Don't allow upcasting to a supertype in the type of the match discriminant. Fixes#23116.
This is a [breaking-change] in that it closes a type hole that previously existed.
r? @pnkfelix
This commit:
* Introduces `std::convert`, providing an implementation of
RFC 529.
* Deprecates the `AsPath`, `AsOsStr`, and `IntoBytes` traits, all
in favor of the corresponding generic conversion traits.
Consequently, various IO APIs now take `AsRef<Path>` rather than
`AsPath`, and so on. Since the types provided by `std` implement both
traits, this should cause relatively little breakage.
* Deprecates many `from_foo` constructors in favor of `from`.
* Changes `PathBuf::new` to take no argument (creating an empty buffer,
as per convention). The previous behavior is now available as
`PathBuf::from`.
* De-stabilizes `IntoCow`. It's not clear whether we need this separate trait.
Closes#22751Closes#14433
[breaking-change]
impls.
This requires:
1. modifying trait selection a bit so that when we synthesize impls for
fn pointers and closures;
2. adding code to trans so that we can synthesize a `FnMut`/`FnOnce`
impl for a `Fn` closure and so forth.
contains ref-bindings, do not permit any upcasting from the type of
the value being matched. Similarly, do not permit coercion in a `let`.
This is a [breaking-change] in that it closes a type hole that
previously existed, and in that coercion is not performed. You should
be able to work around the latter by converting:
```rust
let ref mut x: T = expr;
```
into
```rust
let x: T = expr;
let ref mut x = x;
```
Restricting coercion not to apply in the case of `let ref` or `let ref mut` is sort
of unexciting to me, but seems the best solution:
1. Mixing coercion and `let ref` or `let ref mut` is a bit odd, because you are taking
the address of a (coerced) temporary, but only sometimes. It's not syntactically evident,
in other words, what's going on. When you're doing a coercion, you're kind of
2. Put another way, I would like to preserve the relationship that
`equality <= subtyping <= coercion <= as-coercion`, where this is
an indication of the number of `(T1,T2)` pairs that are accepted by
the various relations. Trying to mix `let ref mut` and coercion
would create another kind of relation that is like coercion, but
acts differently in the case where a precise match is needed.
3. In any case, this is strictly more conservative than what we had
before and we can undo it in the future if we find a way to make
coercion mix with type equality.
The change to match I feel ok about but similarly unthrilled. There is
some subtle text already concerning whether to use eqtype or subtype
for identifier bindings. The best fix I think would be to always have
match use strict equality but use subtyping on identifier bindings,
but the comment `(*)` explains why that's not working at the moment.
As above, I think we can change this as we clean up the code there.
This should solve issues #23115, #23469, and #23407.
As the title says, this is just a workaround. The underlying problem is that macro expansion can produce invalid spans. I've opened issue #23480 so we don't forget about that.
This commit clarifies some of the unstable features in the `str` module by
moving them out of the blanket `core` and `collections` features.
The following methods were moved to the `str_char` feature which generally
encompasses decoding specific characters from a `str` and dealing with the
result. It is unclear if any of these methods need to be stabilized for 1.0 and
the most conservative route for now is to continue providing them but to leave
them as unstable under a more specific name.
* `is_char_boundary`
* `char_at`
* `char_range_at`
* `char_at_reverse`
* `char_range_at_reverse`
* `slice_shift_char`
The following methods were moved into the generic `unicode` feature as they are
specifically enabled by the `unicode` crate itself.
* `nfd_chars`
* `nfkd_chars`
* `nfc_chars`
* `graphemes`
* `grapheme_indices`
* `width`
Safe fns are no longer subtypes of unsafe fns, but you can coerce from one to the other.
This is a [breaking-change] in that impl fns must now be declared `unsafe` if the trait is declared `unsafe`. In some rare cases, the subtyping change may also direct affect you, but no such cases were encountered in practice.
Fixes#23449.
r? @nrc
This commit clarifies some of the unstable features in the `str` module by
moving them out of the blanket `core` and `collections` features.
The following methods were moved to the `str_char` feature which generally
encompasses decoding specific characters from a `str` and dealing with the
result. It is unclear if any of these methods need to be stabilized for 1.0 and
the most conservative route for now is to continue providing them but to leave
them as unstable under a more specific name.
* `is_char_boundary`
* `char_at`
* `char_range_at`
* `char_at_reverse`
* `char_range_at_reverse`
* `slice_shift_char`
The following methods were moved into the generic `unicode` feature as they are
specifically enabled by the `unicode` crate itself.
* `nfd_chars`
* `nfkd_chars`
* `nfc_chars`
* `graphemes`
* `grapheme_indices`
* `width`
This upcast coercion currently never requires vtable changes. It should be generalized.
