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add a lint for redundant repeat().take()
1 parent 0f9cc8d commit 33a5b21

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+147
-16
lines changed

‎CHANGELOG.md

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@@ -5954,6 +5954,7 @@ Released 2018-09-13
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[`redundant_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pattern
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[`redundant_pattern_matching`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pattern_matching
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[`redundant_pub_crate`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pub_crate
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[`redundant_repeat_take`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_repeat_take
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[`redundant_slicing`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_slicing
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[`redundant_static_lifetimes`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_static_lifetimes
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[`redundant_type_annotations`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_type_annotations

‎clippy_lints/src/declared_lints.rs

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@@ -456,6 +456,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
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crate::methods::READONLY_WRITE_LOCK_INFO,
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crate::methods::READ_LINE_WITHOUT_TRIM_INFO,
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crate::methods::REDUNDANT_AS_STR_INFO,
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crate::methods::REDUNDANT_REPEAT_TAKE_INFO,
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crate::methods::REPEAT_ONCE_INFO,
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crate::methods::RESULT_FILTER_MAP_INFO,
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crate::methods::RESULT_MAP_OR_INTO_OPTION_INFO,

‎clippy_lints/src/methods/mod.rs

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@@ -91,6 +91,7 @@ mod range_zip_with_len;
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mod read_line_without_trim;
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mod readonly_write_lock;
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mod redundant_as_str;
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mod redundant_repeat_take;
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mod repeat_once;
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mod result_map_or_else_none;
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mod search_is_some;
@@ -4284,6 +4285,29 @@ declare_clippy_lint! {
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"map of a trivial closure (not dependent on parameter) over a range"
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}
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declare_clippy_lint! {
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/// ### What it does
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///
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/// Checks for `repeat().take()` that can be replaced with `repeat_n()`.
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///
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/// ### Why is this bad?
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///
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/// Using `repeat_n()` is more concise and clearer.
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///
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/// ### Example
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/// ```no_run
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/// let _ = std::iter::repeat(10).take(3);
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/// ```
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/// Use instead:
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/// ```no_run
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/// let _ = std::iter::repeat_n(10, 3);
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/// ```
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#[clippy::version = "1.85.0"]
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pub REDUNDANT_REPEAT_TAKE,
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style,
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"detect `repeat().take()` that can be replaced with `repeat_n()`"
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}
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pub struct Methods {
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avoid_breaking_exported_api: bool,
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msrv: Msrv,
@@ -4449,6 +4473,7 @@ impl_lint_pass!(Methods => [
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MAP_ALL_ANY_IDENTITY,
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MAP_WITH_UNUSED_ARGUMENT_OVER_RANGES,
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UNNECESSARY_MAP_OR,
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REDUNDANT_REPEAT_TAKE,
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]);
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/// Extracts a method call name, args, and `Span` of the method name.
@@ -5117,6 +5142,7 @@ impl Methods {
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("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
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("take", [arg]) => {
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iter_out_of_bounds::check_take(cx, expr, recv, arg);
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redundant_repeat_take::check(cx, expr, recv, arg);
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if let Some(("cloned", recv2, [], _span2, _)) = method_call(recv) {
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iter_overeager_cloned::check(
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cx,

‎clippy_lints/src/methods/redundant_repeat_take.rs

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@@ -0,0 +1,32 @@
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, QPath};
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use rustc_lint::LateContext;
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use super::REDUNDANT_REPEAT_TAKE;
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pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, repeat_expr: &Expr<'_>, take_arg: &Expr<'_>) {
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if !expr.span.from_expansion()
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&& let ExprKind::Call(inner, repeat_args) = repeat_expr.kind
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&& repeat_args.len() == 1
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&& let ExprKind::Path(ref qpath) = inner.kind
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&& let QPath::Resolved(_, path) = qpath
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&& path.segments.len() == 1
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&& path.segments[0].ident.name.as_str() == "repeat"
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{
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span_lint_and_sugg(
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cx,
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REDUNDANT_REPEAT_TAKE,
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expr.span,
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"redundant `repeat().take()`",
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"consider using `repeat_n()` instead",
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format!(
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"std::iter::repeat_n({}, {})",
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snippet(cx, repeat_args[0].span, ""),
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snippet(cx, take_arg.span, "")
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),
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Applicability::MachineApplicable,
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);
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}
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}

‎clippy_utils/src/lib.rs

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@@ -15,6 +15,7 @@
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clippy::missing_errors_doc,
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clippy::missing_panics_doc,
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clippy::must_use_candidate,
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clippy::redundant_repeat_take,
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rustc::diagnostic_outside_of_impl,
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rustc::untranslatable_diagnostic
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)]

‎tests/ui/manual_str_repeat.fixed

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@@ -1,4 +1,4 @@
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#![allow(non_local_definitions)]
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#![allow(non_local_definitions, clippy::redundant_repeat_take)]
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#![warn(clippy::manual_str_repeat)]
33

44
use std::borrow::Cow;

