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Auto merge of #4348 - phansch:deprecate-unused-unused-collect, r=flip1995
Deprecate unused_collect lint I found this because we only had two test cases in total for this lint. It turns out the functionality is fully covered by rustc these days. [Playground Examples](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=eb8ee6db389c77180c9fb152d3c608f4) changelog: Deprecate `unused_collect` lint. This is fully covered by rustc's `#[must_use]` on `collect` cc #2846
2 parents 33ec66a + 42f0353 commit a3da66d

11 files changed

+45
-98
lines changed

‎README.md

+1-1
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66

77
A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
88

9-
[There are 310 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
9+
[There are 309 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
1010

1111
We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
1212

‎clippy_lints/src/deprecated_lints.rs

+8
Original file line numberDiff line numberDiff line change
@@ -122,3 +122,11 @@ declare_deprecated_lint! {
122122
pub INVALID_REF,
123123
"superseded by rustc lint `invalid_value`"
124124
}
125+
126+
/// **What it does:** Nothing. This lint has been deprecated.
127+
///
128+
/// **Deprecation reason:** This lint has been superseded by #[must_use] in rustc.
129+
declare_deprecated_lint! {
130+
pub UNUSED_COLLECT,
131+
"`collect` has been marked as #[must_use] in rustc and that covers all cases of this lint"
132+
}

‎clippy_lints/src/lib.rs

+4-2
Original file line numberDiff line numberDiff line change
@@ -435,6 +435,10 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
435435
"clippy::invalid_ref",
436436
"superseded by rustc lint `invalid_value`",
437437
);
438+
store.register_removed(
439+
"clippy::unused_collect",
440+
"`collect` has been marked as #[must_use] in rustc and that covers all cases of this lint",
441+
);
438442
// end deprecated lints, do not remove this comment, it’s used in `update_lints`
439443

440444
reg.register_late_lint_pass(box serde_api::SerdeAPI);
@@ -761,7 +765,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
761765
loops::NEEDLESS_RANGE_LOOP,
762766
loops::NEVER_LOOP,
763767
loops::REVERSE_RANGE_LOOP,
764-
loops::UNUSED_COLLECT,
765768
loops::WHILE_IMMUTABLE_CONDITION,
766769
loops::WHILE_LET_LOOP,
767770
loops::WHILE_LET_ON_ITERATOR,
@@ -1142,7 +1145,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
11421145
large_enum_variant::LARGE_ENUM_VARIANT,
11431146
loops::MANUAL_MEMCPY,
11441147
loops::NEEDLESS_COLLECT,
1145-
loops::UNUSED_COLLECT,
11461148
methods::EXPECT_FUN_CALL,
11471149
methods::ITER_NTH,
11481150
methods::OR_FUN_CALL,

‎clippy_lints/src/loops.rs

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Original file line numberDiff line numberDiff line change
@@ -242,24 +242,6 @@ declare_clippy_lint! {
242242
"`loop { if let { ... } else break }`, which can be written as a `while let` loop"
243243
}
244244

245-
declare_clippy_lint! {
246-
/// **What it does:** Checks for using `collect()` on an iterator without using
247-
/// the result.
248-
///
249-
/// **Why is this bad?** It is more idiomatic to use a `for` loop over the
250-
/// iterator instead.
251-
///
252-
/// **Known problems:** None.
253-
///
254-
/// **Example:**
255-
/// ```ignore
256-
/// vec.iter().map(|x| /* some operation returning () */).collect::<Vec<_>>();
257-
/// ```
258-
pub UNUSED_COLLECT,
259-
perf,
260-
"`collect()`ing an iterator without using the result; this is usually better written as a for loop"
261-
}
262-
263245
declare_clippy_lint! {
264246
/// **What it does:** Checks for functions collecting an iterator when collect
265247
/// is not needed.
@@ -467,7 +449,6 @@ declare_lint_pass!(Loops => [
467449
FOR_LOOP_OVER_RESULT,
468450
FOR_LOOP_OVER_OPTION,
469451
WHILE_LET_LOOP,
470-
UNUSED_COLLECT,
471452
NEEDLESS_COLLECT,
472453
REVERSE_RANGE_LOOP,
473454
EXPLICIT_COUNTER_LOOP,
@@ -602,25 +583,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Loops {
602583

