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Improve slow_vector_initialization suggestion (#13912)

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close #13781

The `slow_vector_initialization` lint currently only suggests using the
`vec!` macro with size, but it does not suggest removing the `resize`
method call.

changelog: [`slow_vector_initialization`]: improve
`slow_vector_initialization` suggestion
This commit is contained in:
Alejandra González 2025-01-01 19:21:01 +00:00 • committed by GitHub
commit 034f3d224c
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GPG key ID: B5690EEEBB952194
3 changed files with 104 additions and 87 deletions
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22
clippy_lints/src/slow_vector_initialization.rs
View file

@ -1,4 +1,4 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::macros::matching_root_macro_call;
use clippy_utils::sugg::Sugg;
use clippy_utils::{
@ -203,14 +203,18 @@ impl SlowVectorInit {
"len",
);
span_lint_and_then(cx, SLOW_VECTOR_INITIALIZATION, slow_fill.span, msg, |diag| {
diag.span_suggestion(
vec_alloc.allocation_expr.span.source_callsite(),
"consider replacing this with",
format!("vec![0; {len_expr}]"),
Applicability::Unspecified,
);
});
let span_to_replace = slow_fill
.span
.with_lo(vec_alloc.allocation_expr.span.source_callsite().lo());
span_lint_and_sugg(
cx,
SLOW_VECTOR_INITIALIZATION,
span_to_replace,
msg,
"consider replacing this with",
format!("vec![0; {len_expr}]"),
Applicability::Unspecified,
);
}
}

26
tests/ui/slow_vector_initialization.rs
View file

@ -11,22 +11,22 @@ fn extend_vector() {
// Extend with constant expression
let len = 300;
let mut vec1 = Vec::with_capacity(len);
vec1.extend(repeat(0).take(len));
//~^ ERROR: slow zero-filling initialization
//~| NOTE: `-D clippy::slow-vector-initialization` implied by `-D warnings`
vec1.extend(repeat(0).take(len));
// Extend with len expression
let mut vec2 = Vec::with_capacity(len - 10);
vec2.extend(repeat(0).take(len - 10));
//~^ ERROR: slow zero-filling initialization
vec2.extend(repeat(0).take(len - 10));
// Extend with mismatching expression should not be warned
let mut vec3 = Vec::with_capacity(24322);
vec3.extend(repeat(0).take(2));
let mut vec4 = Vec::with_capacity(len);
vec4.extend(repeat(0).take(vec4.capacity()));
//~^ ERROR: slow zero-filling initialization
vec4.extend(repeat(0).take(vec4.capacity()));
}
fn mixed_extend_resize_vector() {
@ -36,20 +36,20 @@ fn mixed_extend_resize_vector() {
// Slow initialization
let mut resized_vec = Vec::with_capacity(30);
resized_vec.resize(30, 0);
//~^ ERROR: slow zero-filling initialization
resized_vec.resize(30, 0);
let mut extend_vec = Vec::with_capacity(30);
extend_vec.extend(repeat(0).take(30));
//~^ ERROR: slow zero-filling initialization
extend_vec.extend(repeat(0).take(30));
}
fn resize_vector() {
// Resize with constant expression
let len = 300;
let mut vec1 = Vec::with_capacity(len);
vec1.resize(len, 0);
//~^ ERROR: slow zero-filling initialization
vec1.resize(len, 0);
// Resize mismatch len
let mut vec2 = Vec::with_capacity(200);
@ -57,39 +57,39 @@ fn resize_vector() {
// Resize with len expression
let mut vec3 = Vec::with_capacity(len - 10);
vec3.resize(len - 10, 0);
//~^ ERROR: slow zero-filling initialization
vec3.resize(len - 10, 0);
let mut vec4 = Vec::with_capacity(len);
vec4.resize(vec4.capacity(), 0);
//~^ ERROR: slow zero-filling initialization
vec4.resize(vec4.capacity(), 0);
// Reinitialization should be warned
vec1 = Vec::with_capacity(10);
vec1.resize(10, 0);
//~^ ERROR: slow zero-filling initialization
vec1.resize(10, 0);
}
fn from_empty_vec() {
// Resize with constant expression
let len = 300;
let mut vec1 = Vec::new();
vec1.resize(len, 0);
//~^ ERROR: slow zero-filling initialization
vec1.resize(len, 0);
// Resize with len expression
let mut vec3 = Vec::new();
vec3.resize(len - 10, 0);
//~^ ERROR: slow zero-filling initialization
vec3.resize(len - 10, 0);
// Reinitialization should be warned
vec1 = Vec::new();
vec1.resize(10, 0);
//~^ ERROR: slow zero-filling initialization
vec1.resize(10, 0);
vec1 = vec![];
vec1.resize(10, 0);
//~^ ERROR: slow zero-filling initialization
vec1.resize(10, 0);
macro_rules! x {
() => {

