New lint: `unused_async`
changelog: Adds a lint, `unused_async`, which checks for async functions with no await statements
`unused_async` is a lint that reduces code smell and overhead by encouraging async functions to be refactored into synchronous functions.
Fixes#7176
### Examples
```rust
async fn get_random_number() -> i64 {
4 // Chosen by fair dice roll. Guaranteed to be random.
}
```
Could be written as:
```rust
fn get_random_number() -> i64 {
4 // Chosen by fair dice roll. Guaranteed to be random.
}
```
Something like this, however, should **not** be caught by clippy:
```rust
#[async_trait]
trait AsyncTrait {
async fn foo();
}
struct Bar;
#[async_trait]
impl AsyncTrait for Bar {
async fn foo() {
println!("bar");
}
}
```
Stop linting `else if let` pattern in [`option_if_let_else`] lint
For readability concerns, it is counterproductive to lint `else if let` pattern.
Unfortunately the suggested code is much less readable.
Fixes: #7006
changelog: stop linting `else if let` pattern in [`option_if_let_else`] lint
Remove CrateNum parameter for queries that only work on local crate
The pervasive `CrateNum` parameter is a remnant of the multi-crate rustc idea.
Using `()` as query key in those cases avoids having to worry about the validity of the query key.
Remove CrateNum parameter for queries that only work on local crate
The pervasive `CrateNum` parameter is a remnant of the multi-crate rustc idea.
Using `()` as query key in those cases avoids having to worry about the validity of the query key.
rustc_codegen_ssa: only create backend `BasicBlock`s as-needed.
Instead of creating one backend (e.g. LLVM) block per MIR block ahead of time, and then deleting the ones that weren't visited, this PR moves to creating the blocks as they're needed (either reached via the RPO visit, or used as the target of a branch from a different block).
As deleting a block was the only `unsafe` builder method (generally we only *create* backend objects, not *remove* them), that's gone now and codegen is overall a bit safer.
The only change in output is the order of LLVM blocks (which AFAIK has no semantic meaning, other than the first block being the entry block). This happens because the blocks are now created due to control-flow edges, rather than MIR block order.
I'm making this a standalone PR because I keep getting wild perf results when I change *anything* in codegen, but if you want to read more about my plans in this area, see https://github.com/rust-lang/rust/pull/84771#issuecomment-830636256 (and https://github.com/rust-lang/rust/pull/84771#issue-628295651 - but that may be a bit outdated).
(You may notice some of the APIs in this PR, like `append_block`, don't help with the future plans - but I didn't want to include the necessary refactors that pass a build around everywhere, in this PR, so it's a small compromise)
r? `@nagisa` `@bjorn3`
Metadata collection monster searching for Clippy's configuration options
This PR teaches our lovely metadata collection monster which configurations are available inside Clippy. It then adds a new *Configuration* section to the lint documentation.
---
The implementation uses the `define_Conf!` macro to create a vector of metadata during compilation. This enables easy collection and parsing without the need of searching for the struct during a lint-pass (and it's quite elegant IMO). The information is then parsed into an intermediate struct called `ClippyConfiguration` which will be saved inside the `MetadataCollector` struct itself. It is currently only used to generate the *Configuration* section in the lint documentation, but I'm thinking about adding an overview of available configurations to the website. Saving them in this intermediate state without formatting them right away enables this in the future.
The new parsing will also allow us to have a documentation that spans over multiple lines in the future. For example, this will be valid when the old script has been removed:
```rust
/// Lint: BLACKLISTED_NAME.
/// The list of blacklisted names to lint about. NB: `bar` is not here since it has legitimate uses
(blacklisted_names: Vec<String> = ["foo", "baz", "quux"].iter().map(ToString::to_string).collect())
```
The deprecation reason is also currently being collected but not used any further and that's basically it.
---
See: #7172 for the full metadata collection to-do list or to suggest a new feature in connection to it 🙃
---
changelog: none
r? `@flip1995`
cc `@camsteffen` It would be great if you could also review this PR as you have recently worked on Clippy's `define_Conf!` macro.
Fix unused attributes on macro_rules.
The `unused_attributes` lint wasn't firing on attributes of `macro_rules` definitions. The consequence is that many attributes are silently ignored on `macro_rules`. The reason is that `unused_attributes` is a late-lint pass, and only has access to the HIR, which does not have macro_rules definitions.
My solution here is to change `non_exported_macro_attrs` to be `macro_attrs` (a list of all attributes used for `macro_rules`, instead of just those for `macro_export`), and then to check this list in the `unused_attributes` lint. There are a number of alternate approaches, but this seemed the most reliable and least invasive. I am open to completely different approaches, though.
One concern is that I don't fully understand the implications of extending `non_exported_macro_attrs` to include non-exported macros. That list was originally added in #62042 to handle stability attributes, so I suspect it was just an optimization since that was all that was needed. It was later extended to be included in SVH in #83901. #80641 also added a use to check for `invalid` attributes, which seems a little odd to me (it didn't validate non-exported macros, and seems highly specific).
Overall, there doesn't seem to be a clear story of when `unused_attributes` should be used versus an error like E0518. I considered alternatively using an "allow list" of built-in attributes that can be used on macro_rules (allow, warn, deny, forbid, cfg, cfg_attr, macro_export, deprecated, doc), but I feel like that could be a pain to maintain.
Some built-in attributes already present hard-errors when used with macro_rules. These are each hard-coded in various places:
- `derive`
- `test` and `bench`
- `proc_macro` and `proc_macro_derive`
- `inline`
- `global_allocator`
The primary motivation is that I sometimes see people use `#[macro_use]` in front of `macro_rules`, which indicates there is some confusion out there (evident that there was even a case of it in rustc).