‎tests/ui/manual_str_repeat.rs

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@@ -1,4 +1,4 @@
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#![allow(non_local_definitions)]
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#![allow(non_local_definitions, redundant_repeat_take)]
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#![warn(clippy::manual_str_repeat)]
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use std::borrow::Cow;

‎tests/ui/manual_str_repeat.stderr

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@@ -1,3 +1,28 @@
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error: lint name `redundant_repeat_take` is deprecated and may not have an effect in the future
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--> tests/ui/manual_str_repeat.rs:1:33
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|
4+
LL | #![allow(non_local_definitions, redundant_repeat_take)]
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| ^^^^^^^^^^^^^^^^^^^^^ help: change it to: `clippy::redundant_repeat_take`
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|
7+
= note: `-D renamed-and-removed-lints` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(renamed_and_removed_lints)]`
9+
10+
error: lint name `redundant_repeat_take` is deprecated and may not have an effect in the future
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--> tests/ui/manual_str_repeat.rs:1:33
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|
13+
LL | #![allow(non_local_definitions, redundant_repeat_take)]
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| ^^^^^^^^^^^^^^^^^^^^^ help: change it to: `clippy::redundant_repeat_take`
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|
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= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
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error: lint name `redundant_repeat_take` is deprecated and may not have an effect in the future
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--> tests/ui/manual_str_repeat.rs:1:33
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|
21+
LL | #![allow(non_local_definitions, redundant_repeat_take)]
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| ^^^^^^^^^^^^^^^^^^^^^ help: change it to: `clippy::redundant_repeat_take`
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|
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= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
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error: manual implementation of `str::repeat` using iterators
227
--> tests/ui/manual_str_repeat.rs:8:21
328
|
@@ -61,5 +86,5 @@ error: manual implementation of `str::repeat` using iterators
6186
LL | let _: String = std::iter::repeat("test").take(10).collect();
6287
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `"test".repeat(10)`
6388

64-
error: aborting due to 10 previous errors
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error: aborting due to 13 previous errors
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‎tests/ui/redundant_repeat_take.fixed

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@@ -0,0 +1,13 @@
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#![warn(clippy::redundant_repeat_take)]
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use std::iter::repeat;
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5+
fn main() {
6+
let _ = std::iter::repeat_n(10, 3);
7+
8+
let _ = std::iter::repeat_n(String::from("foo"), 4);
9+
10+
for value in std::iter::repeat(5).take(3) {}
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12+
let _: Vec<_> = std::iter::repeat(String::from("bar")).take(10).collect();
13+
}

‎tests/ui/redundant_repeat_take.rs

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@@ -0,0 +1,13 @@
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#![warn(clippy::redundant_repeat_take)]
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3+
use std::iter::repeat;
4+
5+
fn main() {
6+
let _ = repeat(10).take(3);
7+
8+
let _ = repeat(String::from("foo")).take(4);
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10+
for value in std::iter::repeat(5).take(3) {}
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let _: Vec<_> = std::iter::repeat(String::from("bar")).take(10).collect();
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}

‎tests/ui/redundant_repeat_take.stderr

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@@ -0,0 +1,17 @@
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error: redundant `repeat().take()`
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--> tests/ui/redundant_repeat_take.rs:6:13
3+
|
4+
LL | let _ = repeat(10).take(3);
5+
| ^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(10, 3)`
6+
|
7+
= note: `-D clippy::redundant-repeat-take` implied by `-D warnings`
8+
= help: to override `-D warnings` add `#[allow(clippy::redundant_repeat_take)]`
9+
10+
error: redundant `repeat().take()`
11+
--> tests/ui/redundant_repeat_take.rs:8:13
12+
|
13+
LL | let _ = repeat(String::from("foo")).take(4);
14+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(String::from("foo"), 4)`
15+
16+
error: aborting due to 2 previous errors
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‎tests/ui/slow_vector_initialization.rs

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@@ -1,3 +1,5 @@
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#![allow(clippy::redundant_repeat_take)]
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//@no-rustfix
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use std::iter::repeat;
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fn main() {

‎tests/ui/slow_vector_initialization.stderr

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@@ -1,5 +1,5 @@
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error: slow zero-filling initialization
2-
--> tests/ui/slow_vector_initialization.rs:14:5
2+
--> tests/ui/slow_vector_initialization.rs:16:5
33
|
44
LL | let mut vec1 = Vec::with_capacity(len);
55
| ----------------------- help: consider replacing this with: `vec![0; len]`
@@ -10,95 +10,95 @@ LL | vec1.extend(repeat(0).take(len));
1010
= help: to override `-D warnings` add `#[allow(clippy::slow_vector_initialization)]`
1111