143
tests/ui/slow_vector_initialization.stderr
View file

@ -1,109 +1,122 @@
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:14:5
--> tests/ui/slow_vector_initialization.rs:13:20
|
LL | let mut vec1 = Vec::with_capacity(len);
| ----------------------- help: consider replacing this with: `vec![0; len]`
LL | vec1.extend(repeat(0).take(len));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec1 = Vec::with_capacity(len);
| ____________________^
... |
LL | | vec1.extend(repeat(0).take(len));
| |____________________________________^ help: consider replacing this with: `vec![0; len]`
|
= note: `-D clippy::slow-vector-initialization` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::slow_vector_initialization)]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:20:5
--> tests/ui/slow_vector_initialization.rs:19:20
|
LL | let mut vec2 = Vec::with_capacity(len - 10);
| ---------------------------- help: consider replacing this with: `vec![0; len - 10]`
LL | vec2.extend(repeat(0).take(len - 10));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec2 = Vec::with_capacity(len - 10);
| ____________________^
LL | |
LL | | vec2.extend(repeat(0).take(len - 10));
| |_________________________________________^ help: consider replacing this with: `vec![0; len - 10]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:28:5
--> tests/ui/slow_vector_initialization.rs:27:20
|
LL | let mut vec4 = Vec::with_capacity(len);
| ----------------------- help: consider replacing this with: `vec![0; len]`
LL | vec4.extend(repeat(0).take(vec4.capacity()));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec4 = Vec::with_capacity(len);
| ____________________^
LL | |
LL | | vec4.extend(repeat(0).take(vec4.capacity()));
| |________________________________________________^ help: consider replacing this with: `vec![0; len]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:39:5
--> tests/ui/slow_vector_initialization.rs:38:27
|
LL | let mut resized_vec = Vec::with_capacity(30);
| ---------------------- help: consider replacing this with: `vec![0; 30]`
LL | resized_vec.resize(30, 0);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut resized_vec = Vec::with_capacity(30);
| ___________________________^
LL | |
LL | | resized_vec.resize(30, 0);
| |_____________________________^ help: consider replacing this with: `vec![0; 30]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:43:5
--> tests/ui/slow_vector_initialization.rs:42:26
|
LL | let mut extend_vec = Vec::with_capacity(30);
| ---------------------- help: consider replacing this with: `vec![0; 30]`
LL | extend_vec.extend(repeat(0).take(30));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut extend_vec = Vec::with_capacity(30);
| __________________________^
LL | |
LL | | extend_vec.extend(repeat(0).take(30));
| |_________________________________________^ help: consider replacing this with: `vec![0; 30]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:51:5
--> tests/ui/slow_vector_initialization.rs:50:20
|
LL | let mut vec1 = Vec::with_capacity(len);
| ----------------------- help: consider replacing this with: `vec![0; len]`
LL | vec1.resize(len, 0);
| ^^^^^^^^^^^^^^^^^^^
LL | let mut vec1 = Vec::with_capacity(len);
| ____________________^
LL | |
LL | | vec1.resize(len, 0);
| |_______________________^ help: consider replacing this with: `vec![0; len]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:60:5
--> tests/ui/slow_vector_initialization.rs:59:20
|
LL | let mut vec3 = Vec::with_capacity(len - 10);
| ---------------------------- help: consider replacing this with: `vec![0; len - 10]`
LL | vec3.resize(len - 10, 0);
| ^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec3 = Vec::with_capacity(len - 10);
| ____________________^
LL | |
LL | | vec3.resize(len - 10, 0);
| |____________________________^ help: consider replacing this with: `vec![0; len - 10]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:64:5
--> tests/ui/slow_vector_initialization.rs:63:20
|
LL | let mut vec4 = Vec::with_capacity(len);
| ----------------------- help: consider replacing this with: `vec![0; len]`
LL | vec4.resize(vec4.capacity(), 0);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec4 = Vec::with_capacity(len);
| ____________________^
LL | |
LL | | vec4.resize(vec4.capacity(), 0);
| |___________________________________^ help: consider replacing this with: `vec![0; len]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:69:5
--> tests/ui/slow_vector_initialization.rs:68:12
|
LL | vec1 = Vec::with_capacity(10);
| ---------------------- help: consider replacing this with: `vec![0; 10]`
LL | vec1.resize(10, 0);
| ^^^^^^^^^^^^^^^^^^
LL | vec1 = Vec::with_capacity(10);
| ____________^
LL | |
LL | | vec1.resize(10, 0);
| |______________________^ help: consider replacing this with: `vec![0; 10]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:77:5
--> tests/ui/slow_vector_initialization.rs:76:20
|
LL | let mut vec1 = Vec::new();
| ---------- help: consider replacing this with: `vec![0; len]`
LL | vec1.resize(len, 0);
| ^^^^^^^^^^^^^^^^^^^
LL | let mut vec1 = Vec::new();
| ____________________^
LL | |
LL | | vec1.resize(len, 0);
| |_______________________^ help: consider replacing this with: `vec![0; len]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:82:5
--> tests/ui/slow_vector_initialization.rs:81:20
|
LL | let mut vec3 = Vec::new();
| ---------- help: consider replacing this with: `vec![0; len - 10]`
LL | vec3.resize(len - 10, 0);
| ^^^^^^^^^^^^^^^^^^^^^^^^
LL | let mut vec3 = Vec::new();
| ____________________^
LL | |
LL | | vec3.resize(len - 10, 0);
| |____________________________^ help: consider replacing this with: `vec![0; len - 10]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:87:5
--> tests/ui/slow_vector_initialization.rs:86:12
|
LL | vec1 = Vec::new();
| ---------- help: consider replacing this with: `vec![0; 10]`
LL | vec1.resize(10, 0);
| ^^^^^^^^^^^^^^^^^^
LL | vec1 = Vec::new();
| ____________^
LL | |
LL | | vec1.resize(10, 0);
| |______________________^ help: consider replacing this with: `vec![0; 10]`
error: slow zero-filling initialization
--> tests/ui/slow_vector_initialization.rs:91:5
--> tests/ui/slow_vector_initialization.rs:90:12
|
LL | vec1 = vec![];
| ------ help: consider replacing this with: `vec![0; 10]`
LL | vec1.resize(10, 0);
| ^^^^^^^^^^^^^^^^^^
LL | vec1 = vec![];
| ____________^
LL | |
LL | | vec1.resize(10, 0);
| |______________________^ help: consider replacing this with: `vec![0; 10]`
error: aborting due to 13 previous errors