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`.
which should always result in an error.
NB. Some of the hunks in this commit rely on a later commit which adds
`tcx` into `param_env` and modifies `ParameterEnvironment` to
implement `Typer`.
expr-use-visitor) early. Turns out I was wrong to remove this; it
causes a lot of pain trying to run EUV etc during typeck without
ICEing on erroneous programs.
The `make_hash` function is used to prevent hashes of non-empty
buckets to collide with `EMPTY_HASH = 0u64`. Ideally this function
also preserve the uniform distribution of hashes and is cheap to
compute.
The new implementation reduces the input hash size by one bit, simply
by setting the most significant bit. This obviously prevent output
hashes to collide with `EMPTY_HASH` and guarantees that the uniform
distribution is preserved. Moreover, the new function is simpler (no
comparisons, just an OR) and (under the same assumptions as the old
function, i.e. only the least significant bit will contribute to the
bucket index) no additional collisions are caused.
