Lazily normalize inside trait ref during orphan check & consider ty params in rigid alias types to be uncovered
Fixes#99554, fixesrust-lang/types-team#104.
Fixes#114061.
Supersedes #100555.
Tracking issue for the future compatibility lint: #124559.
r? lcnr
Change leak check and suspicious auto trait lint warning messages
The leak check lint message "this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!" is misleading as some cases may not be phased out and could end being accepted. This is under discussion still.
The suspicious auto trait lint the change in behavior already happened, so the new message is probably more accurate.
r? `@lcnr`
Closes#93367
deduplicate infer var instantiation
Having 3 separate implementations of one of the most subtle parts of our type system is not a good strategy if we want to maintain a sound type system ✨ while working on this I already found some subtle bugs in the existing code, so that's awesome 🎉 cc #121159
This was necessary as I am not confident in my nll changes in #119106, so I am first cleaning this up in a separate PR.
r? `@BoxyUwU`
Stop bailing out from compilation just because there were incoherent traits
fixes#120343
but also has a lot of "type annotations needed" fallout. Some are fixed in the second commit.
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.
Make regionck care about placeholders in outlives components
Currently, we don't consider a placeholder type `!T` to be a type component when it comes to processing type-outlives obligations. This means that they are essentially treated like unit values with no sub-components, and always outlive any region. This is problematic for `non_lifetime_binders`, and even more problematic for `with_negative_coherence`, since negative coherence uses placeholders as universals.
This PR adds `Component::Placeholder` which acts much like `Component::Param`. This currently causes a regression in some non-lifetime-binders tests because `for<T> T: 'static` doesn't imply itself when processing outlives obligations, so code like this will fail:
```
fn foo() where for<T> T: 'static {
foo() //~ fails
}
```
Since the where clause doesn't imply itself. This requires making the `MatchAgainstHigherRankedOutlives` relation smarter when it comes to binders.
r? types
