Support registering inert attributes and attribute tools using crate-level attributes
And remove `#[feature(custom_attribute)]`.
(`rustc_plugin::Registry::register_attribute` is not removed yet, I'll do it in a follow up PR.)
```rust
#![register_attr(my_attr)]
#![register_tool(my_tool)]
#[my_attr] // OK
#[my_tool::anything] // OK
fn main() {}
```
---
Some tools (`rustfmt` and `clippy`) used in tool attributes are hardcoded in the compiler.
We need some way to introduce them without hardcoding as well.
This PR introduces a way to do it with a crate level attribute.
The previous attempt to introduce them through command line (https://github.com/rust-lang/rust/pull/57921) met some resistance.
This probably needs to go through an RFC before stabilization.
However, I'd prefer to land *this* PR without an RFC to able to remove `#[feature(custom_attribute)]` and `Registry::register_attribute` while also providing a replacement.
---
`register_attr` is a direct replacement for `#![feature(custom_attribute)]` (https://github.com/rust-lang/rust/issues/29642), except it doesn't rely on implicit fallback from unresolved attributes to custom attributes (which was always hacky and is the primary reason for the removal of `custom_attribute`) and requires registering the attribute explicitly.
It's not clear whether it should go through stabilization or not.
It's quite possible that all the uses should migrate to `#![register_tool]` (https://github.com/rust-lang/rust/issues/66079) instead.
---
Details:
- The naming is `register_attr`/`register_tool` rather than some `register_attributes` (plural, no abbreviation) for consistency with already existing attributes like `cfg_attr`, or `feature`, etc.
---
Previous attempt: https://github.com/rust-lang/rust/pull/57921
cc https://github.com/rust-lang/rust/issues/44690
Tracking issues: #66079 (`register_tool`), #66080 (`register_attr`)
Closes https://github.com/rust-lang/rust/issues/29642
Split libsyntax apart
In this PR the general idea is to separate the AST, parser, and friends by a more data / logic structure (tho not fully realized!) by separating out the parser and macro expansion code from libsyntax. Specifically have now three crates instead of one (libsyntax):
- libsyntax:
- concrete syntax tree (`syntax::ast`)
- definition of tokens and token-streams (`syntax::{token, tokenstream}`) -- used by `syntax::ast`
- visitors (`syntax::visit`, `syntax::mut_visit`)
- shared definitions between `libsyntax_expand`
- feature gating (`syntax::feature_gate`) -- we could possibly move this out to its own crater later.
- attribute and meta item utilities, including used-marking (`syntax::attr`)
- pretty printer (`syntax::print`) -- this should possibly be moved out later. For now I've reduced down the dependencies to a single essential one which could be broken via `ParseSess`. This entails that e.g. `Debug` impls for `Path` cannot reference the pretty printer.
- definition of `ParseSess` (`syntax::sess`) -- this is used by `syntax::{attr, print, feature_gate}` and is a common definition used by the parser and other things like librustc.
- the `syntax::source_map` -- this includes definitions used by `syntax::ast` and other things but could ostensibly be moved `syntax_pos` since that is more related to this module.
- a smattering of misc utilities not sufficiently important to itemize -- some of these could be moved to where they are used (often a single place) but I wanted to limit the scope of this PR.
- librustc_parse:
- parser (`rustc_parse::parser`) -- reading a file and such are defined in the crate root tho.
- lexer (`rustc_parse::lexer`)
- validation of meta grammar (post-expansion) in (`rustc_parse::validate_attr`)
- libsyntax_expand -- this defines the infra for macro expansion and conditional compilation but this is not libsyntax_ext; we might want to merge them later but currently libsyntax_expand is depended on by librustc_metadata which libsyntax_ext is not.
- conditional compilation (`syntax_expand::config`) -- moved from `syntax::config` to here
- the bulk of this crate is made up of the old `syntax::ext`
r? @estebank
rustc_metadata: don't let LLVM confuse rmeta blobs for COFF object files.