Remove support for floating-point constants in asm!
Floating-point constants aren't very useful anyways and this simplifies
the code since the type check can now be done in typeck.
cc `@rust-lang/wg-inline-asm`
r? `@nagisa`
Add `cargo collect-metadata` as an cargo alias for the metadata collection lint
This PR adds a new alias to run the metadata collection monster on `clippy_lints`. I'm currently using it to create the `metadata_collection.json` file and I plan to use it in the `deply.sh` script. Having it as a new alias enables us to simply use:
```sh
cargo collect-metadata
```
It sometimes requires running `cargo clean` before collecting the metadata due to caching. I'm still debating if I should include a cargo clean as part of the `run_metadata_collection_lint` test or not. Input on this would be greatly appreciated 🙃
That's it, just a small change that can be reviewed and merged in parallel to #7214.
---
See: #7172 for the full metadata collection to-do list or to suggest a new feature in connection to it.
---
changelog: none
r? `@flip1995` btw. feel free to pass these PRs one to other team members as well if you want.
Reachable statics have reachable initializers
Static initializer can read other statics. Initializers are evaluated at
compile time, and so their content could become inlined into another
crate. Ensure that initializers of reachable statics are also reachable.
Previously, when an item incorrectly considered to be unreachable was
reached from another crate an attempt would be made to codegen it. The
attempt could fail with an ICE (in the case MIR wasn't available to do
so) in some circumstances the attempt could also succeed resulting in
a local codegen of non-local items, including static ones.
Fixes#84455.
rustc_codegen_ssa: generate MSVC cleanup pads on demand, like GNU landing pads.
This unblocks #84993 in terms of codegen tests, as it brings the MSVC-style (`cleanup_pad`) EH (LLVM) block order in line with the GNU-style (`landing_pad`) EH (LLVM) block order, by having both of them be on-demand (instead of MSVC-style being eager and GNU-style lazy/on-demand).
It also unifies the two implementations a bit, similar to #84699, but in the opposite direction (as that attempt made both kinds of EH pads eagerly built).
~~Opening as draft because I haven't done enough Windows testing just yet, of both this PR, and of #84993 rebased on it.~~ (**EDIT**: seems to be working as expected)
r? `@nagisa`
CTFE validation: handle pointers in str
I also finally learned how I can match *some* NOTEs in a ui test without matching all of them, and applied that to some const tests in the 2nd commit where I added NOTE because I did not know what I was doing. I can separate this into its own PR if you prefer.
Fixes https://github.com/rust-lang/rust/issues/83182
r? `@oli-obk`
Check for inline assembly in THIR unsafeck
#83129 was merged recently and added a THIR unsafe checker. This adds a check for inline assembly. (and this is 2x simpler than the MIR version, which has to check for `asm` and `llvm_asm` in two separate spots!)
see also rust-lang/project-thir-unsafeck#7
Do not allocate or unwind after fork
### Objective scenarios
* Make (simple) panics safe in `Command::pre_exec_hook`, including most `panic!` calls, `Option::unwrap`, and array bounds check failures.
* Make it possible to `libc::fork` and then safely panic in the child (needed for the above, but this requirement means exposing the new raw hook API which the `Command` implementation needs).
* In singlethreaded programs, where panic in `pre_exec_hook` is already memory-safe, prevent the double-unwinding malfunction #79740.
I think we want to make panic after fork safe even though the post-fork child environment is only experienced by users of `unsafe`, beause the subset of Rust in which any panic is UB is really far too hazardous and unnatural.
#### Approach
* Provide a way for a program to, at runtime, switch to having panics abort. This makes it possible to panic without making *any* heap allocations, which is needed because on some platforms malloc is UB in a child forked from a multithreaded program (see https://github.com/rust-lang/rust/pull/80263#issuecomment-774272370, and maybe also the SuS [spec](https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html)).
* Make that change in the child spawned by `Command`.
* Document the rules comprehensively enough that a programmer has a fighting chance of writing correct code.
* Test that this all works as expected (and in particular, that there aren't any heap allocations we missed)
Fixes#79740
#### Rejected (or previously attempted) approaches
* Change the panic machinery to be able to unwind without allocating, at least when the payload and message are both `'static`. This seems like it would be even more subtle. Also that is a potentially-hot path which I don't want to mess with.
* Change the existing panic hook mechanism to not convert the message to a `String` before calling the hook. This would be a surprising change for existing code and would not be detected by the type system.
* Provide a `raw_panic_hook` function to intercept panics in a way that doesn't allocate. (That was an earlier version of this MR.)
### History
This MR could be considered a v2 of #80263. Thanks to everyone who commented there. In particular, thanks to `@m-ou-se,` `@Mark-Simulacrum` and `@hyd-dev.` (Tagging you since I think you might be interested in this new MR.) Compared to #80263, this MR has very substantial changes and additions.
Additionally, I have recently (2021-04-20) completely revised this series following very helpful comments from `@m-ou-se.`
r? `@m-ou-se`
Remove some unncessary spaces from pretty-printed tokenstream output
In addition to making the output look nicer for all crates, this also
aligns the pretty-printing output with what the `rental` crate expects.
This will allow us to eventually disable a backwards-compat hack in a
follow-up PR.
See https://github.com/rust-lang/rust/issues/84428 for some background information about why we want to make this change. Note that this change would be desirable (but not particularly necessary) even if `rental` didn't exist, so we're not adding any crate-specific hacks into the compiler.
