That is, when offering suggestions for unresolved method calls, avoid
suggesting traits for which implementing the trait for the receiver type
either makes little sense (e.g. type errors, or sugared unboxed
closures), or violates coherence.
The latter is approximated by ensuring that at least one of `{receiver
type, trait}` is local. This isn't precisely correct due to
multidispatch, but the error messages one encounters in such situation
are useless more often than not; it is better to be conservative and
miss some cases, than have overly many false positives (e.g. writing
`some_slice.map(|x| ...)` uselessly suggested that one should implement
`IteratorExt` for `&[T]`, while the correct fix is to call `.iter()`).
Closes#21420.
That is, when offering suggestions for unresolved method calls, avoid
suggesting traits for which implementing the trait for the receiver type
either makes little sense (e.g. type errors, or sugared unboxed
closures), or violates coherence.
The latter is approximated by ensuring that at least one of `{receiver
type, trait}` is local. This isn't precisely correct due to
multidispatch, but the error messages one encounters in such situation
are useless more often than not; it is better to be conservative and
miss some cases, than have overly many false positives (e.g. writing
`some_slice.map(|x| ...)` uselessly suggested that one should implement
`IteratorExt` for `&[T]`, while the correct fix is to call `.iter()`).
Closes#21420.
This commits adds an associated type to the `FromStr` trait representing an
error payload for parses which do not succeed. The previous return value,
`Option<Self>` did not allow for this form of payload. After the associated type
was added, the following attributes were applied:
* `FromStr` is now stable
* `FromStr::Err` is now stable
* `FromStr::from_str` is now stable
* `StrExt::parse` is now stable
* `FromStr for bool` is now stable
* `FromStr for $float` is now stable
* `FromStr for $integral` is now stable
* Errors returned from stable `FromStr` implementations are stable
* Errors implement `Display` and `Error` (both impl blocks being `#[stable]`)
Closes#15138
This commits adds an associated type to the `FromStr` trait representing an
error payload for parses which do not succeed. The previous return value,
`Option<Self>` did not allow for this form of payload. After the associated type
was added, the following attributes were applied:
* `FromStr` is now stable
* `FromStr::Err` is now stable
* `FromStr::from_str` is now stable
* `StrExt::parse` is now stable
* `FromStr for bool` is now stable
* `FromStr for $float` is now stable
* `FromStr for $integral` is now stable
* Errors returned from stable `FromStr` implementations are stable
* Errors implement `Display` and `Error` (both impl blocks being `#[stable]`)
Closes#15138
This commit aims to stabilize the `TypeId` abstraction by moving it out of the
`intrinsics` module into the `any` module of the standard library. Specifically,
* `TypeId` is now defined at `std::any::TypeId`
* `TypeId::hash` has been removed in favor of an implementation of `Hash`.
This commit also performs a final pass over the `any` module, confirming the
following:
* `Any::get_type_id` remains unstable as *usage* of the `Any` trait will likely
never require this, and the `Any` trait does not need to be implemented for
any other types. As a result, this implementation detail can remain unstable
until associated statics are implemented.
* `Any::downcast_ref` is now stable
* `Any::downcast_mut` is now stable
* `BoxAny` remains unstable. While a direct impl on `Box<Any>` is allowed today
it does not allow downcasting of trait objects like `Box<Any + Send>` (those
returned from `Thread::join`). This is covered by #18737.
* `BoxAny::downcast` is now stable.
Loading methods from external crates was erroneously using the type's privacy
for each method instead of each method's privacy. This commit fixes that.
Closes#21202
This commit also moves privacy to its own crate because I thought that was where the bug was. Turns out it wasn't, but it helped me iterate at least!
For a call like `foo.bar()` where the method `bar` can't be resolved,
the compiler will search for traits that have methods with name `bar` to
give a more informative error, providing a list of possibilities.
Closes#7643.
Loading methods from external crates was erroneously using the type's privacy
for each method instead of each method's privacy. This commit fixes that.
Closes#21202
If `a.method();` can't be resolved, we first look for implemented traits
globally and suggest those. If there are no such traits found, we only
then fall back to suggesting from the unfiltered list of traits.
For a call like `foo.bar()` where the method `bar` can't be resolved,
the compiler will search for traits that have methods with name `bar` to
give a more informative error, providing a list of possibilities.
Closes#7643.
This gets rid of the 'experimental' level, removes the non-staged_api
case (i.e. stability levels for out-of-tree crates), and lets the
staged_api attributes use 'unstable' and 'deprecated' lints.
This makes the transition period to the full feature staging design
a bit nicer.
This commit takes a first pass at stabilizing `std::thread`:
* It removes the `detach` method in favor of two constructors -- `spawn`
for detached threads, `scoped` for "scoped" (i.e., must-join)
threads. This addresses some of the surprise/frustrating debug
sessions with the previous API, in which `spawn` produced a guard that
on destruction joined the thread (unless `detach` was called).
The reason to have the division in part is that `Send` will soon not
imply `'static`, which means that `scoped` thread creation can take a
closure over *shared stack data* of the parent thread. On the other
hand, this means that the parent must not pop the relevant stack
frames while the child thread is running. The `JoinGuard` is used to
prevent this from happening by joining on drop (if you have not
already explicitly `join`ed.) The APIs around `scoped` are
future-proofed for the `Send` changes by taking an additional lifetime
parameter. With the current definition of `Send`, this is forced to be
`'static`, but when `Send` changes these APIs will gain their full
flexibility immediately.
Threads that are `spawn`ed, on the other hand, are detached from the
start and do not yield an RAII guard.
The hope is that, by making `scoped` an explicit opt-in with a very
suggestive name, it will be drastically less likely to be caught by a
surprising deadlock due to an implicit join at the end of a scope.
* The module itself is marked stable.
* Existing methods other than `spawn` and `scoped` are marked stable.
The migration path is:
```rust
Thread::spawn(f).detached()
```
becomes
```rust
Thread::spawn(f)
```
while
```rust
let res = Thread::spawn(f);
res.join()
```
becomes
```rust
let res = Thread::scoped(f);
res.join()
```
[breaking-change]
fmt::Show is for debugging, and can and should be implemented for
all public types. This trait is used with `{:?}` syntax. There still
exists #[derive(Show)].
fmt::String is for types that faithfully be represented as a String.
Because of this, there is no way to derive fmt::String, all
implementations must be purposeful. It is used by the default format
syntax, `{}`.
This will break most instances of `{}`, since that now requires the type
to impl fmt::String. In most cases, replacing `{}` with `{:?}` is the
correct fix. Types that were being printed specifically for users should
receive a fmt::String implementation to fix this.
Part of #20013
[breaking-change]
