Stop using `ty::GenericPredicates` for non-predicates_of queries
`GenericPredicates` is a struct of several parts: A list of of an item's own predicates, and a parent def id (and some effects related stuff, but ignore that since it's kinda irrelevant). When instantiating these generic predicates, it calls `predicates_of` on the parent and instantiates its predicates, and appends the item's own instantiated predicates too:
acb4e8b625/compiler/rustc_middle/src/ty/generics.rs (L407-L413)
Notice how this should result in a recursive set of calls to `predicates_of`... However, `GenericPredicates` is *also* misused by a bunch of *other* queries as a convenient way of passing around a list of predicates. For these queries, we don't ever set the parent def id of the `GenericPredicates`, but if we did, then this would be very easy to mistakenly call `predicates_of` instead of some other intended parent query.
Given that footgun, and the fact that we don't ever even *use* the parent def id in the `GenericPredicates` returned from queries like `explicit_super_predicates_of`, It really has no benefit over just returning `&'tcx [(Clause<'tcx>, Span)]`.
This PR additionally opts to wrap the results of `EarlyBinder`, as we've tended to use that in the return type of these kinds of queries to properly convey that the user has params to deal with, and it also gives a convenient way of iterating over a slice of things after instantiating.
Get rid of `predicates_defined_on`
This is the uncontroversial part of #129532. This simply inlines the `predicates_defined_on` into into `predicates_of`. Nothing should change here logically.
Cache supertrait outlives of impl header for soundness check
This caches the results of computing the transitive supertraits of an impl and filtering it to its outlives obligations. This is purely an optimization to improve https://github.com/rust-lang/rust/pull/124336.
Implement new effects desugaring
cc `@rust-lang/project-const-traits.` Will write down notes once I have finished.
* [x] See if we want `T: Tr` to desugar into `T: Tr, T::Effects: Compat<true>`
* [x] Fix ICEs on `type Assoc: ~const Tr` and `type Assoc<T: ~const Tr>`
* [ ] add types and traits to minicore test
* [ ] update rustc-dev-guide
Fixes#119717Fixes#123664Fixes#124857Fixes#126148
Provide suggestion to dereference closure tail if appropriate
When encoutnering a case like
```rust
use std::collections::HashMap;
fn main() {
let vs = vec![0, 0, 1, 1, 3, 4, 5, 6, 3, 3, 3];
let mut counts = HashMap::new();
for num in vs {
let count = counts.entry(num).or_insert(0);
*count += 1;
}
let _ = counts.iter().max_by_key(|(_, v)| v);
```
produce the following suggestion
```
error: lifetime may not live long enough
--> $DIR/return-value-lifetime-error.rs:13:47
|
LL | let _ = counts.iter().max_by_key(|(_, v)| v);
| ------- ^ returning this value requires that `'1` must outlive `'2`
| | |
| | return type of closure is &'2 &i32
| has type `&'1 (&i32, &i32)`
|
help: dereference the return value
|
LL | let _ = counts.iter().max_by_key(|(_, v)| **v);
| ++
```
Fix#50195.
When encoutnering a case like
```rust
//@ run-rustfix
use std::collections::HashMap;
fn main() {
let vs = vec![0, 0, 1, 1, 3, 4, 5, 6, 3, 3, 3];
let mut counts = HashMap::new();
for num in vs {
let count = counts.entry(num).or_insert(0);
*count += 1;
}
let _ = counts.iter().max_by_key(|(_, v)| v);
```
produce the following suggestion
```
error: lifetime may not live long enough
--> $DIR/return-value-lifetime-error.rs:13:47
|
LL | let _ = counts.iter().max_by_key(|(_, v)| v);
| ------- ^ returning this value requires that `'1` must outlive `'2`
| | |
| | return type of closure is &'2 &i32
| has type `&'1 (&i32, &i32)`
|
help: dereference the return value
|
LL | let _ = counts.iter().max_by_key(|(_, v)| **v);
| ++
```
Fix#50195.
