- Don't allow multiple default trait implementations
- Allow positive trait implementations just for structs and enums when
there's a default implementation for such trait.
Take 2. This PR includes a bunch of refactoring that was part of an experimental branch implementing [implied bounds]. That particular idea isn't ready to go yet, but the refactoring proved useful for fixing #22246. The implied bounds branch also exposed #22110 so a simple fix for that is included here. I still think some more refactoring would be a good idea here -- in particular I think most of the code in wf.rs is kind of duplicating the logic in implicator and should go, but I decided to post this PR and call it a day before diving into that. I'll write a bit more details about the solutions I adopted in the various bugs. I patched the two issues I was concerned about, which was the handling of supertraits and HRTB (the latter turned out to be fine, so I added a comment explaining why.)
r? @pnkfelix (for now, anyway)
cc @aturon
[implied bounds]: http://smallcultfollowing.com/babysteps/blog/2014/07/06/implied-bounds/
This commit stabilizes `std::borrow`, making the following modifications
to catch up the API with language changes:
* It renames `BorrowFrom` to `Borrow`, as was originally intended (but
blocked for technical reasons), and reorders the parameters
accordingly.
* It moves the type parameter of `ToOwned` to an associated type. This
is somewhat less flexible, in that each borrowed type must have a
unique owned type, but leads to a significant simplification for
`Cow`. Flexibility can be regained by using newtyped slices, which is
advisable for other reasons anyway.
* It removes the owned type parameter from `Cow`, making the type much
less verbose.
* Deprecates the `is_owned` and `is_borrowed` predicates in favor of
direct matching.
The above API changes are relatively minor; the basic functionality
remains the same, and essentially the whole module is now marked
`#[stable]`.
[breaking-change]
This commit is an implementation of [RFC 592][r592] and [RFC 840][r840]. These
two RFCs tweak the behavior of `CString` and add a new `CStr` unsized slice type
to the module.
[r592]: https://github.com/rust-lang/rfcs/blob/master/text/0592-c-str-deref.md
[r840]: https://github.com/rust-lang/rfcs/blob/master/text/0840-no-panic-in-c-string.md
The new `CStr` type is only constructable via two methods:
1. By `deref`'ing from a `CString`
2. Unsafely via `CStr::from_ptr`
The purpose of `CStr` is to be an unsized type which is a thin pointer to a
`libc::c_char` (currently it is a fat pointer slice due to implementation
limitations). Strings from C can be safely represented with a `CStr` and an
appropriate lifetime as well. Consumers of `&CString` should now consume `&CStr`
instead to allow producers to pass in C-originating strings instead of just
Rust-allocated strings.
A new constructor was added to `CString`, `new`, which takes `T: IntoBytes`
instead of separate `from_slice` and `from_vec` methods (both have been
deprecated in favor of `new`). The `new` method returns a `Result` instead of
panicking. The error variant contains the relevant information about where the
error happened and bytes (if present). Conversions are provided to the
`io::Error` and `old_io::IoError` types via the `FromError` trait which
translate to `InvalidInput`.
This is a breaking change due to the modification of existing `#[unstable]` APIs
and new deprecation, and more detailed information can be found in the two RFCs.
Notable breakage includes:
* All construction of `CString` now needs to use `new` and handle the outgoing
`Result`.
* Usage of `CString` as a byte slice now explicitly needs a `.as_bytes()` call.
* The `as_slice*` methods have been removed in favor of just having the
`as_bytes*` methods.
Closes#22469Closes#22470
[breaking-change]
This commit is an implementation of [RFC 823][rfc] which is another pass over
the `std::hash` module for stabilization. The contents of the module were not
entirely marked stable, but some portions which remained quite similar to the
previous incarnation are now marked `#[stable]`. Specifically:
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0823-hash-simplification.md
* `std::hash` is now stable (the name)
* `Hash` is now stable
* `Hash::hash` is now stable
* `Hasher` is now stable
* `SipHasher` is now stable
* `SipHasher::new` and `new_with_keys` are now stable
* `Hasher for SipHasher` is now stable
* Many `Hash` implementations are now stable
All other portions of the `hash` module remain `#[unstable]` as they are less
commonly used and were recently redesigned.
This commit is a breaking change due to the modifications to the `std::hash` API
and more details can be found on the [RFC][rfc].
Closes#22467
[breaking-change]
The big change here is that we update the object-safety rules to prohibit references to `Self` in the supertrait listing. See #22040 for the motivation. The other change is to handle the interaction of defaults that reference `Self` and object types (where `Self` is erased). We force users to give an explicit type in that scenario.
r? @aturon