This has likely been a silent issue since 1.10 but only caused trouble recently (see https://github.com/rust-lang/rust/issues/65536#issuecomment-552018224), when recent changes to the `rmeta` schema introduced more opportunities for COFF parse errors.
To prevent any undesired interactions with old compilers, I've renamed the file inside `rlib`s from `rust.metadata.bin` to `lib.rmeta` (not strongly attached to it, suggestions welcome).
Fixes#65536.
<hr/>
Before:
```
$ llvm-objdump -all-headers build/*/stage1-std/*/release/deps/libcore-*.rmeta
build/x86_64-unknown-linux-gnu/stage1-std/x86_64-unknown-linux-gnu/release/deps/libcore-6b9e8b5a59b79a1d.rmeta: file format COFF-<unknown arch>
architecture: unknown
start address: 0x00000000
Sections:
Idx Name Size VMA Type
SYMBOL TABLE:
```
After:
```
$ llvm-objdump -all-headers build/*/stage1-std/*/release/deps/libcore-*.rmeta
llvm-objdump: error: 'build/x86_64-unknown-linux-gnu/stage1-std/x86_64-unknown-linux-gnu/release/deps/libcore-6b9e8b5a59b79a1d.rmeta':
The file was not recognized as a valid object file
```
[mir-opt] Handle return place in ConstProp and improve SimplifyLocals pass
Temporarily rebased on top of #66074. The top 2 commits are new.
r? @oli-obk
[mir-opt] Implement pass to remove branches on uninhabited variants
Based on discussion [here](https://github.com/rust-lang/rust/pull/64890#discussion_r333612125), this is a pass to eliminate dead code that is caused by branching on an enum with uninhabited variants.
r? @oli-obk
Rollup of 6 pull requests
Successful merges:
- #65949 (Move promotion into its own pass)
- #65994 (Point at where clauses where the associated item was restricted)
- #66050 (Fix C aggregate-passing ABI on powerpc)
- #66134 (Point at formatting descriptor string when it is invalid)
- #66172 (Stabilize @file command line arguments)
- #66226 (add link to unstable book for asm! macro)
Failed merges:
r? @ghost
Point at formatting descriptor string when it is invalid
When a formatting string contains an invalid descriptor, point at it
instead of the argument:
```
error: unknown format trait `foo`
--> $DIR/ifmt-bad-arg.rs:86:17
|
LL | println!("{:foo}", 1);
| ^^^
|
= note: the only appropriate formatting traits are:
- ``, which uses the `Display` trait
- `?`, which uses the `Debug` trait
- `e`, which uses the `LowerExp` trait
- `E`, which uses the `UpperExp` trait
- `o`, which uses the `Octal` trait
- `p`, which uses the `Pointer` trait
- `b`, which uses the `Binary` trait
- `x`, which uses the `LowerHex` trait
- `X`, which uses the `UpperHex` trait
```
We bailed out of `QualifyAndPromoteConsts` immediately if the
`min_const_fn` checks failed, which sometimes resulted in additional,
spurious errors since promotion was skipped.
We now do promotion in a completely separate pass, so this is no longer
an issue.
Remove promotion candidate gathering and checking from `qualify_consts.rs`
This makes promotion candidate gathering and checking the exclusive domain of `promote_consts`, but the `QualifyAndPromoteConsts` pass is still responsible for both const-checking and creating promoted MIR fragments.
This should not be merged until the beta branches on Nov. 5.
r? @eddyb
consistent handling of missing sysroot spans
Due to https://github.com/rust-lang/rust/issues/53081, sysroot spans (pointing to code in libcore/libstd/...) fails to print on some x86 runners. This consolidates the ignore directives for that and references the relevant issue.
I also did that for the generated derive-error-span tests -- but there the script and the tests were not entirely in sync any more since https://github.com/rust-lang/rust/pull/64151. Cc @estebank @varkor
Stabilize --extern flag without a path.
This stabilizes the `--extern` flag without a path, implemented in #54116.
