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Restrict same_item_push to suppress false positives

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It emits a lint when the pushed item is a literal, a constant and an immutable binding that are initialized with those.
This commit is contained in:
Takayuki Nakata 2020-09-07 22:17:31 +09:00
parent daad592fac
commit 3d30ef7818
3 changed files with 97 additions and 33 deletions
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83
clippy_lints/src/loops.rs
View file

@ -1153,27 +1153,70 @@ fn detect_same_item_push<'tcx>(
let vec_str = snippet_with_macro_callsite(cx, vec.span, "");
let item_str = snippet_with_macro_callsite(cx, pushed_item.span, "");
if let ExprKind::Path(ref qpath) = pushed_item.kind {
if_chain! {
if let Res::Local(hir_id) = qpath_res(cx, qpath, pushed_item.hir_id);
let node = cx.tcx.hir().get(hir_id);
if let Node::Binding(pat) = node;
if let PatKind::Binding(bind_ann, ..) = pat.kind;
if !matches!(bind_ann, BindingAnnotation::RefMut | BindingAnnotation::Mutable);
then {
span_lint_and_help(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
&format!(
"try using vec![{};SIZE] or {}.resize(NEW_SIZE, {})",
item_str, vec_str, item_str
),
)
}
match qpath_res(cx, qpath, pushed_item.hir_id) {
// immutable bindings that are initialized with literal or constant
Res::Local(hir_id) => {
if_chain! {
let node = cx.tcx.hir().get(hir_id);
if let Node::Binding(pat) = node;
if let PatKind::Binding(bind_ann, ..) = pat.kind;
if !matches!(bind_ann, BindingAnnotation::RefMut | BindingAnnotation::Mutable);
let parent_node = cx.tcx.hir().get_parent_node(hir_id);
if let Some(Node::Local(parent_let_expr)) = cx.tcx.hir().find(parent_node);
if let rustc_hir::Local { init: Some(init), .. } = parent_let_expr;
then {
match init.kind {
// immutable bindings that are initialized with literal
ExprKind::Lit(..) => {
span_lint_and_help(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
&format!(
"try using vec![{};SIZE] or {}.resize(NEW_SIZE, {})",
item_str, vec_str, item_str
),
)
},
// immutable bindings that are initialized with constant
ExprKind::Path(ref path) => {
if let Res::Def(DefKind::Const, ..) = qpath_res(cx, path, init.hir_id) {
span_lint_and_help(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
&format!(
"try using vec![{};SIZE] or {}.resize(NEW_SIZE, {})",
item_str, vec_str, item_str
),
)
}
}
_ => {},
}
}
}
},
// constant
Res::Def(DefKind::Const, ..) => span_lint_and_help(
cx,
SAME_ITEM_PUSH,
vec.span,
"it looks like the same item is being pushed into this Vec",
None,
&format!(
"try using vec![{};SIZE] or {}.resize(NEW_SIZE, {})",
item_str, vec_str, item_str
),
),
_ => {},
}
} else if mutated_variables(pushed_item, cx).map_or(false, |mutvars| mutvars.is_empty()) {
} else if let ExprKind::Lit(..) = pushed_item.kind {
// literal
span_lint_and_help(
cx,
SAME_ITEM_PUSH,

13
tests/ui/same_item_push.rs
View file

@ -1,5 +1,7 @@
#![warn(clippy::same_item_push)]
const VALUE: u8 = 7;
fn mutate_increment(x: &mut u8) -> u8 {
*x += 1;
*x
@ -111,4 +113,15 @@ fn main() {
for _ in 0..10 {
vec15.push(Box::new(S {}));
}
let mut vec16 = Vec::new();
for _ in 0..20 {
vec16.push(VALUE);
}
let mut vec17 = Vec::new();
let item = VALUE;
for _ in 0..20 {
vec17.push(item);
}
}

34
tests/ui/same_item_push.stderr
View file

@ -1,22 +1,14 @@
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:16:9
|
LL | spaces.push(vec![b' ']);
| ^^^^^^
|
= note: `-D clippy::same-item-push` implied by `-D warnings`
= help: try using vec![vec![b' '];SIZE] or spaces.resize(NEW_SIZE, vec![b' '])
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:22:9
--> $DIR/same_item_push.rs:24:9
|
LL | vec2.push(item);
| ^^^^
|
= note: `-D clippy::same-item-push` implied by `-D warnings`
= help: try using vec![item;SIZE] or vec2.resize(NEW_SIZE, item)
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:28:9
--> $DIR/same_item_push.rs:30:9
|
LL | vec3.push(item);
| ^^^^
@ -24,12 +16,28 @@ LL | vec3.push(item);
= help: try using vec![item;SIZE] or vec3.resize(NEW_SIZE, item)
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:33:9
--> $DIR/same_item_push.rs:35:9
|
LL | vec4.push(13);
| ^^^^
|
= help: try using vec![13;SIZE] or vec4.resize(NEW_SIZE, 13)
error: aborting due to 4 previous errors
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:119:9
|
LL | vec16.push(VALUE);
| ^^^^^
|
= help: try using vec![VALUE;SIZE] or vec16.resize(NEW_SIZE, VALUE)
error: it looks like the same item is being pushed into this Vec
--> $DIR/same_item_push.rs:125:9
|
LL | vec17.push(item);
| ^^^^^
|
= help: try using vec![item;SIZE] or vec17.resize(NEW_SIZE, item)
error: aborting due to 5 previous errors