1212
error: slow zero-filling initialization
13-
--> tests/ui/slow_vector_initialization.rs:20:5
13+
--> tests/ui/slow_vector_initialization.rs:22:5
1414
|
1515
LL | let mut vec2 = Vec::with_capacity(len - 10);
1616
| ---------------------------- help: consider replacing this with: `vec![0; len - 10]`
1717
LL | vec2.extend(repeat(0).take(len - 10));
1818
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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2020
error: slow zero-filling initialization
21-
--> tests/ui/slow_vector_initialization.rs:28:5
21+
--> tests/ui/slow_vector_initialization.rs:30:5
2222
|
2323
LL | let mut vec4 = Vec::with_capacity(len);
2424
| ----------------------- help: consider replacing this with: `vec![0; len]`
2525
LL | vec4.extend(repeat(0).take(vec4.capacity()));
2626
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2727

2828
error: slow zero-filling initialization
29-
--> tests/ui/slow_vector_initialization.rs:39:5
29+
--> tests/ui/slow_vector_initialization.rs:41:5
3030
|
3131
LL | let mut resized_vec = Vec::with_capacity(30);
3232
| ---------------------- help: consider replacing this with: `vec![0; 30]`
3333
LL | resized_vec.resize(30, 0);
3434
| ^^^^^^^^^^^^^^^^^^^^^^^^^
3535

3636
error: slow zero-filling initialization
37-
--> tests/ui/slow_vector_initialization.rs:43:5
37+
--> tests/ui/slow_vector_initialization.rs:45:5
3838
|
3939
LL | let mut extend_vec = Vec::with_capacity(30);
4040
| ---------------------- help: consider replacing this with: `vec![0; 30]`
4141
LL | extend_vec.extend(repeat(0).take(30));
4242
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4343

4444
error: slow zero-filling initialization
45-
--> tests/ui/slow_vector_initialization.rs:51:5
45+
--> tests/ui/slow_vector_initialization.rs:53:5
4646
|
4747
LL | let mut vec1 = Vec::with_capacity(len);
4848
| ----------------------- help: consider replacing this with: `vec![0; len]`
4949
LL | vec1.resize(len, 0);
5050
| ^^^^^^^^^^^^^^^^^^^
5151

5252
error: slow zero-filling initialization
53-
--> tests/ui/slow_vector_initialization.rs:60:5
53+
--> tests/ui/slow_vector_initialization.rs:62:5
5454
|
5555
LL | let mut vec3 = Vec::with_capacity(len - 10);
5656
| ---------------------------- help: consider replacing this with: `vec![0; len - 10]`
5757
LL | vec3.resize(len - 10, 0);
5858
| ^^^^^^^^^^^^^^^^^^^^^^^^
5959

6060
error: slow zero-filling initialization
61-
--> tests/ui/slow_vector_initialization.rs:64:5
61+
--> tests/ui/slow_vector_initialization.rs:66:5
6262
|
6363
LL | let mut vec4 = Vec::with_capacity(len);
6464
| ----------------------- help: consider replacing this with: `vec![0; len]`
6565
LL | vec4.resize(vec4.capacity(), 0);
6666
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
6767

6868
error: slow zero-filling initialization
69-
--> tests/ui/slow_vector_initialization.rs:69:5
69+
--> tests/ui/slow_vector_initialization.rs:71:5
7070
|
7171
LL | vec1 = Vec::with_capacity(10);
7272
| ---------------------- help: consider replacing this with: `vec![0; 10]`
7373
LL | vec1.resize(10, 0);
7474
| ^^^^^^^^^^^^^^^^^^
7575

7676
error: slow zero-filling initialization
77-
--> tests/ui/slow_vector_initialization.rs:77:5
77+
--> tests/ui/slow_vector_initialization.rs:79:5
7878
|
7979
LL | let mut vec1 = Vec::new();
8080
| ---------- help: consider replacing this with: `vec![0; len]`
8181
LL | vec1.resize(len, 0);
8282
| ^^^^^^^^^^^^^^^^^^^
8383

8484
error: slow zero-filling initialization
85-
--> tests/ui/slow_vector_initialization.rs:82:5
85+
--> tests/ui/slow_vector_initialization.rs:84:5
8686
|
8787
LL | let mut vec3 = Vec::new();
8888
| ---------- help: consider replacing this with: `vec![0; len - 10]`
8989
LL | vec3.resize(len - 10, 0);
9090
| ^^^^^^^^^^^^^^^^^^^^^^^^
9191

9292
error: slow zero-filling initialization
93-
--> tests/ui/slow_vector_initialization.rs:87:5
93+
--> tests/ui/slow_vector_initialization.rs:89:5
9494
|
9595
LL | vec1 = Vec::new();
9696
| ---------- help: consider replacing this with: `vec![0; 10]`
9797
LL | vec1.resize(10, 0);
9898
| ^^^^^^^^^^^^^^^^^^
9999

100100
error: slow zero-filling initialization
101-
--> tests/ui/slow_vector_initialization.rs:91:5
101+
--> tests/ui/slow_vector_initialization.rs:93:5
102102
|
103103
LL | vec1 = vec![];
104104
| ------ help: consider replacing this with: `vec![0; 10]`

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