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Suggest using Vec::extend() in same_item_push

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Using `Vec::extend(std::iter::repeat_n(item, N))` allows to use the more
natural number of elements to add `N`, as is probably done in the original
loop, instead of computing the difference between the existing number of
elements and the wanted one.

Before MSRV 1.82, the older suggestion to use `Vec::resize()` is still
issued.
This commit is contained in:
Samuel Tardieu 2025-01-11 15:14:31 +01:00
parent ab55d3fc62
commit ded9354dcf
6 changed files with 66 additions and 28 deletions
Download patch file Download diff file Expand all files Collapse all files

1
book/src/lint_configuration.md
View file

@ -767,6 +767,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
* [`ptr_as_ptr`](https://rust-lang.github.io/rust-clippy/master/index.html#ptr_as_ptr)
* [`redundant_field_names`](https://rust-lang.github.io/rust-clippy/master/index.html#redundant_field_names)
* [`redundant_static_lifetimes`](https://rust-lang.github.io/rust-clippy/master/index.html#redundant_static_lifetimes)
* [`same_item_push`](https://rust-lang.github.io/rust-clippy/master/index.html#same_item_push)
* [`seek_from_current`](https://rust-lang.github.io/rust-clippy/master/index.html#seek_from_current)
* [`seek_rewind`](https://rust-lang.github.io/rust-clippy/master/index.html#seek_rewind)
* [`transmute_ptr_to_ref`](https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ref)

1
clippy_config/src/conf.rs
View file

@ -636,6 +636,7 @@ define_Conf! {
ptr_as_ptr,
redundant_field_names,
redundant_static_lifetimes,
same_item_push,
seek_from_current,
seek_rewind,
transmute_ptr_to_ref,

2
clippy_lints/src/loops/mod.rs
View file

@ -830,7 +830,7 @@ impl Loops {
for_kv_map::check(cx, pat, arg, body);
mut_range_bound::check(cx, arg, body);
single_element_loop::check(cx, pat, arg, body, expr);
same_item_push::check(cx, pat, arg, body, expr);
same_item_push::check(cx, pat, arg, body, expr, &self.msrv);
manual_flatten::check(cx, pat, arg, body, span);
manual_find::check(cx, pat, arg, body, span, expr);
unused_enumerate_index::check(cx, pat, arg, body);

34
clippy_lints/src/loops/same_item_push.rs
View file

@ -1,8 +1,9 @@
use super::SAME_ITEM_PUSH;
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::path_to_local;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::msrvs::Msrv;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
use clippy_utils::{msrvs, path_to_local, std_or_core};
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
@ -19,19 +20,30 @@ pub(super) fn check<'tcx>(
_: &'tcx Expr<'_>,
body: &'tcx Expr<'_>,
_: &'tcx Expr<'_>,
msrv: &Msrv,
) {
fn emit_lint(cx: &LateContext<'_>, vec: &Expr<'_>, pushed_item: &Expr<'_>, ctxt: SyntaxContext) {
fn emit_lint(cx: &LateContext<'_>, vec: &Expr<'_>, pushed_item: &Expr<'_>, ctxt: SyntaxContext, msrv: &Msrv) {
let mut app = Applicability::Unspecified;
let vec_str = snippet_with_context(cx, vec.span, ctxt, "", &mut app).0;
let item_str = snippet_with_context(cx, pushed_item.span, ctxt, "", &mut app).0;
span_lint_and_help(
let secondary_help = if msrv.meets(msrvs::REPEAT_N)
&& let Some(std_or_core) = std_or_core(cx)
{
format!("or `{vec_str}.extend({std_or_core}::iter::repeat_n({item_str}, SIZE))`")
} else {
format!("or `{vec_str}.resize(NEW_SIZE, {item_str})`")
};
span_lint_and_then(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
format!("consider using vec![{item_str};SIZE] or {vec_str}.resize(NEW_SIZE, {item_str})"),
"it looks like the same item is being pushed into this `Vec`",
|diag| {
diag.help(format!("consider using `vec![{item_str};SIZE]`"))
.help(secondary_help);
},
);
}
@ -67,11 +79,11 @@ pub(super) fn check<'tcx>(
{
match init.kind {
// immutable bindings that are initialized with literal
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt),
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt, msrv),
// immutable bindings that are initialized with constant
ExprKind::Path(ref path) => {
if let Res::Def(DefKind::Const, ..) = cx.qpath_res(path, init.hir_id) {
emit_lint(cx, vec, pushed_item, ctxt);
emit_lint(cx, vec, pushed_item, ctxt, msrv);
}
},
_ => {},
@ -79,11 +91,11 @@ pub(super) fn check<'tcx>(
}
},
// constant
Res::Def(DefKind::Const, ..) => emit_lint(cx, vec, pushed_item, ctxt),
Res::Def(DefKind::Const, ..) => emit_lint(cx, vec, pushed_item, ctxt, msrv),
_ => {},
}
},
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt),
ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item, ctxt, msrv),
_ => {},
}
}

