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Auto merge of #6791 - TaKO8Ki:iter-count, r=matthiaskrgr

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New lint: `iter_count`

This pull request adds a new lint named `iter_count`.

---

closes https://github.com/rust-lang/rust-clippy/issues/6262

changelog: new lint `iter_count`
This commit is contained in:
bors 2021-03-02 11:31:43 +00:00
commit eb04beb005
10 changed files with 414 additions and 2 deletions
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1
CHANGELOG.md
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@ -2135,6 +2135,7 @@ Released 2018-09-13
[`invisible_characters`]: https://rust-lang.github.io/rust-clippy/master/index.html#invisible_characters
[`items_after_statements`]: https://rust-lang.github.io/rust-clippy/master/index.html#items_after_statements
[`iter_cloned_collect`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_cloned_collect
[`iter_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_count
[`iter_next_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_next_loop
[`iter_next_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_next_slice
[`iter_nth`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_nth

3
clippy_lints/src/lib.rs
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@ -775,6 +775,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&methods::INTO_ITER_ON_REF,
&methods::ITERATOR_STEP_BY_ZERO,
&methods::ITER_CLONED_COLLECT,
&methods::ITER_COUNT,
&methods::ITER_NEXT_SLICE,
&methods::ITER_NTH,
&methods::ITER_NTH_ZERO,
@ -1577,6 +1578,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&methods::INTO_ITER_ON_REF),
LintId::of(&methods::ITERATOR_STEP_BY_ZERO),
LintId::of(&methods::ITER_CLONED_COLLECT),
LintId::of(&methods::ITER_COUNT),
LintId::of(&methods::ITER_NEXT_SLICE),
LintId::of(&methods::ITER_NTH),
LintId::of(&methods::ITER_NTH_ZERO),
@ -1881,6 +1883,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&methods::FILTER_NEXT),
LintId::of(&methods::FLAT_MAP_IDENTITY),
LintId::of(&methods::INSPECT_FOR_EACH),
LintId::of(&methods::ITER_COUNT),
LintId::of(&methods::MANUAL_FILTER_MAP),
LintId::of(&methods::MANUAL_FIND_MAP),
LintId::of(&methods::OPTION_AS_REF_DEREF),

47
clippy_lints/src/methods/iter_count.rs Normal file
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@ -0,0 +1,47 @@
use crate::methods::derefs_to_slice;
use crate::utils::{is_type_diagnostic_item, match_type, paths, snippet_with_applicability, span_lint_and_sugg};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_span::sym;
use super::ITER_COUNT;
pub(crate) fn lints<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'tcx [Expr<'tcx>], iter_method: &str) {
let ty = cx.typeck_results().expr_ty(&iter_args[0]);
let caller_type = if derefs_to_slice(cx, &iter_args[0], ty).is_some() {
"slice"
} else if is_type_diagnostic_item(cx, ty, sym::vec_type) {
"Vec"
} else if is_type_diagnostic_item(cx, ty, sym!(vecdeque_type)) {
"VecDeque"
} else if is_type_diagnostic_item(cx, ty, sym!(hashset_type)) {
"HashSet"
} else if is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) {
"HashMap"
} else if match_type(cx, ty, &paths::BTREEMAP) {
"BTreeMap"
} else if match_type(cx, ty, &paths::BTREESET) {
"BTreeSet"
} else if match_type(cx, ty, &paths::LINKED_LIST) {
"LinkedList"
} else if match_type(cx, ty, &paths::BINARY_HEAP) {
"BinaryHeap"
} else {
return;
};
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
ITER_COUNT,
expr.span,
&format!("called `.{}().count()` on a `{}`", iter_method, caller_type),
"try",
format!(
"{}.len()",
snippet_with_applicability(cx, iter_args[0].span, "..", &mut applicability),
),
applicability,
);
}

31
clippy_lints/src/methods/mod.rs
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@ -4,6 +4,7 @@ mod filter_map_identity;
mod implicit_clone;
mod inefficient_to_string;
mod inspect_for_each;
mod iter_count;
mod manual_saturating_arithmetic;
mod option_map_unwrap_or;
mod unnecessary_filter_map;
@ -1540,6 +1541,32 @@ declare_clippy_lint! {
"implicitly cloning a value by invoking a function on its dereferenced type"
}
declare_clippy_lint! {
/// **What it does:** Checks for the use of `.iter().count()`.
///
/// **Why is this bad?** `.len()` is more efficient and more
/// readable.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// // Bad
/// let some_vec = vec![0, 1, 2, 3];
/// let _ = some_vec.iter().count();
/// let _ = &some_vec[..].iter().count();
///
/// // Good
/// let some_vec = vec![0, 1, 2, 3];
/// let _ = some_vec.len();
/// let _ = &some_vec[..].len();
/// ```
pub ITER_COUNT,
complexity,
"replace `.iter().count()` with `.len()`"
}
pub struct Methods {
msrv: Option<RustcVersion>,
}
@ -1585,6 +1612,7 @@ impl_lint_pass!(Methods => [
MAP_FLATTEN,
ITERATOR_STEP_BY_ZERO,
ITER_NEXT_SLICE,
ITER_COUNT,
ITER_NTH,
ITER_NTH_ZERO,
BYTES_NTH,
@ -1664,6 +1692,9 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
},
["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
["count", "into_iter"] => iter_count::lints(cx, expr, &arg_lists[1], "into_iter"),
["count", "iter"] => iter_count::lints(cx, expr, &arg_lists[1], "iter"),
["count", "iter_mut"] => iter_count::lints(cx, expr, &arg_lists[1], "iter_mut"),
["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
["nth", "bytes"] => bytes_nth::lints(cx, expr, &arg_lists[1]),