603584
check_needless_collect(expr, cx);
604585
}
605-
606-
fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
607-
if let StmtKind::Semi(ref expr) = stmt.node {
608-
if let ExprKind::MethodCall(ref method, _, ref args) = expr.node {
609-
if args.len() == 1
610-
&& method.ident.name == sym!(collect)
611-
&& match_trait_method(cx, expr, &paths::ITERATOR)
612-
{
613-
span_lint(
614-
cx,
615-
UNUSED_COLLECT,
616-
expr.span,
617-
"you are collect()ing an iterator and throwing away the result. \
618-
Consider using an explicit for loop to exhaust the iterator",
619-
);
620-
}
621-
}
622-
}
623-
}
624586
}
625587

626588
enum NeverLoopResult {

‎src/lintlist/mod.rs

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Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@ pub use lint::Lint;
66
pub use lint::LINT_LEVELS;
77

88
// begin lint list, do not remove this comment, it’s used in `update_lints`
9-
pub const ALL_LINTS: [Lint; 310] = [
9+
pub const ALL_LINTS: [Lint; 309] = [
1010
Lint {
1111
name: "absurd_extreme_comparisons",
1212
group: "correctness",
@@ -1967,13 +1967,6 @@ pub const ALL_LINTS: [Lint; 310] = [
19671967
deprecation: None,
19681968
module: "misc_early",
19691969
},
1970-
Lint {
1971-
name: "unused_collect",
1972-
group: "perf",
1973-
desc: "`collect()`ing an iterator without using the result; this is usually better written as a for loop",
1974-
deprecation: None,
1975-
module: "loops",
1976-
},
19771970
Lint {
19781971
name: "unused_io_amount",
19791972
group: "correctness",

‎tests/ui/deprecated.stderr

+7-1
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,12 @@ error: lint `clippy::misaligned_transmute` has been removed: `this lint has been
3030
LL | #[warn(clippy::misaligned_transmute)]
3131
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3232

33+
error: lint `clippy::unused_collect` has been removed: ``collect` has been marked as #[must_use] in rustc and that covers all cases of this lint`
34+
--> $DIR/deprecated.rs:6:8
35+
|
36+
LL | #[warn(clippy::unused_collect)]
37+
| ^^^^^^^^^^^^^^^^^^^^^^
38+
3339
error: lint `clippy::invalid_ref` has been removed: `superseded by rustc lint `invalid_value``
3440
--> $DIR/deprecated.rs:7:8
3541
|
@@ -42,5 +48,5 @@ error: lint `clippy::str_to_string` has been removed: `using `str::to_string` is
4248
LL | #[warn(clippy::str_to_string)]
4349
| ^^^^^^^^^^^^^^^^^^^^^
4450

45-
error: aborting due to 7 previous errors
51+
error: aborting due to 8 previous errors
4652

‎tests/ui/deprecated_old.rs

-1
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,5 @@
33
#[warn(unstable_as_slice)]
44
#[warn(unstable_as_mut_slice)]
55
#[warn(misaligned_transmute)]
6-
#[warn(unused_collect)]
76

87
fn main() {}

‎tests/ui/deprecated_old.stderr

+1-7
Original file line numberDiff line numberDiff line change
@@ -30,17 +30,11 @@ error: lint `misaligned_transmute` has been removed: `this lint has been split i
3030
LL | #[warn(misaligned_transmute)]
3131
| ^^^^^^^^^^^^^^^^^^^^
3232

33-
error: lint name `unused_collect` is deprecated and may not have an effect in the future. Also `cfg_attr(cargo-clippy)` won't be necessary anymore
34-
--> $DIR/deprecated_old.rs:6:8
35-
|
36-
LL | #[warn(unused_collect)]
37-
| ^^^^^^^^^^^^^^ help: change it to: `clippy::unused_collect`
38-
3933
error: lint `str_to_string` has been removed: `using `str::to_string` is common even today and specialization will likely happen soon`
4034
--> $DIR/deprecated_old.rs:1:8
4135
|
4236
LL | #[warn(str_to_string)]
4337
| ^^^^^^^^^^^^^
4438

45-
error: aborting due to 7 previous errors
39+
error: aborting due to 6 previous errors
4640

‎tests/ui/for_loop.rs

-1
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,6 @@ impl Unrelated {
2424
clippy::reverse_range_loop,
2525
clippy::for_kv_map
2626
)]
27-
#[warn(clippy::unused_collect)]
2827
#[allow(
2928
clippy::linkedlist,
3029
clippy::shadow_unrelated,

