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Auto merge of #9697 - Alexendoo:let-underscore-uplift, r=flip1995
Mark `let_underscore_lock` and `let_underscore_drop` as uplifted Here I've renamed both the uplifted lints, however rustc's `let_underscore_lock` is slightly less capable than the clippy lint as it doesn't catch `parking_lot` types or `Result<Guard, ..>`, should we still remove it? The `Result` change looks like it was unintentional to me so that could probably be fixed upstream changelog: Uplift [`let_underscore_drop`] to rustc rust-lang/rust#97739 changelog: Remove overlap between rustc's `let_underscore_lock` and Clippy's [`let_underscore_lock`] r? `@flip1995`
2 parents 8e03f91 + 9306540 commit 3f4287c

18 files changed

+145
-329
lines changed

‎clippy_lints/src/let_underscore.rs‎

Lines changed: 41 additions & 103 deletions
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,11 @@
11
use clippy_utils::diagnostics::span_lint_and_help;
2-
use clippy_utils::ty::{is_must_use_ty, is_type_diagnostic_item, match_type};
2+
use clippy_utils::ty::{is_must_use_ty, match_type};
33
use clippy_utils::{is_must_use_func_call, paths};
4-
use if_chain::if_chain;
54
use rustc_hir::{Local, PatKind};
65
use rustc_lint::{LateContext, LateLintPass};
76
use rustc_middle::lint::in_external_macro;
87
use rustc_middle::ty::subst::GenericArgKind;
98
use rustc_session::{declare_lint_pass, declare_tool_lint};
10-
use rustc_span::{sym, Symbol};
119

1210
declare_clippy_lint! {
1311
/// ### What it does
@@ -35,8 +33,9 @@ declare_clippy_lint! {
3533

3634
declare_clippy_lint! {
3735
/// ### What it does
38-
/// Checks for `let _ = sync_lock`.
39-
/// This supports `mutex` and `rwlock` in `std::sync` and `parking_lot`.
36+
/// Checks for `let _ = sync_lock`. This supports `mutex` and `rwlock` in
37+
/// `parking_lot`. For `std` locks see the `rustc` lint
38+
/// [`let_underscore_lock`](https://doc.rust-lang.org/nightly/rustc/lints/listing/deny-by-default.html#let-underscore-lock)
4039
///
4140
/// ### Why is this bad?
4241
/// This statement immediately drops the lock instead of
@@ -60,47 +59,7 @@ declare_clippy_lint! {
6059
"non-binding let on a synchronization lock"
6160
}
6261

63-
declare_clippy_lint! {
64-
/// ### What it does
65-
/// Checks for `let _ = <expr>`
66-
/// where expr has a type that implements `Drop`
67-
///
68-
/// ### Why is this bad?
69-
/// This statement immediately drops the initializer
70-
/// expression instead of extending its lifetime to the end of the scope, which
71-
/// is often not intended. To extend the expression's lifetime to the end of the
72-
/// scope, use an underscore-prefixed name instead (i.e. _var). If you want to
73-
/// explicitly drop the expression, `std::mem::drop` conveys your intention
74-
/// better and is less error-prone.
75-
///
76-
/// ### Example
77-
/// ```rust
78-
/// # struct DroppableItem;
79-
/// {
80-
/// let _ = DroppableItem;
81-
/// // ^ dropped here
82-
/// /* more code */
83-
/// }
84-
/// ```
85-
///
86-
/// Use instead:
87-
/// ```rust
88-
/// # struct DroppableItem;
89-
/// {
90-
/// let _droppable = DroppableItem;
91-
/// /* more code */
92-
/// // dropped at end of scope
93-
/// }
94-
/// ```
95-
#[clippy::version = "1.50.0"]
96-
pub LET_UNDERSCORE_DROP,
97-
pedantic,
98-
"non-binding let on a type that implements `Drop`"
99-
}
100-
101-
declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE, LET_UNDERSCORE_LOCK, LET_UNDERSCORE_DROP]);
102-
103-
const SYNC_GUARD_SYMS: [Symbol; 3] = [sym::MutexGuard, sym::RwLockReadGuard, sym::RwLockWriteGuard];
62+
declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE, LET_UNDERSCORE_LOCK]);
10463

10564
const SYNC_GUARD_PATHS: [&[&str]; 3] = [
10665
&paths::PARKING_LOT_MUTEX_GUARD,
@@ -110,64 +69,43 @@ const SYNC_GUARD_PATHS: [&[&str]; 3] = [
11069