4
tests/ui/auxiliary/option_helpers.rs
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@ -48,4 +48,8 @@ impl IteratorFalsePositives {
pub fn skip_while(self) -> IteratorFalsePositives {
self
}
pub fn count(self) -> usize {
self.foo as usize
}
}

86
tests/ui/iter_count.fixed Normal file
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@ -0,0 +1,86 @@
// run-rustfix
// aux-build:option_helpers.rs
#![warn(clippy::iter_count)]
#![allow(
unused_variables,
array_into_iter,
unused_mut,
clippy::into_iter_on_ref,
clippy::unnecessary_operation
)]
extern crate option_helpers;
use option_helpers::IteratorFalsePositives;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque};
/// Struct to generate false positives for things with `.iter()`.
#[derive(Copy, Clone)]
struct HasIter;
impl HasIter {
fn iter(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
fn iter_mut(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
fn into_iter(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
}
fn main() {
let mut vec = vec![0, 1, 2, 3];
let mut boxed_slice: Box<[u8]> = Box::new([0, 1, 2, 3]);
let mut vec_deque: VecDeque<_> = vec.iter().cloned().collect();
let mut hash_set = HashSet::new();
let mut hash_map = HashMap::new();
let mut b_tree_map = BTreeMap::new();
let mut b_tree_set = BTreeSet::new();
let mut linked_list = LinkedList::new();
let mut binary_heap = BinaryHeap::new();
hash_set.insert(1);
hash_map.insert(1, 2);
b_tree_map.insert(1, 2);
b_tree_set.insert(1);
linked_list.push_back(1);
binary_heap.push(1);
&vec[..].len();
vec.len();
boxed_slice.len();
vec_deque.len();
hash_set.len();
hash_map.len();
b_tree_map.len();
b_tree_set.len();
linked_list.len();
binary_heap.len();
vec.len();
&vec[..].len();
vec_deque.len();
hash_map.len();
b_tree_map.len();
linked_list.len();
&vec[..].len();
vec.len();
vec_deque.len();
hash_set.len();
hash_map.len();
b_tree_map.len();
b_tree_set.len();
linked_list.len();
binary_heap.len();
// Make sure we don't lint for non-relevant types.
let false_positive = HasIter;
false_positive.iter().count();
false_positive.iter_mut().count();
false_positive.into_iter().count();
}

86
tests/ui/iter_count.rs Normal file
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@ -0,0 +1,86 @@
// run-rustfix
// aux-build:option_helpers.rs
#![warn(clippy::iter_count)]
#![allow(
unused_variables,
array_into_iter,
unused_mut,
clippy::into_iter_on_ref,
clippy::unnecessary_operation
)]
extern crate option_helpers;
use option_helpers::IteratorFalsePositives;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque};
/// Struct to generate false positives for things with `.iter()`.
#[derive(Copy, Clone)]
struct HasIter;
impl HasIter {
fn iter(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
fn iter_mut(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
fn into_iter(self) -> IteratorFalsePositives {
IteratorFalsePositives { foo: 0 }
}
}
fn main() {
let mut vec = vec![0, 1, 2, 3];
let mut boxed_slice: Box<[u8]> = Box::new([0, 1, 2, 3]);
let mut vec_deque: VecDeque<_> = vec.iter().cloned().collect();
let mut hash_set = HashSet::new();
let mut hash_map = HashMap::new();
let mut b_tree_map = BTreeMap::new();
let mut b_tree_set = BTreeSet::new();
let mut linked_list = LinkedList::new();
let mut binary_heap = BinaryHeap::new();
hash_set.insert(1);
hash_map.insert(1, 2);
b_tree_map.insert(1, 2);
b_tree_set.insert(1);
linked_list.push_back(1);
binary_heap.push(1);
&vec[..].iter().count();
vec.iter().count();
boxed_slice.iter().count();
vec_deque.iter().count();
hash_set.iter().count();
hash_map.iter().count();
b_tree_map.iter().count();
b_tree_set.iter().count();
linked_list.iter().count();
binary_heap.iter().count();
vec.iter_mut().count();
&vec[..].iter_mut().count();
vec_deque.iter_mut().count();
hash_map.iter_mut().count();
b_tree_map.iter_mut().count();
linked_list.iter_mut().count();
&vec[..].into_iter().count();
vec.into_iter().count();
vec_deque.into_iter().count();
hash_set.into_iter().count();
hash_map.into_iter().count();
b_tree_map.into_iter().count();
b_tree_set.into_iter().count();
linked_list.into_iter().count();
binary_heap.into_iter().count();
// Make sure we don't lint for non-relevant types.
let false_positive = HasIter;
false_positive.iter().count();
false_positive.iter_mut().count();
false_positive.into_iter().count();
}