‎tests/ui/for_loop.stderr

+22-30
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
error: this range is empty so this for loop will never run
2-
--> $DIR/for_loop.rs:40:14
2+
--> $DIR/for_loop.rs:39:14
33
|
44
LL | for i in 10..0 {
55
| ^^^^^
@@ -11,7 +11,7 @@ LL | for i in (0..10).rev() {
1111
| ^^^^^^^^^^^^^
1212

1313
error: this range is empty so this for loop will never run
14-
--> $DIR/for_loop.rs:44:14
14+
--> $DIR/for_loop.rs:43:14
1515
|
1616
LL | for i in 10..=0 {
1717
| ^^^^^^
@@ -21,7 +21,7 @@ LL | for i in (0...10).rev() {
2121
| ^^^^^^^^^^^^^^
2222

2323
error: this range is empty so this for loop will never run
24-
--> $DIR/for_loop.rs:48:14
24+
--> $DIR/for_loop.rs:47:14
2525
|
2626
LL | for i in MAX_LEN..0 {
2727
| ^^^^^^^^^^
@@ -31,13 +31,13 @@ LL | for i in (0..MAX_LEN).rev() {
3131
| ^^^^^^^^^^^^^^^^^^
3232

3333
error: this range is empty so this for loop will never run
34-
--> $DIR/for_loop.rs:52:14
34+
--> $DIR/for_loop.rs:51:14
3535
|
3636
LL | for i in 5..5 {
3737
| ^^^^
3838

3939
error: this range is empty so this for loop will never run
40-
--> $DIR/for_loop.rs:77:14
40+
--> $DIR/for_loop.rs:76:14
4141
|
4242
LL | for i in 10..5 + 4 {
4343
| ^^^^^^^^^
@@ -47,7 +47,7 @@ LL | for i in (5 + 4..10).rev() {
4747
| ^^^^^^^^^^^^^^^^^
4848

4949
error: this range is empty so this for loop will never run
50-
--> $DIR/for_loop.rs:81:14
50+
--> $DIR/for_loop.rs:80:14
5151
|
5252
LL | for i in (5 + 2)..(3 - 1) {
5353
| ^^^^^^^^^^^^^^^^
@@ -57,108 +57,100 @@ LL | for i in ((3 - 1)..(5 + 2)).rev() {
5757
| ^^^^^^^^^^^^^^^^^^^^^^^^
5858

5959
error: this range is empty so this for loop will never run
60-
--> $DIR/for_loop.rs:85:14
60+
--> $DIR/for_loop.rs:84:14
6161
|
6262
LL | for i in (5 + 2)..(8 - 1) {
6363
| ^^^^^^^^^^^^^^^^
6464

6565
error: it is more concise to loop over references to containers instead of using explicit iteration methods
66-
--> $DIR/for_loop.rs:107:15
66+
--> $DIR/for_loop.rs:106:15
6767
|
6868
LL | for _v in vec.iter() {}
6969
| ^^^^^^^^^^ help: to write this more concisely, try: `&vec`
7070
|
7171
= note: `-D clippy::explicit-iter-loop` implied by `-D warnings`
7272

7373
error: it is more concise to loop over references to containers instead of using explicit iteration methods
74-
--> $DIR/for_loop.rs:109:15
74+
--> $DIR/for_loop.rs:108:15
7575
|
7676
LL | for _v in vec.iter_mut() {}
7777
| ^^^^^^^^^^^^^^ help: to write this more concisely, try: `&mut vec`
7878

7979
error: it is more concise to loop over containers instead of using explicit iteration methods`
80-
--> $DIR/for_loop.rs:112:15
80+
--> $DIR/for_loop.rs:111:15
8181
|
8282
LL | for _v in out_vec.into_iter() {}
8383
| ^^^^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `out_vec`
8484
|
8585
= note: `-D clippy::explicit-into-iter-loop` implied by `-D warnings`
8686

8787
error: it is more concise to loop over references to containers instead of using explicit iteration methods
88-
--> $DIR/for_loop.rs:115:15
88+
--> $DIR/for_loop.rs:114:15
8989
|
9090
LL | for _v in array.into_iter() {}
9191
| ^^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `&array`
9292

9393
error: it is more concise to loop over references to containers instead of using explicit iteration methods
94-
--> $DIR/for_loop.rs:120:15
94+
--> $DIR/for_loop.rs:119:15
9595
|
9696
LL | for _v in [1, 2, 3].iter() {}
9797
| ^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `&[1, 2, 3]`
9898

