- the self type includes some local type; and,
- type parameters in the self type must be constrained by a local type.
A type parameter is called *constrained* if it appears in some type-parameter of a local type.
Here are some examples that are accepted. In all of these examples, I
assume that `Foo` is a trait defined in another crate. If `Foo` were
defined in the local crate, then all the examples would be legal.
- `impl Foo for LocalType`
- `impl<T> Foo<T> for LocalType` -- T does not appear in Self, so it is OK
- `impl<T> Foo<T> for LocalType<T>` -- T here is constrained by LocalType
- `impl<T> Foo<T> for (LocalType<T>, T)` -- T here is constrained by LocalType
Here are some illegal examples (again, these examples assume that
`Foo` is not local to the current crate):
- `impl Foo for int` -- the Self type is not local
- `impl<T> Foo for T` -- T appears in Self unconstrained by a local type
- `impl<T> Foo for (LocalType, T)` -- T appears in Self unconstrained by a local type
This is a [breaking-change]. For the time being, you can opt out of
the new rules by placing `#[old_orphan_check]` on the trait (and
enabling the feature gate where the trait is defined). Longer term,
you should restructure your traits to avoid the problem. Usually this
means changing the order of parameters so that the "central" type
parameter is in the `Self` position.
As an example of that refactoring, consider the `BorrowFrom` trait:
```rust
pub trait BorrowFrom<Sized? Owned> for Sized? {
fn borrow_from(owned: &Owned) -> &Self;
}
```
As defined, this trait is commonly implemented for custom pointer
types, such as `Arc`. Those impls follow the pattern:
```rust
impl<T> BorrowFrom<Arc<T>> for T {...}
```
Unfortunately, this impl is illegal because the self type `T` is not
local to the current crate. Therefore, we are going to change the order of the parameters,
so that `BorrowFrom` becomes `Borrow`:
```rust
pub trait Borrow<Sized? Borrowed> for Sized? {
fn borrow_from(owned: &Self) -> &Borrowed;
}
```
Now the `Arc` impl is written:
```rust
impl<T> Borrow<T> for Arc<T> { ... }
```
This impl is legal because the self type (`Arc<T>`) is local.
Use autoderef for call notation. This is consistent in that we now autoderef all postfix operators (`.`, `[]`, and `()`). It also means you can call closures without writing `(*f)()`. Note that this is rebased atop the rollup, so only the final commit is relevant.
r? @pcwalton
After 8b3c67690c4747b9fadfef407e6261524fb03f8a the `make install`
command fails if docs are not disabled through CFG_DISABLE_DOCS,
because now the `install` target uses
../../tmp/dist/$(DOC_PKG_NAME)-$(CFG_BUILD)/install.sh
Instead of explicitly depending on
dist/$(PKG_NAME)-$(CFG_BUILD).tar.gz, the `prepare_[un]install`
targets now depend on `dist-tar-bins`, which packages the appropriate
dist archives depending on the configuration.
This removes a large array of deprecated functionality, regardless of how
recently it was deprecated. The purpose of this commit is to clean out the
standard libraries and compiler for the upcoming alpha release.
Some notable compiler changes were to enable warnings for all now-deprecated
command line arguments (previously the deprecated versions were silently
accepted) as well as removing deriving(Zero) entirely (the trait was removed).
The distribution no longer contains the libtime or libregex_macros crates. Both
of these have been deprecated for some time and are available externally.
This removes a large array of deprecated functionality, regardless of how
recently it was deprecated. The purpose of this commit is to clean out the
standard libraries and compiler for the upcoming alpha release.
Some notable compiler changes were to enable warnings for all now-deprecated
command line arguments (previously the deprecated versions were silently
accepted) as well as removing deriving(Zero) entirely (the trait was removed).
The distribution no longer contains the libtime or libregex_macros crates. Both
of these have been deprecated for some time and are available externally.
closes#20486closes#20474closes#20441
[breaking-change]
The `Index[Mut]` traits now have one less input parameter, as the return type of the indexing operation is an associated type. This breaks all existing implementations.
---
binop traits (`Add`, `Sub`, etc) now have an associated type for their return type. Also, the RHS input parameter now defaults to `Self` (except for the `Shl` and `Shr` traits). For example, the `Add` trait now looks like this:
``` rust
trait Add<Rhs=Self> {
type Output;
fn add(self, Rhs) -> Self::Output;
}
```
The `Neg` and `Not` traits now also have an associated type for their return type.
This breaks all existing implementations of these traits.
---
Affected traits:
- `Iterator { type Item }`
- `IteratorExt` no input/output types, uses `<Self as Iterator>::Item` in its methods
- `DoubleEndedIterator` no input/output types, uses `<Self as Iterator>::Item` in its methods
- `DoubleEndedIteratorExt` no input/output types, uses `<Self as Iterator>::Item` in its methods
- `RandomAccessIterator` no input/output types
- `ExactSizeIterator` no input/output types, uses `<Self as Iterator>::Item` in its methods
This breaks all the implementations of these traits.
Previously, the borrow mode of each upvar was inferred as part of regionck. This PR moves it into its own separate step. It also employs the `ExprUseVisitor`, further simplifying the code. The eventual goal is to support better inference of `Fn` vs `FnMut` vs `FnOnce` that is not based on the expected type, as well as supporting individual by-move upvars.
r? @eddyb
and which uses EUV. For now, upvar inference is not any smarter than
it ever was, but regionck is simpler because it doesn't have to do as
many things at once.
`UnboxedClosureTyper`. This requires adding a `tcx` field to
`ParameterEnvironment` but generally simplifies everything since we
only need to pass along an `UnboxedClosureTyper` or `Typer`.
