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.
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.
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.
`needless_collect` enhancements
fixes#7164
changelog: `needless_collect`: For `BTreeMap` and `HashMap` lint only `is_empty`, as `len` might produce different results than iter's `count`
changelog: `needless_collect`: Lint `LinkedList` and `BinaryHeap` in direct usage case as well
Trigger [`wrong_self_convention`] only if it has implicit self
Lint [`wrong_self_convention`] only if the impl or trait has `self` _per sé_.
Fixes: #7179
changelog: trigger [`wrong_self_convention`] only if it has implicit self
match_single_binding: Fix invalid suggestion when match scrutinee has side effects
fixes#7094
changelog: `match_single_binding`: Fix invalid suggestion when match scrutinee has side effects
---
`Expr::can_have_side_effects` is used to determine the scrutinee has side effects, while this method is a little bit conservative for our use case. But I'd like to use it to avoid reimplementation of the method and too much heuristics. If you think this is problematic, then I'll implement a custom visitor to address it.
`while_let_on_iterator` Improvements
fixes: #6491fixes: #6231fixes: #5844fixes: #1924fixes: #1033
The check for whether a field can be borrowed should probably be moved to utils at some point, but it would require some cleanup work and knowing what parts can actually be shared.
changelog: Suggest `&mut iter` when the iterator is used after the loop.
changelog: Suggest `&mut iter` when the iterator is a field in a struct.
changelog: Don't lint when the iterator is a field in a struct, and the struct is used in the loop.
changelog: Lint when the loop is nested in another loop, but suggest `&mut iter` unless the iterator is from a local declared inside the loop.
* Suggest `&mut iter` when the iterator is used after the loop.
* Suggest `&mut iter` when the iterator is a field in a struct.
* Don't lint when the iterator is a field in a struct, and the struct is
used in the loop.
* Lint when the loop is nested in another loop, but suggest `&mut iter`
unless the iterator is from a local declared inside the loop.
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
Metadata collection monster eating deprecated lints
This adds the collection of deprecated lints to the metadata collection monster. The JSON output has the same structure with the *new* lint group "DEPRECATED". Here is one of fourteen examples it was able to dig up in Clippy's code:
```JSON
{
"id": "assign_op_pattern",
"id_span": {
"path": "src/assign_ops.rs",
"line": 34
},
"group": "clippy::style",
"docs": " **What it does:** Checks for `a = a op b` or `a = b commutative_op a` patterns.\n\n **Why is this bad?** These can be written as the shorter `a op= b`.\n\n **Known problems:** While forbidden by the spec, `OpAssign` traits may have\n implementations that differ from the regular `Op` impl.\n\n **Example:**\n ```rust\n let mut a = 5;\n let b = 0;\n // ...\n // Bad\n a = a + b;\n\n // Good\n a += b;\n ```\n",
"applicability": {
"is_multi_part_suggestion": false,
"applicability": "MachineApplicable"
}
}
```
And you! Yes you! Sir or Madam can get all of this **for free** in Clippy if this PR gets merged. (Sorry for the silliness ^^)
---
See: #7172 for the full metadata collection to-do list or to suggest a new feature in connection to it 🙃
---
changelog: none
r? `@flip1995`
This PR implements span quoting, allowing proc-macros to produce spans
pointing *into their own crate*. This is used by the unstable
`proc_macro::quote!` macro, allowing us to get error messages like this:
```
error[E0412]: cannot find type `MissingType` in this scope
--> $DIR/auxiliary/span-from-proc-macro.rs:37:20
|
LL | pub fn error_from_attribute(_args: TokenStream, _input: TokenStream) -> TokenStream {
| ----------------------------------------------------------------------------------- in this expansion of procedural macro `#[error_from_attribute]`
...
