Tweak future opaque ty pretty printing
1. The `Return` type of a generator doesn't need to be a lang item just for diagnostic printing of types
2. We shouldn't suppress the `Output = Ty` of a opaque future if the type is a int or float var.
Initial implementation of return-position `impl Trait` in traits
* Create a new item kind, called `ImplTraitPlaceholder`, which is used to lower `ast::TyKind::ImplTrait` in trait method returns.
* This item is the child of the trait method, which simplifies the way we calculate bounds and stuff.
* Use the def-id of this type to construct a projection type that we use during astconv for the return type of the trait method signature.
* Implement logic to normalize this `ImplTraitPlaceholder` projection type when we know its concrete impl (this is pretty limited currently, but really there are no other selection candidates that make sense -- for now!)
* Check that the `impl Trait`'s bounds are satisfied on the concrete type provided in the impl.
This is obviously nowhere near complete, but I wanted to at least get some initial support landed so we can start playing around with it.
What works:
* async fn in trait and RPITIT, including multiple `impl Trait`s and `impl Trait` nested in associated type bindings, like `impl Future<Output = impl Sized>`
Reimplement `carrying_add` and `borrowing_sub` for signed integers.
As per the discussion in #85532, this PR reimplements `carrying_add` and `borrowing_sub` for signed integers.
It also adds unit tests for both unsigned and signed integers, emphasing on the behaviours of the methods.
Fix `range_{plus,minus}_one` bad suggestions
Fixes#9431.
The current `range_plus_one` and `range_minus_one` suggestions are completely incorrect when macros are involved.
This commit resolves this by disabling the lints for any range expression that is expanded from a macro. The reasons for this are that it is very difficult to create a correct suggestion in this case and that false negatives are less important for pedantic lints.
changelog: Fix `range_{plus,minus}_one` bad suggestions
Make `Debug` impl for `Term` useful
because `Term { ptr: 78942378998734298342, maker: PhantomData, }` does not excel at communicating the necessary information
rustdoc: remove unused CSS `div.impl-items > div`
This was added in 9077d540da to override the style on `<div>` tags that were acting as headers. These `<div>` tags were replaced with `<section>` tags in 32f62607c3, but this CSS was probably already redundant even then (the headers had already been replaced with real `<h3>` and `<h4>` tags in 76a3b609d0).
rustdoc: remove unused CSS `#implementations-list > h3 > span.in-band`
This was added in 51f26acaea to help with the display of an `<h3>` tag that has a `<span class='in-band'>` inside.
The way implementation lists were rendered was changed in 34bd2b845b to have `<code class='in-band'>`, making this CSS unused.
Then it was turned into a `<div>` in 9077d540da without issue.
Finally, the header itself acquired the `in-band` class in 76a3b609d0.
Normalize before erasing late-bound regions in `equal_up_to_regions`
Normalize erasing regions **first**, before passing the type through a `BottomUpFolder` which erases late-bound regions too.
The root cause of this issue is due to 96d4137dee, which removes a `normalize_erasing_regions` that happens before this call to `equal_up_to_regions`. While reverting that commit might be a fix, I think it was suspicious to be erasing late-bound regions first _then_ normalizing types in the first place in `equal_up_to_regions`.
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I am tempted to ask the reviewer to review and `r+` this without a UI test, since the existing issues that I think this fixes are all incredibly difficult to minimize (anything hyper/warp related, given the nature of those libraries 😓) or impossible to reproduce locally (the miri test), namely:
* This recently reported issue with tokio + warp: #101430
* This issue from `@RalfJung` about Miri being broken: #101344
* This additional issue reported in a comment by `@tmandry` (issue with fuchsia + hyper): https://github.com/rust-lang/rust/issues/101344#issuecomment-1235974564
I have locally verified that the repro in #101430 is fixed with this PR, but after a couple of hours of attempting to minimize this error and either failing to actually repro the ICE, or being overwhelmed with the number of traits and functions I need to inline into a UI test, I have basically given up. Thoughts are appreciated on how best to handle this.
r? `@oli-obk` who is at the intersection of MIR and types-related stuff who may be able to give advice 😅