11170
impl<'tcx> LateLintPass<'tcx> for LetUnderscore {
11271
fn check_local(&mut self, cx: &LateContext<'_>, local: &Local<'_>) {
113-
if in_external_macro(cx.tcx.sess, local.span) {
114-
return;
115-
}
116-
117-
if_chain! {
118-
if let PatKind::Wild = local.pat.kind;
119-
if let Some(init) = local.init;
120-
then {
121-
let init_ty = cx.typeck_results().expr_ty(init);
122-
let contains_sync_guard = init_ty.walk().any(|inner| match inner.unpack() {
123-
GenericArgKind::Type(inner_ty) => {
124-
SYNC_GUARD_SYMS
125-
.iter()
126-
.any(|&sym| is_type_diagnostic_item(cx, inner_ty, sym))
127-
|| SYNC_GUARD_PATHS.iter().any(|path| match_type(cx, inner_ty, path))
128-
},
129-
130-
GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
131-
});
132-
if contains_sync_guard {
133-
span_lint_and_help(
134-
cx,
135-
LET_UNDERSCORE_LOCK,
136-
local.span,
137-
"non-binding let on a synchronization lock",
138-
None,
139-
"consider using an underscore-prefixed named \
140-
binding or dropping explicitly with `std::mem::drop`",
141-
);
142-
} else if init_ty.needs_drop(cx.tcx, cx.param_env) {
143-
span_lint_and_help(
144-
cx,
145-
LET_UNDERSCORE_DROP,
146-
local.span,
147-
"non-binding `let` on a type that implements `Drop`",
148-
None,
149-
"consider using an underscore-prefixed named \
72+
if !in_external_macro(cx.tcx.sess, local.span)
73+
&& let PatKind::Wild = local.pat.kind
74+
&& let Some(init) = local.init
75+
{
76+
let init_ty = cx.typeck_results().expr_ty(init);
77+
let contains_sync_guard = init_ty.walk().any(|inner| match inner.unpack() {
78+
GenericArgKind::Type(inner_ty) => SYNC_GUARD_PATHS.iter().any(|path| match_type(cx, inner_ty, path)),
79+
GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
80+
});
81+
if contains_sync_guard {
82+
span_lint_and_help(
83+
cx,
84+
LET_UNDERSCORE_LOCK,
85+
local.span,
86+
"non-binding let on a synchronization lock",
87+
None,
88+
"consider using an underscore-prefixed named \
15089
binding or dropping explicitly with `std::mem::drop`",
151-
);
152-
} else if is_must_use_ty(cx, cx.typeck_results().expr_ty(init)) {
153-
span_lint_and_help(
154-
cx,
155-
LET_UNDERSCORE_MUST_USE,
156-
local.span,
157-
"non-binding let on an expression with `#[must_use]` type",
158-
None,
159-
"consider explicitly using expression value",
160-
);
161-
} else if is_must_use_func_call(cx, init) {
162-
span_lint_and_help(
163-
cx,
164-
LET_UNDERSCORE_MUST_USE,
165-
local.span,
166-
"non-binding let on a result of a `#[must_use]` function",
167-
None,
168-
"consider explicitly using function result",
169-
);
170-
}
90+
);
91+
} else if is_must_use_ty(cx, cx.typeck_results().expr_ty(init)) {
92+
span_lint_and_help(
93+
cx,
94+
LET_UNDERSCORE_MUST_USE,
95+
local.span,
96+
"non-binding let on an expression with `#[must_use]` type",
97+
None,
98+
"consider explicitly using expression value",
99+
);
100+
} else if is_must_use_func_call(cx, init) {
101+
span_lint_and_help(
102+
cx,
103+
LET_UNDERSCORE_MUST_USE,
104+
local.span,
105+
"non-binding let on a result of a `#[must_use]` function",
106+
None,
107+
"consider explicitly using function result",
108+
);
171109
}
172110
}
173111
}

‎clippy_lints/src/lib.register_lints.rs‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -214,7 +214,6 @@ store.register_lints(&[
214214
len_zero::LEN_WITHOUT_IS_EMPTY,
215215
len_zero::LEN_ZERO,
216216
let_if_seq::USELESS_LET_IF_SEQ,
217-
let_underscore::LET_UNDERSCORE_DROP,
218217
let_underscore::LET_UNDERSCORE_LOCK,
219218
let_underscore::LET_UNDERSCORE_MUST_USE,
220219
lifetimes::EXTRA_UNUSED_LIFETIMES,