9999
error: it is more concise to loop over references to containers instead of using explicit iteration methods
100-
--> $DIR/for_loop.rs:124:15
100+
--> $DIR/for_loop.rs:123:15
101101
|
102102
LL | for _v in [0; 32].iter() {}
103103
| ^^^^^^^^^^^^^^ help: to write this more concisely, try: `&[0; 32]`
104104

105105
error: it is more concise to loop over references to containers instead of using explicit iteration methods
106-
--> $DIR/for_loop.rs:129:15
106+
--> $DIR/for_loop.rs:128:15
107107
|
108108
LL | for _v in ll.iter() {}
109109
| ^^^^^^^^^ help: to write this more concisely, try: `&ll`
110110

111111
error: it is more concise to loop over references to containers instead of using explicit iteration methods
112-
--> $DIR/for_loop.rs:132:15
112+
--> $DIR/for_loop.rs:131:15
113113
|
114114
LL | for _v in vd.iter() {}
115115
| ^^^^^^^^^ help: to write this more concisely, try: `&vd`
116116

117117
error: it is more concise to loop over references to containers instead of using explicit iteration methods
118-
--> $DIR/for_loop.rs:135:15
118+
--> $DIR/for_loop.rs:134:15
119119
|
120120
LL | for _v in bh.iter() {}
121121
| ^^^^^^^^^ help: to write this more concisely, try: `&bh`
122122

123123
error: it is more concise to loop over references to containers instead of using explicit iteration methods
124-
--> $DIR/for_loop.rs:138:15
124+
--> $DIR/for_loop.rs:137:15
125125
|
126126
LL | for _v in hm.iter() {}
127127
| ^^^^^^^^^ help: to write this more concisely, try: `&hm`
128128

129129
error: it is more concise to loop over references to containers instead of using explicit iteration methods
130-
--> $DIR/for_loop.rs:141:15
130+
--> $DIR/for_loop.rs:140:15
131131
|
132132
LL | for _v in bt.iter() {}
133133
| ^^^^^^^^^ help: to write this more concisely, try: `&bt`
134134

135135
error: it is more concise to loop over references to containers instead of using explicit iteration methods
136-
--> $DIR/for_loop.rs:144:15
136+
--> $DIR/for_loop.rs:143:15
137137
|
138138
LL | for _v in hs.iter() {}
139139
| ^^^^^^^^^ help: to write this more concisely, try: `&hs`
140140

141141
error: it is more concise to loop over references to containers instead of using explicit iteration methods
142-
--> $DIR/for_loop.rs:147:15
142+
--> $DIR/for_loop.rs:146:15
143143
|
144144
LL | for _v in bs.iter() {}
145145
| ^^^^^^^^^ help: to write this more concisely, try: `&bs`
146146

147147
error: you are iterating over `Iterator::next()` which is an Option; this will compile but is probably not what you want
148-
--> $DIR/for_loop.rs:149:15
148+
--> $DIR/for_loop.rs:148:15
149149
|
150150
LL | for _v in vec.iter().next() {}
151151
| ^^^^^^^^^^^^^^^^^
152152
|
153153
= note: `-D clippy::iter-next-loop` implied by `-D warnings`
154154

155-
error: you are collect()ing an iterator and throwing away the result. Consider using an explicit for loop to exhaust the iterator
156-
--> $DIR/for_loop.rs:156:5
157-
|
158-
LL | vec.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>();
159-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
160-
|
161-
= note: `-D clippy::unused-collect` implied by `-D warnings`
162-
163-
error: aborting due to 22 previous errors
155+
error: aborting due to 21 previous errors
164156

‎tests/ui/infinite_iter.stderr

+1-9
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,3 @@
1-
error: you are collect()ing an iterator and throwing away the result. Consider using an explicit for loop to exhaust the iterator
2-
--> $DIR/infinite_iter.rs:10:5
3-
|
4-
LL | repeat(0_u8).collect::<Vec<_>>(); // infinite iter
5-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
6-
|
7-
= note: `-D clippy::unused-collect` implied by `-D warnings`
8-
91
error: infinite iteration detected
102
--> $DIR/infinite_iter.rs:10:5
113
|
@@ -113,5 +105,5 @@ LL | let _: HashSet<i32> = (0..).collect(); // Infinite iter
113105
|
114106
= note: `#[deny(clippy::infinite_iter)]` on by default
115107

116-
error: aborting due to 15 previous errors
108+
error: aborting due to 14 previous errors
117109

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