Add diagnostics for mistyped inclusive range
Inclusive ranges are correctly typed as `..=`. However, it's quite easy to think of it as being like `==`, and type `..==` instead. This PR adds helpful diagnostics for this case.
Resolves#86395 (there are some other cases there, but I think those should probably have separate issues).
r? `@estebank`
Stabilize "RangeFrom" patterns in 1.55
Implements a partial stabilization of #67264 and #37854.
Reference PR: https://github.com/rust-lang/reference/pull/900
# Stabilization Report
This stabilizes the `X..` pattern, shown as such, offering an exhaustive match for unsigned integers:
```rust
match x as u32 {
0 => println!("zero!"),
1.. => println!("positive number!"),
}
```
Currently if a Rust author wants to write such a match on an integer, they must use `1..={integer}::MAX` . By allowing a "RangeFrom" style pattern, this simplifies the match to not require the MAX path and thus not require specifically repeating the type inside the match, allowing for easier refactoring. This is particularly useful for instances like the above case, where different behavior on "0" vs. "1 or any positive number" is desired, and the actual MAX is unimportant.
Notably, this excepts slice patterns which include half-open ranges from stabilization, as the wisdom of those is still subject to some debate.
## Practical Applications
Instances of this specific usage have appeared in the compiler:
16143d1067/compiler/rustc_middle/src/ty/inhabitedness/mod.rs (L219)673d0db5e3/compiler/rustc_ty_utils/src/ty.rs (L524)
And I have noticed there are also a handful of "in the wild" users who have deployed it to similar effect, especially in the case of rejecting any value of a certain number or greater. It simply makes it much more ergonomic to write an irrefutable match, as done in Katholieke Universiteit Leuven's [SCALE and MAMBA project](05e5db00d5/WebAssembly/scale_std/src/fixed_point.rs (L685-L695)).
## Tests
There were already many tests in [src/test/ui/half-open-range/patterns](90a2e5e3fe/src/test/ui/half-open-range-patterns), as well as [generic pattern tests that test the `exclusive_range_pattern` feature](673d0db5e3/src/test/ui/pattern/usefulness/integer-ranges/reachability.rs), many dating back to the feature's introduction and remaining standing to this day. However, this stabilization comes with some additional tests to explore the... sometimes interesting behavior of interactions with other patterns. e.g. There is, at least, a mild diagnostic improvement in some edge cases, because before now, the pattern `0..=(5+1)` encounters the `half_open_range_patterns` feature gate and can thus emit the request to enable the feature flag, while also emitting the "inclusive range with no end" diagnostic. There is no intent to allow an `X..=` pattern that I am aware of, so removing the flag request is a strict improvement. The arrival of the `J | K` "or" pattern also enables some odd formations.
Some of the behavior tested for here is derived from experiments in this [Playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=58777b3c715c85165ac4a70d93efeefc) example, linked at https://github.com/rust-lang/rust/issues/67264#issuecomment-812770692, which may be useful to reference to observe the current behavior more closely.
In addition tests constituting an explanation of the "slicing range patterns" syntax issue are included in this PR.
## Desiderata
The exclusive range patterns and half-open range patterns are fairly strongly requested by many authors, as they make some patterns much more natural to write, but there is disagreement regarding the "closed" exclusive range pattern or the "RangeTo" pattern, especially where it creates "off by one" gaps in the presence of a "catch-all" wildcard case. Also, there are obviously no range analyses in place that will force diagnostics for e.g. highly overlapping matches. I believe these should be warned on, ideally, and I think it would be reasonable to consider such a blocker to stabilizing this feature, but there is no technical issue with the feature as-is from the purely syntactic perspective as such overlapping or missed matches can already be generated today with such a catch-all case. And part of the "point" of the feature, at least from my view, is to make it easier to omit wildcard matches: a pattern with such an "open" match produces an irrefutable match and does not need the wild card case, making it easier to benefit from exhaustiveness checking.
## History
- Implemented:
- Partially via exclusive ranges: https://github.com/rust-lang/rust/pull/35712
- Fully with half-open ranges: https://github.com/rust-lang/rust/pull/67258
- Unresolved Questions:
- The precedence concerns of https://github.com/rust-lang/rust/pull/48501 were considered as likely requiring adjustment but probably wanting a uniform consistent change across all pattern styles, given https://github.com/rust-lang/rust/issues/67264#issuecomment-720711656, but it is still unknown what changes might be desired
- How we want to handle slice patterns in ranges seems to be an open question still, as witnessed in the discussion of this PR!
I checked but I couldn't actually find an RFC for this, and given "approved provisionally by lang team without an RFC", I believe this might require an RFC before it can land? Unsure of procedure here, on account of this being stabilizing a subset of a feature of syntax.
r? `@scottmcm`
Fix ICE when misplaced visibility cannot be properly parsed
Fixes#86895
The issue was that a failure to parse the visibility was causing the original error to be dropped before being emitted.