20
tests/ui/same_item_push.rs
View file

@ -21,33 +21,43 @@ fn main() {
let item = 2;
for _ in 5..=20 {
vec.push(item);
//~^ ERROR: it looks like the same item is being pushed into this Vec
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
let mut vec: Vec<u8> = Vec::new();
for _ in 0..15 {
let item = 2;
vec.push(item);
//~^ ERROR: it looks like the same item is being pushed into this Vec
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
let mut vec: Vec<u8> = Vec::new();
for _ in 0..15 {
vec.push(13);
//~^ ERROR: it looks like the same item is being pushed into this Vec
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
let mut vec = Vec::new();
for _ in 0..20 {
vec.push(VALUE);
//~^ ERROR: it looks like the same item is being pushed into this Vec
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
let mut vec = Vec::new();
let item = VALUE;
for _ in 0..20 {
vec.push(item);
//~^ ERROR: it looks like the same item is being pushed into this Vec
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
#[clippy::msrv = "1.81"]
fn older_msrv() {
let mut vec = Vec::new();
let item = VALUE;
for _ in 0..20 {
vec.push(item);
//~^ ERROR: it looks like the same item is being pushed into this `Vec`
}
}
// ** non-linted cases **

36
tests/ui/same_item_push.stderr
View file

@ -1,44 +1,58 @@
error: it looks like the same item is being pushed into this Vec
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:23:9
|
LL | vec.push(item);
| ^^^
|
= help: consider using vec![item;SIZE] or vec.resize(NEW_SIZE, item)
= help: consider using `vec![item;SIZE]`
= help: or `vec.extend(std::iter::repeat_n(item, SIZE))`
= note: `-D clippy::same-item-push` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::same_item_push)]`
error: it looks like the same item is being pushed into this Vec
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:30:9
|
LL | vec.push(item);
| ^^^
|
= help: consider using vec![item;SIZE] or vec.resize(NEW_SIZE, item)
= help: consider using `vec![item;SIZE]`
= help: or `vec.extend(std::iter::repeat_n(item, SIZE))`
error: it looks like the same item is being pushed into this Vec
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:36:9
|
LL | vec.push(13);
| ^^^
|
= help: consider using vec![13;SIZE] or vec.resize(NEW_SIZE, 13)
= help: consider using `vec![13;SIZE]`
= help: or `vec.extend(std::iter::repeat_n(13, SIZE))`
error: it looks like the same item is being pushed into this Vec
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:42:9
|
LL | vec.push(VALUE);
| ^^^
|
= help: consider using vec![VALUE;SIZE] or vec.resize(NEW_SIZE, VALUE)
= help: consider using `vec![VALUE;SIZE]`
= help: or `vec.extend(std::iter::repeat_n(VALUE, SIZE))`
error: it looks like the same item is being pushed into this Vec
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:49:9
|
LL | vec.push(item);
| ^^^
|
= help: consider using vec![item;SIZE] or vec.resize(NEW_SIZE, item)
= help: consider using `vec![item;SIZE]`
= help: or `vec.extend(std::iter::repeat_n(item, SIZE))`
error: aborting due to 5 previous errors
error: it looks like the same item is being pushed into this `Vec`
--> tests/ui/same_item_push.rs:58:13
|
LL | vec.push(item);
| ^^^
|
= help: consider using `vec![item;SIZE]`
= help: or `vec.resize(NEW_SIZE, item)`
error: aborting due to 6 previous errors