This is a [breaking-change] -- if you have an impl on an object type like `impl SomeTrait`, then this will no longer be applicable to object types like `SomeTrait+Send`. In the standard library, this primarily affected `Any`, and this PR adds impls for `Any+Send` as to keep the API the same in practice. An alternate workaround is to use UFCS form or standalone fns. For more details, see <https://github.com/rust-lang/rust/issues/18737#issuecomment-78450798>.
r? @nrc
This upcast coercion currently preserves the vtable for the object, but
eventually it can be used to create a derived vtable. The upcast
coercion is not introduced into method dispatch; see comment on #18737
for information about why. Fixes#18737.
This removes the error case of the compression functions, the only errors that
can occur are incorrect parameters or an out-of-memory condition, both of which
are handled with panics in Rust.
Also introduces an extensible `Error` type instead of returning an `Option`.
The type implements a destructor so you can't destructure it.
This removes the error case of the compression functions, the only errors that
can occur are incorrect parameters or an out-of-memory condition, both of which
are handled with panics in Rust.
Also introduces an extensible `Error` type instead of returning an `Option`.
This commit deprecates the `count`, `range` and `range_step` functions
in `iter`, in favor of range notation. To recover all existing
functionality, a new `step_by` adapter is provided directly on `ops::Range`
and `ops::RangeFrom`.
[breaking-change]
r? @alexcrichton
It wasn't clear to me that early_error was correct here, but it seems to
work. This code is reachable from `rustdoc`, which is problematic, because
early_error panics. rustc handles the panics gracefully (without ICEing or
crashing), but rustdoc does not. It's not the first such rustdoc problem,
though:
$ rustdoc hello.rs --extern std=bad-std
error: extern location for std does not exist: bad-std
hello.rs:1:1: 1:1 error: can't find crate for `std`
hello.rs:1
^
error: aborting due to 2 previous errors
thread '<unnamed>' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:151
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: "rustc failed"', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libcore/result.rs:744
thread '<main>' panicked at 'child thread None panicked', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/thread.rs:661
This commit deprecates the `count`, `range` and `range_step` functions
in `iter`, in favor of range notation. To recover all existing
functionality, a new `step_by` adapter is provided directly on `ops::Range`
and `ops::RangeFrom`.
[breaking-change]
The new `std::io` module has had some time to bake now, and this commit
stabilizes its functionality. There are still portions of the module which
remain unstable, and below contains a summart of the actions taken.
This commit also deprecates the entire contents of the `old_io` module in a
blanket fashion. All APIs should now have a reasonable replacement in the
new I/O modules.
Stable APIs:
* `std::io` (the name)
* `std::io::prelude` (the name)
* `Read`
* `Read::read`
* `Read::{read_to_end, read_to_string}` after being modified to return a `usize`
for the number of bytes read.
* `ReadExt`
* `Write`
* `Write::write`
* `Write::{write_all, write_fmt}`
* `WriteExt`
* `BufRead`
* `BufRead::{fill_buf, consume}`
* `BufRead::{read_line, read_until}` after being modified to return a `usize`
for the number of bytes read.
* `BufReadExt`
* `BufReader`
* `BufReader::{new, with_capacity}`
* `BufReader::{get_ref, get_mut, into_inner}`
* `{Read,BufRead} for BufReader`
* `BufWriter`
* `BufWriter::{new, with_capacity}`
* `BufWriter::{get_ref, get_mut, into_inner}`
* `Write for BufWriter`
* `IntoInnerError`
* `IntoInnerError::{error, into_inner}`
* `{Error,Display} for IntoInnerError`
* `LineWriter`
* `LineWriter::{new, with_capacity}` - `with_capacity` was added
* `LineWriter::{get_ref, get_mut, into_inner}` - `get_mut` was added)
* `Write for LineWriter`
* `BufStream`
* `BufStream::{new, with_capacities}`
* `BufStream::{get_ref, get_mut, into_inner}`
* `{BufRead,Read,Write} for BufStream`
* `stdin`
* `Stdin`
* `Stdin::lock`
* `Stdin::read_line` - added method
* `StdinLock`
* `Read for Stdin`
* `{Read,BufRead} for StdinLock`
* `stdout`
* `Stdout`
* `Stdout::lock`
* `StdoutLock`
* `Write for Stdout`
* `Write for StdoutLock`
* `stderr`
* `Stderr`
* `Stderr::lock`
* `StderrLock`
* `Write for Stderr`
* `Write for StderrLock`
* `io::Result`
* `io::Error`
* `io::Error::last_os_error`
* `{Display, Error} for Error`
Unstable APIs:
(reasons can be found in the commit itself)
* `Write::flush`
* `Seek`
* `ErrorKind`
* `Error::new`
* `Error::from_os_error`
* `Error::kind`
Deprecated APIs
* `Error::description` - available via the `Error` trait
* `Error::detail` - available via the `Display` implementation
* `thread::Builder::{stdout, stderr}`
Changes in functionality:
* `old_io::stdio::set_stderr` is now a noop as the infrastructure for printing
backtraces has migrated to `std::io`.
[breaking-change]