The resulting error isn't quite as nice as when the visibility is parsed properly, but I'm not sure which error to prioritize here. Displaying both errors might be too confusing.
r? ```@estebank```
Recover from `&dyn mut ...` parse errors
Consider this example:
```rust
fn main() {
let r: &dyn mut Trait;
}
```
This currently leads to:
```
error: expected one of `!`, `(`, `;`, `=`, `?`, `for`, lifetime, or path, found keyword `mut`
--> src/main.rs:2:17
|
2 | let r: &dyn mut Trait;
| ^^^ expected one of 8 possible tokens
error: aborting due to previous error
```
However, especially for beginners, I think it is easy to get `&dyn mut` and `&mut dyn` confused. With my changes, I get a help message, and the parser even recovers:
```
error: `mut` must precede `dyn`
--> test.rs:2:12
|
2 | let r: &dyn mut Trait;
| ^^^^^^^^ help: place `mut` before `dyn`: `&mut dyn`
error[E0405]: cannot find trait `Trait` in this scope
--> test.rs:2:21
|
2 | let r: &dyn mut Trait;
| ^^^^^ not found in this scope
error: aborting due to 2 previous errors
```
Remove unused dependencies from compiler crates
Various compiler crates have dependencies that they don't appear to use. I used some scripting to detect such dependencies, filtered them based on some manual review, and removed those that do indeed appear to be entirely unused.
Use HTTPS links where possible
While looking at #86583, I wondered how many other (insecure) HTTP links were in `rustc`. This changes most other `http` links to `https`. While most of the links are in comments or documentation, there are a few other HTTP links that are used by CI that are changed to HTTPS.
Notes:
- I didn't change any to or in licences
- Some links don't support HTTPS :(
- Some `http` links were dead, in those cases I upgraded them to their new places (all of which used HTTPS)
Re-add support for parsing (and pretty-printing) inner-attributes in match body
Re-add support for parsing (and pretty-printing) inner-attributes within body of a `match`.
In other words, we can do `match EXPR { #![inner_attr] ARM_1 ARM_2 ... }` again.
I believe this unbreaks the only four crates that crater flagged as broken by PR #83312.
(I am putting this up so that the lang-team can check it out and decide whether it changes their mind about what to do regarding PR #83312.)
Fix two ICEs in the parser
This pull request fixes#84104 and fixes#84148. The latter is caused by an invalid `assert_ne!()` in the parser, which I have simply removed because the error is then caught in another part of the parser.
#84104 is somewhat more subtle and has to do with a suggestion to remove extraneous `<` characters; for instance:
```rust
fn main() {
foo::<Ty<<<i32>();
}
```
currently leads to
```
error: unmatched angle brackets
--> unmatched-langle.rs:2:10
|
2 | foo::<Ty<<<i32>();
| ^^^ help: remove extra angle brackets
```
which is obviously wrong and stems from the fact that the code for issuing the above suggestion does not consider the possibility that there might be other tokens in between the opening angle brackets. In #84104, this has led to a span being generated that ends in the middle of a multi-byte character (because the code issuing the suggestion thought that it was only skipping over `<`, which are single-byte), causing an ICE.
Remove unused feature gates
The first commit removes a usage of a feature gate, but I don't expect it to be controversial as the feature gate was only used to workaround a limitation of rust in the past. (closures never being `Clone`)
The second commit uses `#[allow_internal_unstable]` to avoid leaking the `trusted_step` feature gate usage from inside the index newtype macro. It didn't work for the `min_specialization` feature gate though.
The third commit removes (almost) all feature gates from the compiler that weren't used anyway.
# Stabilization report
## Summary
This stabilizes using macro expansion in key-value attributes, like so:
```rust
#[doc = include_str!("my_doc.md")]
struct S;
#[path = concat!(env!("OUT_DIR"), "/generated.rs")]
mod m;
```
See the changes to the reference for details on what macros are allowed;
see Petrochenkov's excellent blog post [on internals](https://internals.rust-lang.org/t/macro-expansion-points-in-attributes/11455)
for alternatives that were considered and rejected ("why accept no more
and no less?")
This has been available on nightly since 1.50 with no major issues.
## Notes
### Accepted syntax
The parser accepts arbitrary Rust expressions in this position, but any expression other than a macro invocation will ultimately lead to an error because it is not expected by the built-in expression forms (e.g., `#[doc]`). Note that decorators and the like may be able to observe other expression forms.
### Expansion ordering
Expansion of macro expressions in "inert" attributes occurs after decorators have executed, analogously to macro expressions appearing in the function body or other parts of decorator input.
