As mentioned in #29734, the range comparison closure can be improved.
The LLVM IR and the assembly from the new version are much simpler and
unfortunately we cannot rely on the compiler to optimise this much, as
it would need to know that `lo <= hi`.
Besides from simpler code, there might also be a performance
advantage, although it is unlikely to appear on benchmarks, as we are
doing a binary search, which should always involve few comparisons.
The code is available on the playpen for ease of comparison:
http://is.gd/4raMmH
`fs::File` was being referenced without either calling via `std::fs::File` or by using `File` after having used `std::fs::File`. Also `Path` was being referenced without first having used `std::path::Path`.
fs::File was being referenced without either calling via std::fs::File or by using File after having used fs::File. Also Path was being referenced without first having used std::path::Path.
This is not a fix to checks themselves per se (though we still use `Eq` MIR test instead of calling `PartialEq::eq`), but rather how we handle items we encounter in pattern position.
Previously we would just call `PartialEq` with the constant and the matchee, but now we essentially inline the constant instead. E.g. these two snippets are functionally equivalent at MIR level:
```
match val { Some(42) => true, _ => false }
```
and
```
const SECRET: Option<u8> = Some(42);
match val { SECRET => true, _ => false }
```
This approach also allows for more optimizations of matches. I.e. It can now exploit `SwitchInt` to switch on number inside a `Some` regardless of whether the value being an item or not.
This is based on @tsion’s already approved PR so I could reuse the file for more tests.
r? @eddyb
cc @nikomatsakis @tsion
These should probably be submitted upstream. They're inevitably going to
complicate merges, and because they're non-functional changes this just
isn't worth our time.
Obviously we can't remove the character one past the end of the String. And we can't today either - we'll just panic at char_at() instead - but if we're going to keep that assertion, we should at least have a correct assertion.
Obviously we can't remove the character one past the end of the String. And we can't today either - we'll just panic at char_at() instead - but if we're going to keep that assertion, we should at least have a correct assertion.
f64 methods have been stable since rust 1.0, but f32 never got stabilised.
I suggest backporting this to beta as well (needs changing stablilisation version then).
r? @aturon
Fixes https://github.com/rust-lang/rfcs/issues/1438
When looking in the documentation I often scan the examples the first thing I do. In these 3 cases it's not obvious which direction the operation happens by adding this comment it makes it more obvious.
r? @steveklabnik
Are trait impls still insta-stable? Considering that this design has been around for a long time on `String` and `OsString` it probably doesn't matter much...
The `From` impl is a bit strange to me. It's stolen from `OsString` but I'm not really sure about it... `String` just impls `From<&str>` instead, would that make more sense?
