Auto merge of #11698 - a1phyr:waker_clone_and_wake, r=y21

Add `waker_clone_and_wake` lint to check needless `Waker` clones

Check for patterns of `waker.clone().wake()` and replace them with `waker.wake_by_ref()`.

An alternative name could be `waker_clone_then_wake`

changelog: [ `waker_clone_wake`]: new lint
This commit is contained in:
bors 2023-10-26 21:01:40 +00:00
commit 2f0f4ddcf7
8 changed files with 137 additions and 0 deletions

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@ -5589,6 +5589,7 @@ Released 2018-09-13
[`verbose_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#verbose_bit_mask
[`verbose_file_reads`]: https://rust-lang.github.io/rust-clippy/master/index.html#verbose_file_reads
[`vtable_address_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#vtable_address_comparisons
[`waker_clone_wake`]: https://rust-lang.github.io/rust-clippy/master/index.html#waker_clone_wake
[`while_immutable_condition`]: https://rust-lang.github.io/rust-clippy/master/index.html#while_immutable_condition
[`while_let_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#while_let_loop
[`while_let_on_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#while_let_on_iterator

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@ -443,6 +443,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::methods::USELESS_ASREF_INFO,
crate::methods::VEC_RESIZE_TO_ZERO_INFO,
crate::methods::VERBOSE_FILE_READS_INFO,
crate::methods::WAKER_CLONE_WAKE_INFO,
crate::methods::WRONG_SELF_CONVENTION_INFO,
crate::methods::ZST_OFFSET_INFO,
crate::min_ident_chars::MIN_IDENT_CHARS_INFO,

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@ -112,6 +112,7 @@ mod useless_asref;
mod utils;
mod vec_resize_to_zero;
mod verbose_file_reads;
mod waker_clone_wake;
mod wrong_self_convention;
mod zst_offset;
@ -3632,6 +3633,28 @@ declare_clippy_lint! {
"`as_str` used to call a method on `str` that is also available on `String`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `waker.clone().wake()`
///
/// ### Why is this bad?
/// Cloning the waker is not necessary, `wake_by_ref()` enables the same operation
/// without extra cloning/dropping.
///
/// ### Example
/// ```rust,ignore
/// waker.clone().wake();
/// ```
/// Should be written
/// ```rust,ignore
/// waker.wake_by_ref();
/// ```
#[clippy::version = "1.75.0"]
pub WAKER_CLONE_WAKE,
perf,
"cloning a `Waker` only to wake it"
}
pub struct Methods {
avoid_breaking_exported_api: bool,
msrv: Msrv,
@ -3777,6 +3800,7 @@ impl_lint_pass!(Methods => [
ITER_OUT_OF_BOUNDS,
PATH_ENDS_WITH_EXT,
REDUNDANT_AS_STR,
WAKER_CLONE_WAKE,
]);
/// Extracts a method call name, args, and `Span` of the method name.
@ -4365,6 +4389,9 @@ impl Methods {
}
unnecessary_literal_unwrap::check(cx, expr, recv, name, args);
},
("wake", []) => {
waker_clone_wake::check(cx, expr, recv);
}
("write", []) => {
readonly_write_lock::check(cx, expr, recv);
}

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@ -0,0 +1,32 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{is_trait_method, match_def_path, paths};
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_span::sym;
use super::WAKER_CLONE_WAKE;
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>) {
let ty = cx.typeck_results().expr_ty(recv);
if let Some(did) = ty.ty_adt_def()
&& match_def_path(cx, did.did(), &paths::WAKER)
&& let ExprKind::MethodCall(_, waker_ref, &[], _) = recv.kind
&& is_trait_method(cx, recv, sym::Clone)
{
let mut applicability = Applicability::MachineApplicable;
let snippet = snippet_with_applicability(cx, waker_ref.span.source_callsite(), "..", &mut applicability);
span_lint_and_sugg(
cx,
WAKER_CLONE_WAKE,
expr.span,
"cloning a `Waker` only to wake it",
"replace with",
format!("{snippet}.wake_by_ref()"),
applicability,
);
}
}

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@ -112,6 +112,7 @@ pub const VEC_RESIZE: [&str; 4] = ["alloc", "vec", "Vec", "resize"];
pub const INSTANT_NOW: [&str; 4] = ["std", "time", "Instant", "now"];
pub const VEC_IS_EMPTY: [&str; 4] = ["alloc", "vec", "Vec", "is_empty"];
pub const VEC_POP: [&str; 4] = ["alloc", "vec", "Vec", "pop"];
pub const WAKER: [&str; 4] = ["core", "task", "wake", "Waker"];
pub const OPTION_UNWRAP: [&str; 4] = ["core", "option", "Option", "unwrap"];
pub const OPTION_EXPECT: [&str; 4] = ["core", "option", "Option", "expect"];
#[expect(clippy::invalid_paths)] // not sure why it thinks this, it works so

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@ -0,0 +1,29 @@
#[derive(Clone)]
pub struct Custom;
impl Custom {
pub fn wake(self) {}
}
macro_rules! mac {
($cx:ident) => {
$cx.waker()
};
}
pub fn wake(cx: &mut std::task::Context) {
cx.waker().wake_by_ref();
mac!(cx).wake_by_ref();
}
pub fn no_lint(cx: &mut std::task::Context, c: &Custom) {
c.clone().wake();
let w = cx.waker().clone();
w.wake();
cx.waker().clone().wake_by_ref();
}
fn main() {}

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@ -0,0 +1,29 @@
#[derive(Clone)]
pub struct Custom;
impl Custom {
pub fn wake(self) {}
}
macro_rules! mac {
($cx:ident) => {
$cx.waker()
};
}
pub fn wake(cx: &mut std::task::Context) {
cx.waker().clone().wake();
mac!(cx).clone().wake();
}
pub fn no_lint(cx: &mut std::task::Context, c: &Custom) {
c.clone().wake();
let w = cx.waker().clone();
w.wake();
cx.waker().clone().wake_by_ref();
}
fn main() {}

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@ -0,0 +1,17 @@
error: cloning a `Waker` only to wake it
--> $DIR/waker_clone_wake.rs:15:5
|
LL | cx.waker().clone().wake();
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `cx.waker().wake_by_ref()`
|
= note: `-D clippy::waker-clone-wake` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::waker_clone_wake)]`
error: cloning a `Waker` only to wake it
--> $DIR/waker_clone_wake.rs:17:5
|
LL | mac!(cx).clone().wake();
| ^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `mac!(cx).wake_by_ref()`
error: aborting due to 2 previous errors