stabilize #[panic_handler]
closes#44489
### Update(2018-09-07)
This was proposed for stabilization in https://github.com/rust-lang/rust/issues/44489#issuecomment-398965881 and its FCP with disposition to merge / accept is nearly over. The summary of what's being stabilized can be found in https://github.com/rust-lang/rust/issues/44489#issuecomment-416645946
Documentation PRs:
- Reference. https://github.com/rust-lang-nursery/reference/pull/362
- Nomicon. https://github.com/rust-lang-nursery/nomicon/pull/75
---
`#[panic_implementation]` was implemented recently in #50338. `#[panic_implementation]` is basically the old `panic_fmt` language item but in a less error prone (\*) shape. There are still some issues and questions to sort out around this feature (cf. #44489) but this PR is meant to start a discussion about those issues / questions with the language team.
(\*) `panic_fmt` was not type checked; changes in its function signature caused serious, silent binary size regressions like the one observed in #43054
Some unresolved questions from #44489:
> Should the Display of PanicInfo format the panic information as "panicked at 'reason',
> src/main.rs:27:4", as "'reason', src/main.rs:27:4", or simply as "reason".
The current implementation formats `PanicInfo` as the first alternative, which is how panic messages are formatted by the `std` panic handler. The `Display` implementation is more than a convenience: `PanicInfo.message` is unstable so it's not possible to replicate the `Display` implementation on stable.
> Is this design compatible, or can it be extended to work, with unwinding implementations for
> no-std environments?
I believe @whitequark made more progress with unwinding in no-std since their last comment in #44489. Perhaps they can give us an update?
---
Another unresolved question is where this feature should be documented. The feature currently doesn't have any documentation.
cc @rust-lang/lang
cc @jackpot51 @alevy @phil-opp
* When encountering EOF, point at the last opening brace that does not
have the same indentation level as its close delimiter.
* When encountering the wrong type of close delimiter, point at the
likely correct open delimiter to give a better idea of what went
wrong.
refactor match guard
This is the first step to implement RFC 2294: if-let-guard. Tracking issue: https://github.com/rust-lang/rust/issues/51114
The second step should be introducing another variant `IfLet` in the Guard enum. I separated them into 2 PRs for the convenience of reviewers.
r? @petrochenkov
set cfg(rustdoc) when rustdoc is running on a crate
When using `#[doc(cfg)]` to document platform-specific items, it's a little cumbersome to get all the platforms' items to appear all at once. For example, the standard library adds `--cfg dox` to rustdoc's command line whenever it builds docs, and the documentation for `#![feature(doc_cfg)]` suggests using a Cargo feature to approximate the same thing. This is a little awkward, because you always need to remember to set `--features dox` whenever you build documentation.
This PR proposes making rustdoc set `#[cfg(rustdoc)]` whenever it runs on a crate, to provide an officially-sanctioned version of this that is set automatically. This way, there's a standardized way to declare that a certain version of an item is specifically when building docs.
To try to prevent the spread of this feature from happening too quickly, this PR also restricts the use of this flag to whenever `#![feature(doc_cfg)]` is active. I'm sure there are other uses for this, but right now i'm tying it to this feature. (If it makes more sense to give this its own feature, i can easily do that.)
Use FxHash{Map,Set} instead of the default Hash{Map,Set} everywhere in rustc.
Most of the compiler uses the `Fx` hasher but some places ended up with the default one.
Remove anonymous trait params from 2018 and beyond
cc @Centril @nikomatsakis
cc #41686rust-lang/rfcs#2522#53272
This PR removes support for anonymous trait parameters syntactically in rust 2018 and onward.
TODO:
- [x] Add tests
MIR: support user-given type annotations on fns, structs, and enums
This branch adds tooling to track user-given type annotations on functions, structs, and enum variant expressions. The user-given types are passed onto NLL which then enforces them.
cc #47184 — not a complete fix, as there are more cases to cover
r? @eddyb
cc @rust-lang/wg-compiler-nll
Use optimized SmallVec implementation
This PR replaces current SmallVec implementation with the one from the Servo project.
Closes https://github.com/rust-lang/rust/issues/51640
r? @Mark-Simulacrum
Feature gate where clauses on associated type impls
Fixes#52913. This doesn't address the core problem, which is tracked by https://github.com/rust-lang/rust/issues/47206. However, it fixes the stable-to-stable regression: you now have to enable `#![feature(generic_associated_types)]` to trigger the weird behaviour.
Allow panicking with string literal messages inside constants
r? @eddyb
cc https://github.com/rust-lang/rust/issues/51999
we can't implement things like `panic!("foo: {}", x)` right now because we can't call trait methods (most notably `Display::fmt`) inside constants. Also most of these impls probably have loops and conditions, so it's messy anyway.
But hey `panic!("foo")` works at least.
cc @japaric got any test ideas for `#![no_std]`?