There is currently no way for decorators to accept macros in key-value position if macro expansion must be performed before the decorator executes (if the macro can simply be copied into the output for later expansion, that can work).
## Test cases
- https://github.com/rust-lang/rust/blob/master/src/test/ui/attributes/key-value-expansion-on-mac.rs
- https://github.com/rust-lang/rust/blob/master/src/test/rustdoc/external-doc.rs
The feature has also been dogfooded extensively in the compiler and
standard library:
- https://github.com/rust-lang/rust/pull/83329
- https://github.com/rust-lang/rust/pull/83230
- https://github.com/rust-lang/rust/pull/82641
- https://github.com/rust-lang/rust/pull/80534
## Implementation history
- Initial proposal: https://github.com/rust-lang/rust/issues/55414#issuecomment-554005412
- Experiment to see how much code it would break: https://github.com/rust-lang/rust/pull/67121
- Preliminary work to restrict expansion that would conflict with this
feature: https://github.com/rust-lang/rust/pull/77271
- Initial implementation: https://github.com/rust-lang/rust/pull/78837
- Fix for an ICE: https://github.com/rust-lang/rust/pull/80563
## Unresolved Questions
~~https://github.com/rust-lang/rust/pull/83366#issuecomment-805180738 listed some concerns, but they have been resolved as of this final report.~~
## Additional Information
There are two workarounds that have a similar effect for `#[doc]`
attributes on nightly. One is to emulate this behavior by using a limited version of this feature that was stabilized for historical reasons:
```rust
macro_rules! forward_inner_docs {
($e:expr => $i:item) => {
#[doc = $e]
$i
};
}
forward_inner_docs!(include_str!("lib.rs") => struct S {});
```
This also works for other attributes (like `#[path = concat!(...)]`).
The other is to use `doc(include)`:
```rust
#![feature(external_doc)]
#[doc(include = "lib.rs")]
struct S {}
```
The first works, but is non-trivial for people to discover, and
difficult to read and maintain. The second is a strange special-case for
a particular use of the macro. This generalizes it to work for any use
case, not just including files.
I plan to remove `doc(include)` when this is stabilized. The
`forward_inner_docs` workaround will still compile without warnings, but
I expect it to be used less once it's no longer necessary.
Recover from invalid `struct` item syntax
Parse unsupported "default field const values":
```rust
struct S {
field: Type = const_val,
}
```
Recover from small `:` typo and provide suggestion:
```rust
struct S {
field; Type,
field2= Type,
}
```
Fix `--remap-path-prefix` not correctly remapping `rust-src` component paths and unify handling of path mapping with virtualized paths
This PR fixes#73167 ("Binaries end up containing path to the rust-src component despite `--remap-path-prefix`") by preventing real local filesystem paths from reaching compilation output if the path is supposed to be remapped.
`RealFileName::Named` introduced in #72767 is now renamed as `LocalPath`, because this variant wraps a (most likely) valid local filesystem path.
`RealFileName::Devirtualized` is renamed as `Remapped` to be used for remapped path from a real path via `--remap-path-prefix` argument, as well as real path inferred from a virtualized (during compiler bootstrapping) `/rustc/...` path. The `local_path` field is now an `Option<PathBuf>`, as it will be set to `None` before serialisation, so it never reaches any build output. Attempting to serialise a non-`None` `local_path` will cause an assertion faliure.
When a path is remapped, a `RealFileName::Remapped` variant is created. The original path is preserved in `local_path` field and the remapped path is saved in `virtual_name` field. Previously, the `local_path` is directly modified which goes against its purpose of "suitable for reading from the file system on the local host".
`rustc_span::SourceFile`'s fields `unmapped_path` (introduced by #44940) and `name_was_remapped` (introduced by #41508 when `--remap-path-prefix` feature originally added) are removed, as these two pieces of information can be inferred from the `name` field: if it's anything other than a `FileName::Real(_)`, or if it is a `FileName::Real(RealFileName::LocalPath(_))`, then clearly `name_was_remapped` would've been false and `unmapped_path` would've been `None`. If it is a `FileName::Real(RealFileName::Remapped{local_path, virtual_name})`, then `name_was_remapped` would've been true and `unmapped_path` would've been `Some(local_path)`.
cc `@eddyb` who implemented `/rustc/...` path devirtualisation
Parse unsupported "default field const values":
```rust
struct S {
field: Type = const_val,
}
```
Recover from small `:` typo and provide suggestion:
```rust
struct S {
field; Type,
field2= Type,
}
```
In other words, we can do `match EXPR { #![inner_attr] ARM_1 ARM_2 ... }` again.
I believe this unbreaks the only four crates that crater flagged as broken by PR 83312.
(I am putting this up so that the lang-team can check it out and decide whether
it changes their mind about what to do regarding PR 83312.)
