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suggest alternatives to iterate an array of ranges #11862

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merged 5 commits into from
Nov 24, 2023
Merged

suggest alternatives to iterate an array of ranges #11862

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447edf9
suggest alternatives to iterate an array of ranges
christophbeberweil Nov 23, 2023
c58d692
fix: 7125 update lint applicability to Unspecified
christophbeberweil Nov 24, 2023
2512341
feat: 7125 shorten lint text
christophbeberweil Nov 24, 2023
bce869f
fix: 7125 lint message should start with a small letter
christophbeberweil Nov 24, 2023
f9c6335
feat: 7125 code snippets are wrapped in backticks
christophbeberweil Nov 24, 2023
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33 changes: 23 additions & 10 deletions clippy_lints/src/loops/single_element_loop.rs
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Original file line number Diff line number Diff line change
@@ -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;
Expand Down Expand Up @@ -87,14 +87,27 @@ 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 sugg = snippet(cx, arg_expression.span, "..");
span_lint_and_sugg(
cx,
SINGLE_ELEMENT_LOOP,
arg.span,
"for loop over a single range inside an array, rather than iterating over the elements in the range directly",
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@llogiq llogiq Nov 24, 2023 •
edited

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Perhaps we can find a shorter way to phrase this? I like the clarity though. Maybe something like "This loops only once with <loop pattern> being <range expr>", which is admittedly harder to construct.

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We discussed a lot about the message of this lint, but opted for a longer and more verbose one. I adjusted it to contain your version, which is shorter, but now the text "0..5" is written twice in the lint message, which feels redundant to me.

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I see it as "item" (the looping variable name) and "0..5", rather than 0..5 twice. Am I missing something?

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This is the current output of the lint:

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`

"0-5" is mentioned in the lint error message and in the suggestion. I thing mentioning it once should be enough, but mentioning it twice will probably not hurt.

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... and with a lowercase "t" the error message actually passes the tests, which were failing with my commit from earlier today. :)

"did you mean to iterate over the range instead?",
sugg.to_string(),
applicability,
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Suggested change
applicability,
Applicability::Unspecified,

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Done

);
} 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 changes: 4 additions & 8 deletions tests/ui/single_element_loop.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand Down
72 changes: 16 additions & 56 deletions tests/ui/single_element_loop.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -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: for loop over a single range inside an array, rather than iterating over the elements in the range directly
--> $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: for loop over a single range inside an array, rather than iterating over the elements in the range directly
--> $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: for loop over a single range inside an array, rather than iterating over the elements in the range directly
--> $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: for loop over a single range inside an array, rather than iterating over the elements in the range directly
--> $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
Expand Down