This flag is used to add a crate that may be found in the search path to the extern prelude. The intent of stabilizing this now is to change Cargo to emit this flag for `proc_macro` when building a proc-macro crate. This will allow the ability to elide `extern crate proc_macro;` for proc-macros, one of the few places where it is still necessary.
It is intended that Cargo may also use this flag for other cases in the future as part of the [std-aware work](https://github.com/rust-lang/wg-cargo-std-aware/). There will likely be some kind of syntax where users may declare dependencies on other crates (such as `alloc`), and Cargo will use this flag so that they may be used like any other crate. At this time there are no short-term plans to use it for anything other than proc-macro.
This will not help for non-proc-macro crates that use `proc_macro`, which I believe is not too common?
An alternate approach for proc-macro is to use the `meta` crate, but from my inquiries there doesn't appear to be anyone interested in pushing that forward. The `meta` crate also doesn't help with things like `alloc` or `test`.
cc #57288
invalid_value lint: fix help text
Now that we also warn about `MaybUninit::uninit().assume_init()`, just telling people "use `MaybeUninit`" isn't always sufficient. And anyway this seems like an important enough point to mention it here.
Have tidy ensure that we document all `unsafe` blocks in libcore
cc @rust-lang/libs
I documented a few and added ignore flags on the other files. We can incrementally document the files, but won't regress any files this way.
Add future incompatibility lint for `array.into_iter()`
This is for #65819. This lint warns when calling `into_iter` on an array directly. That's because today the method call resolves to `<&[T] as IntoIterator>::into_iter` but that would change when adding `IntoIterator` impls for arrays. This problem is discussed in detail in #65819.
We still haven't decided how to proceed exactly, but it seems like adding a lint is a good idea regardless?
Also: this is the first time I implement a lint, so there are probably a lot of things I can improve. I used a different strategy than @scottmcm describes [here](https://github.com/rust-lang/rust/pull/65819#issuecomment-548667847) since I already started implementing this before they commented.
### TODO
- [x] Decide if we want this lint -> apparently [we want](https://github.com/rust-lang/rust/pull/65819#issuecomment-548964818)
- [x] Open a lint-tracking-issue and add the correct issue number in the code -> https://github.com/rust-lang/rust/issues/66145
A scheme for more macro-matcher friendly pre-expansion gating
Pre-expansion gating will now avoid gating macro matchers that did not result in `Success(...)`. That is, the following is now OK despite `box 42` being a valid `expr` and that form being pre-expansion gated:
```rust
macro_rules! m {
($e:expr) => { 0 }; // This fails on the input below due to `, foo`.
(box $e:expr, foo) => { 1 }; // Successful matcher, we should get `2`.
}
fn main() {
assert_eq!(1, m!(box 42, foo));
}
```
Closes https://github.com/rust-lang/rust/issues/65846.
r? @petrochenkov
cc @Mark-Simulacrum
syntax: ABI-oblivious grammar
This PR has the following effects:
1. `extern $lit` is now legal where `$lit:literal` and `$lit` is substituted for a string literal.
2. `extern "abi_that_does_not_exist"` is now *syntactically* legal whereas before, the set of ABI strings was hard-coded into the grammar of the language. With this PR, the set of ABIs are instead validated and translated during lowering. That seems more appropriate.
3. `ast::FloatTy` is now distinct from `rustc_target::abi::FloatTy`. The former is used substantially more and the translation between them is only necessary in a single place.
4. As a result of 2-3, libsyntax no longer depends on librustc_target, which should improve pipe-lining somewhat.
cc @rust-lang/lang -- the points 1-2 slightly change the definition of the language but in a way which seems consistent with our general principles (in particular wrt. the discussions of turning things into semantic errors). I expect this to be uncontroversial but it's worth letting y'all know. :)
r? @varkor
Use structured suggestions for missing associated items
When encountering an `impl` that is missing associated items required by its `trait`, use structured suggestions at an appropriate place in the `impl`.
