIdx, and F, which can always be Layout.

…oli-obk

Handle discriminant in DataflowConstProp

cc `@jachris`
r? `@JakobDegen`

This PR attempts to extend the DataflowConstProp pass to handle propagation of discriminants. We handle this by adding 2 new variants to `TrackElem`: `TrackElem::Variant` for enum variants and `TrackElem::Discriminant` for the enum discriminant pseudo-place.

The difficulty is that the enum discriminant and enum variants may alias each another. This is the issue of the `Option<NonZeroUsize>` test, which is the equivalent of rust-lang/unsafe-code-guidelines#84 with a direct write.

To handle that, we generalize the flood process to flood all the potentially aliasing places. In particular:
- any write to `(PLACE as Variant)`, either direct or through a projection, floods `(PLACE as OtherVariant)` for all other variants and `discriminant(PLACE)`;
- `SetDiscriminant(PLACE)` floods `(PLACE as Variant)` for each variant.

This implies that flooding is not hierarchical any more, and that an assignment to a non-tracked place may need to flood a tracked place. This is handled by `for_each_aliasing_place` which generalizes `preorder_invoke`.

As we deaggregate enums by putting `SetDiscriminant` last, this allows to propagate the value of the discriminant.

This refactor will allow to make rust-lang#107009 able to handle discriminants too.

…rister

Fix unintentional UB in ui tests

`@matthiaskrgr` found UB in a bunch of the ui tests. This PR fixes a batch of miscellaneous tests I didn't think needed reviewers from a particular part of the project.

…mpiler-errors

Avoid ICE when the generic_span is empty

Fixes rust-lang#107998
r? `@TaKO8Ki`

…orkingjubilee

Shrink size of array benchmarks

Might've overdone it with the size of these benchmarks, as there's no need for them to be quite as large.

Fixes rust-lang#108011