‎clippy_lints/src/lib.register_pedantic.rs‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,6 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
3939
LintId::of(items_after_statements::ITEMS_AFTER_STATEMENTS),
4040
LintId::of(iter_not_returning_iterator::ITER_NOT_RETURNING_ITERATOR),
4141
LintId::of(large_stack_arrays::LARGE_STACK_ARRAYS),
42-
LintId::of(let_underscore::LET_UNDERSCORE_DROP),
4342
LintId::of(literal_representation::LARGE_DIGIT_GROUPS),
4443
LintId::of(literal_representation::UNREADABLE_LITERAL),
4544
LintId::of(loops::EXPLICIT_INTO_ITER_LOOP),

‎clippy_lints/src/renamed_lints.rs‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -11,8 +11,6 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
1111
("clippy::disallowed_method", "clippy::disallowed_methods"),
1212
("clippy::disallowed_type", "clippy::disallowed_types"),
1313
("clippy::eval_order_dependence", "clippy::mixed_read_write_in_expression"),
14-
("clippy::for_loop_over_option", "for_loops_over_fallibles"),
15-
("clippy::for_loop_over_result", "for_loops_over_fallibles"),
1614
("clippy::identity_conversion", "clippy::useless_conversion"),
1715
("clippy::if_let_some_result", "clippy::match_result_ok"),
1816
("clippy::logic_bug", "clippy::overly_complex_bool_expr"),
@@ -31,10 +29,13 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
3129
("clippy::to_string_in_display", "clippy::recursive_format_impl"),
3230
("clippy::zero_width_space", "clippy::invisible_characters"),
3331
("clippy::drop_bounds", "drop_bounds"),
32+
("clippy::for_loop_over_option", "for_loops_over_fallibles"),
33+
("clippy::for_loop_over_result", "for_loops_over_fallibles"),
3434
("clippy::for_loops_over_fallibles", "for_loops_over_fallibles"),
3535
("clippy::into_iter_on_array", "array_into_iter"),
3636
("clippy::invalid_atomic_ordering", "invalid_atomic_ordering"),
3737
("clippy::invalid_ref", "invalid_value"),
38+
("clippy::let_underscore_drop", "let_underscore_drop"),
3839
("clippy::mem_discriminant_non_enum", "enum_intrinsics_non_enums"),
3940
("clippy::panic_params", "non_fmt_panics"),
4041
("clippy::positional_named_format_parameters", "named_arguments_used_positionally"),

‎lintcheck/src/main.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -678,7 +678,7 @@ fn main() {
678678
.unwrap();
679679

680680
let server = config.recursive.then(|| {
681-
fs::remove_dir_all("target/lintcheck/shared_target_dir/recursive").unwrap_or_default();
681+
let _ = fs::remove_dir_all("target/lintcheck/shared_target_dir/recursive");
682682

683683
LintcheckServer::spawn(recursive_options)
684684
});

‎src/docs.rs‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -247,7 +247,6 @@ docs! {
247247
"len_without_is_empty",
248248
"len_zero",
249249
"let_and_return",
250-
"let_underscore_drop",
251250
"let_underscore_lock",
252251
"let_underscore_must_use",
253252
"let_unit_value",

‎src/docs/let_underscore_drop.txt‎

Lines changed: 0 additions & 29 deletions
This file was deleted.

‎src/docs/let_underscore_lock.txt‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
11
### What it does
2-
Checks for `let _ = sync_lock`.
3-
This supports `mutex` and `rwlock` in `std::sync` and `parking_lot`.
2+
Checks for `let _ = sync_lock`. This supports `mutex` and `rwlock` in
3+
`parking_lot`. For `std` locks see the `rustc` lint
4+
[`let_underscore_lock`](https://doc.rust-lang.org/nightly/rustc/lints/listing/deny-by-default.html#let-underscore-lock)
45

56
### Why is this bad?
67
This statement immediately drops the lock instead of

‎tests/ui/let_underscore_drop.rs‎

Lines changed: 0 additions & 28 deletions
This file was deleted.

‎tests/ui/let_underscore_drop.stderr‎

Lines changed: 0 additions & 27 deletions
This file was deleted.

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