This PR aims to improve the readability of diagnostic messages that involve unresolved type variables. Currently, messages like the following:
```rust
mismatched types: expected `core::result::Result<uint,()>`, found `core::option::Option<<generic #1>>`
<anon>:6 let a: Result<uint, ()> = None;
^~~~
mismatched types: expected `&mut <generic #2>`, found `uint`
<anon>:7 f(42u);
^~~
```
tend to appear unapproachable to new users. [0] While specific type var IDs are valuable in
diagnostics that deal with more than one such variable, in practice many messages
only mention one. In those cases, leaving out the specific number makes the messages
slightly less terrifying.
```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_>`
<anon>:6 let a: Result<uint, ()> = None;
^~~~
mismatched types: expected `&mut _`, found `uint`
<anon>:7 f(42u);
^~~
```
As you can see, I also tweaked the aesthetics slightly by changing type variables to use the type hole syntax _. For integer variables, the syntax used is:
```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_#1i>`
<anon>:6 let a: Result<uint, ()> = Some(1);
```
and float variables:
```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_#1f>`
<anon>:6 let a: Result<uint, ()> = Some(0.5);
```
[0] https://twitter.com/coda/status/517713085465772032
Closes https://github.com/rust-lang/rust/issues/2632.
Closes https://github.com/rust-lang/rust/issues/3404.
Closes https://github.com/rust-lang/rust/issues/18426.
The error messages still aren’t as good as they were before DST, but they better
describe the actual problem, not mentioning `Sized` at all (because that bound
is normally implied, not explicitly stated).
Closes#17567.
Closes#18040.
Closes#18159.
This commit adds the following impls:
impl<T> Deref<[T]> for Vec<T>
impl<T> DerefMut<[T]> for Vec<T>
impl Deref<str> for String
This commit also removes all duplicated inherent methods from vectors and
strings as implementations will now silently call through to the slice
implementation. Some breakage occurred at std and beneath due to inherent
methods removed in favor of those in the slice traits and std doesn't use its
own prelude,
cc #18424
This common representation for delimeters should make pattern matching easier. Having a separate `token::DelimToken` enum also allows us to enforce the invariant that the opening and closing delimiters must be the same in `ast::TtDelimited`, removing the need to ensure matched delimiters when working with token trees.
This includes updating the language items and marking what needs to
change after a snapshot.
If you do not use the standard library, the language items you need to
implement have changed. For example:
```rust
#[lang = "fail_fmt"] fn fail_fmt() -> ! { loop {} }
```
is now
```rust
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
```
Related, lesser-implemented language items `fail` and
`fail_bounds_check` have become `panic` and `panic_bounds_check`, as
well. These are implemented by `libcore`, so it is unlikely (though
possible!) that these two renamings will affect you.
[breaking-change]
Fix test suite
https://github.com/rust-lang/rfcs/pull/221
The current terminology of "task failure" often causes problems when
writing or speaking about code. You often want to talk about the
possibility of an operation that returns a Result "failing", but cannot
because of the ambiguity with task failure. Instead, you have to speak
of "the failing case" or "when the operation does not succeed" or other
circumlocutions.
Likewise, we use a "Failure" header in rustdoc to describe when
operations may fail the task, but it would often be helpful to separate
out a section describing the "Err-producing" case.
We have been steadily moving away from task failure and toward Result as
an error-handling mechanism, so we should optimize our terminology
accordingly: Result-producing functions should be easy to describe.
To update your code, rename any call to `fail!` to `panic!` instead.
Assuming you have not created your own macro named `panic!`, this
will work on UNIX based systems:
grep -lZR 'fail!' . | xargs -0 -l sed -i -e 's/fail!/panic!/g'
You can of course also do this by hand.
[breaking-change]
This is a large spring-cleaning commit now that the 0.12.0 release has passed removing an amount of deprecated functionality. This removes a number of deprecated crates (all still available as cargo packages in the rust-lang organization) as well as a slew of deprecated functions. All `#[crate_id]` support has also been removed.
I tried to avoid anything that was recently deprecated, but I may have missed something! The major pain points of this commit is the fact that rustc/syntax have `#[allow(deprecated)]`, but I've removed that annotation so moving forward they should be cleaned up as we go.
