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Auto merge of #11862 - christophbeberweil:7125-single-element-loop-over-range, r=llogiq

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suggest alternatives to iterate an array of ranges

works towards #7125
changelog: [`single_element_loop`]: suggest better syntax when iterating over an array of a single range

`@thinkerdreamer` and myself worked on this issue during a workshop by `@llogiq` at the RustLab 2023 conference. It is our first contribution to clippy.

When iterating over an array of only one element, _which is a range_, our change suggests to replace the array with the contained range itself. Additionally, a hint is printed stating that the user probably intended to iterate over the range and not the array. If the single element in the array is not a range, the previous suggestion in the form of `let {pat_snip} = {prefix}{arg_snip};{block_str}`is used.

This change lints the array with the single range directly, so any prefixes or suffixes are covered as well.
This commit is contained in:
bors 2023-11-24 17:15:33 +00:00
commit 6cfbe57075
3 changed files with 45 additions and 74 deletions
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35
clippy_lints/src/loops/single_element_loop.rs
View File

@ -1,6 +1,6 @@
use super::SINGLE_ELEMENT_LOOP;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, snippet_with_applicability};
use clippy_utils::source::{indent_of, snippet, snippet_with_applicability};
use clippy_utils::visitors::contains_break_or_continue;
use rustc_ast::util::parser::PREC_PREFIX;
use rustc_ast::Mutability;
@ -87,14 +87,29 @@ pub(super) fn check<'tcx>(
arg_snip = format!("({arg_snip})").into();
}
span_lint_and_sugg(
cx,
SINGLE_ELEMENT_LOOP,
expr.span,
"for loop over a single element",
"try",
format!("{{\n{indent}let {pat_snip} = {prefix}{arg_snip};{block_str}}}"),
applicability,
);
if clippy_utils::higher::Range::hir(arg_expression).is_some() {
let range_expr = snippet(cx, arg_expression.span, "?").to_string();
let sugg = snippet(cx, arg_expression.span, "..");
span_lint_and_sugg(
cx,
SINGLE_ELEMENT_LOOP,
arg.span,
format!("this loops only once with `{pat_snip}` being `{range_expr}`").as_str(),
"did you mean to iterate over the range instead?",
sugg.to_string(),
Applicability::Unspecified,
);
} else {
span_lint_and_sugg(
cx,
SINGLE_ELEMENT_LOOP,
expr.span,
"for loop over a single element",
"try",
format!("{{\n{indent}let {pat_snip} = {prefix}{arg_snip};{block_str}}}"),
applicability,
);
}
}
}

12
tests/ui/single_element_loop.fixed
View File

@ -15,23 +15,19 @@ fn main() {
dbg!(item);
}
{
let item = &(0..5);
for item in 0..5 {
dbg!(item);
}
{
let item = &mut (0..5);
for item in 0..5 {
dbg!(item);
}
{
let item = 0..5;
for item in 0..5 {
dbg!(item);
}
{
let item = 0..5;
for item in 0..5 {
dbg!(item);
}

72
tests/ui/single_element_loop.stderr
View File

@ -32,69 +32,29 @@ LL + dbg!(item);
LL + }
|
error: for loop over a single element
--> $DIR/single_element_loop.rs:16:5
|
LL | / for item in &[0..5] {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = &(0..5);
LL + dbg!(item);
LL + }
error: this loops only once with `item` being `0..5`
--> $DIR/single_element_loop.rs:16:17
|
LL | for item in &[0..5] {
| ^^^^^^^ help: did you mean to iterate over the range instead?: `0..5`
error: for loop over a single element
--> $DIR/single_element_loop.rs:20:5
|
LL | / for item in [0..5].iter_mut() {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = &mut (0..5);
LL + dbg!(item);
LL + }
error: this loops only once with `item` being `0..5`
--> $DIR/single_element_loop.rs:20:17
|
LL | for item in [0..5].iter_mut() {
| ^^^^^^^^^^^^^^^^^ help: did you mean to iterate over the range instead?: `0..5`
error: for loop over a single element
--> $DIR/single_element_loop.rs:24:5
|
LL | / for item in [0..5] {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = 0..5;
LL + dbg!(item);
LL + }
error: this loops only once with `item` being `0..5`
--> $DIR/single_element_loop.rs:24:17
|
LL | for item in [0..5] {
| ^^^^^^ help: did you mean to iterate over the range instead?: `0..5`
error: for loop over a single element
--> $DIR/single_element_loop.rs:28:5
|
LL | / for item in [0..5].into_iter() {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = 0..5;
LL + dbg!(item);
LL + }
error: this loops only once with `item` being `0..5`
--> $DIR/single_element_loop.rs:28:17
|
LL | for item in [0..5].into_iter() {
| ^^^^^^^^^^^^^^^^^^ help: did you mean to iterate over the range instead?: `0..5`
error: for loop over a single element
--> $DIR/single_element_loop.rs:47:5