LL | field: MissingType
| ^^^^^^^^^^^ not found in this scope
|
::: $DIR/span-from-proc-macro.rs:8:1
|
LL | #[error_from_attribute]
| ----------------------- in this macro invocation
```
Here, `MissingType` occurs inside the implementation of the proc-macro
`#[error_from_attribute]`. Previosuly, this would always result in a
span pointing at `#[error_from_attribute]`
This will make many proc-macro-related error message much more useful -
when a proc-macro generates code containing an error, users will get an
error message pointing directly at that code (within the macro
definition), instead of always getting a span pointing at the macro
invocation site.
This is implemented as follows:
* When a proc-macro crate is being *compiled*, it causes the `quote!`
macro to get run. This saves all of the sapns in the input to `quote!`
into the metadata of *the proc-macro-crate* (which we are currently
compiling). The `quote!` macro then expands to a call to
`proc_macro::Span::recover_proc_macro_span(id)`, where `id` is an
opaque identifier for the span in the crate metadata.
* When the same proc-macro crate is *run* (e.g. it is loaded from disk
and invoked by some consumer crate), the call to
`proc_macro::Span::recover_proc_macro_span` causes us to load the span
from the proc-macro crate's metadata. The proc-macro then produces a
`TokenStream` containing a `Span` pointing into the proc-macro crate
itself.
The recursive nature of 'quote!' can be difficult to understand at
first. The file `src/test/ui/proc-macro/quote-debug.stdout` shows
the output of the `quote!` macro, which should make this eaier to
understand.
This PR also supports custom quoting spans in custom quote macros (e.g.
the `quote` crate). All span quoting goes through the
`proc_macro::quote_span` method, which can be called by a custom quote
macro to perform span quoting. An example of this usage is provided in
`src/test/ui/proc-macro/auxiliary/custom-quote.rs`
Custom quoting currently has a few limitations:
In order to quote a span, we need to generate a call to
`proc_macro::Span::recover_proc_macro_span`. However, proc-macros
support renaming the `proc_macro` crate, so we can't simply hardcode
this path. Previously, the `quote_span` method used the path
`crate::Span` - however, this only works when it is called by the
builtin `quote!` macro in the same crate. To support being called from
arbitrary crates, we need access to the name of the `proc_macro` crate
to generate a path. This PR adds an additional argument to `quote_span`
to specify the name of the `proc_macro` crate. Howver, this feels kind
of hacky, and we may want to change this before stabilizing anything
quote-related.
Additionally, using `quote_span` currently requires enabling the
`proc_macro_internals` feature. The builtin `quote!` macro
has an `#[allow_internal_unstable]` attribute, but this won't work for
custom quote implementations. This will likely require some additional
tricks to apply `allow_internal_unstable` to the span of
`proc_macro::Span::recover_proc_macro_span`.
Move `inconsistent_struct_constructor` to pedantic
The whole point of named fields is that we don't have to worry about
order. The names, not the position, communicate the information, so
worrying about consistency for consistency's sake is pedantic to a *T*.
Cf. #7192.
changelog: [`inconsistent_struct_constructor`] is moved to pedantic.
wchargin-branch: inconsistent-struct-constructor-pedantic
Fix stack overflow issue in `redundant_pattern_matching`
Fixes#7169
~~cc `@Jarcho` Since tomorrow is release day and we need to get this also fixed in beta, I'll just revert the PR instead of looking into the root issue. Your changes are good, so if you have an idea what could cause this stack overflow and know how to fix it, please open a PR that reverts this revert with a fix.~~
r? `@llogiq`
changelog: none (fixes stack overflow, but this was introduced in this release cycle)
The whole point of named fields is that we don't have to worry about
order. The names, not the position, communicate the information, so
worrying about consistency for consistency's sake is pedantic to a *T*.
Fixes#7192.
wchargin-branch: inconsistent-struct-constructor-pedantic
wchargin-source: 4fe078a21c77ceb625e58fa3b90b613fc4fa6a76
Fix needless_quesiton_mark false positive
changelog: Fix [`needless_question_mark`] false positive where the inner value is implicity dereferenced by the question mark.
Fixes#7107