154
tests/ui/iter_count.stderr Normal file
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@ -0,0 +1,154 @@
error: called `.iter().count()` on a `slice`
--> $DIR/iter_count.rs:53:6
|
LL | &vec[..].iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
|
= note: `-D clippy::iter-count` implied by `-D warnings`
error: called `.iter().count()` on a `Vec`
--> $DIR/iter_count.rs:54:5
|
LL | vec.iter().count();
| ^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
error: called `.iter().count()` on a `slice`
--> $DIR/iter_count.rs:55:5
|
LL | boxed_slice.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `boxed_slice.len()`
error: called `.iter().count()` on a `VecDeque`
--> $DIR/iter_count.rs:56:5
|
LL | vec_deque.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
error: called `.iter().count()` on a `HashSet`
--> $DIR/iter_count.rs:57:5
|
LL | hash_set.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_set.len()`
error: called `.iter().count()` on a `HashMap`
--> $DIR/iter_count.rs:58:5
|
LL | hash_map.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_map.len()`
error: called `.iter().count()` on a `BTreeMap`
--> $DIR/iter_count.rs:59:5
|
LL | b_tree_map.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `b_tree_map.len()`
error: called `.iter().count()` on a `BTreeSet`
--> $DIR/iter_count.rs:60:5
|
LL | b_tree_set.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `b_tree_set.len()`
error: called `.iter().count()` on a `LinkedList`
--> $DIR/iter_count.rs:61:5
|
LL | linked_list.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `linked_list.len()`
error: called `.iter().count()` on a `BinaryHeap`
--> $DIR/iter_count.rs:62:5
|
LL | binary_heap.iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `binary_heap.len()`
error: called `.iter_mut().count()` on a `Vec`
--> $DIR/iter_count.rs:64:5
|
LL | vec.iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
error: called `.iter_mut().count()` on a `slice`
--> $DIR/iter_count.rs:65:6
|
LL | &vec[..].iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
error: called `.iter_mut().count()` on a `VecDeque`
--> $DIR/iter_count.rs:66:5
|
LL | vec_deque.iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
error: called `.iter_mut().count()` on a `HashMap`
--> $DIR/iter_count.rs:67:5
|
LL | hash_map.iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_map.len()`
error: called `.iter_mut().count()` on a `BTreeMap`
--> $DIR/iter_count.rs:68:5
|
LL | b_tree_map.iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `b_tree_map.len()`
error: called `.iter_mut().count()` on a `LinkedList`
--> $DIR/iter_count.rs:69:5
|
LL | linked_list.iter_mut().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `linked_list.len()`
error: called `.into_iter().count()` on a `slice`
--> $DIR/iter_count.rs:71:6
|
LL | &vec[..].into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
error: called `.into_iter().count()` on a `Vec`
--> $DIR/iter_count.rs:72:5
|
LL | vec.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
error: called `.into_iter().count()` on a `VecDeque`
--> $DIR/iter_count.rs:73:5
|
LL | vec_deque.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
error: called `.into_iter().count()` on a `HashSet`
--> $DIR/iter_count.rs:74:5
|
LL | hash_set.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_set.len()`
error: called `.into_iter().count()` on a `HashMap`
--> $DIR/iter_count.rs:75:5
|
LL | hash_map.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_map.len()`
error: called `.into_iter().count()` on a `BTreeMap`
--> $DIR/iter_count.rs:76:5
|
LL | b_tree_map.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `b_tree_map.len()`
error: called `.into_iter().count()` on a `BTreeSet`
--> $DIR/iter_count.rs:77:5
|
LL | b_tree_set.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `b_tree_set.len()`
error: called `.into_iter().count()` on a `LinkedList`
--> $DIR/iter_count.rs:78:5
|
LL | linked_list.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `linked_list.len()`
error: called `.into_iter().count()` on a `BinaryHeap`
--> $DIR/iter_count.rs:79:5
|
LL | binary_heap.into_iter().count();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `binary_heap.len()`
error: aborting due to 25 previous errors

2
tests/ui/needless_collect.fixed
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@ -1,6 +1,6 @@
// run-rustfix
#![allow(unused, clippy::suspicious_map)]
#![allow(unused, clippy::suspicious_map, clippy::iter_count)]
use std::collections::{BTreeSet, HashMap, HashSet};

2
tests/ui/needless_collect.rs
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@ -1,6 +1,6 @@
// run-rustfix
#![allow(unused, clippy::suspicious_map)]
#![allow(unused, clippy::suspicious_map, clippy::iter_count)]
use std::collections::{BTreeSet, HashMap, HashSet};