acc3842d43
This lint checks for code that looks like
```rust
let something : Vec<_> = (0..100).map(|_| {
1 + 2 + 3
}).collect();
```
which is more clear as
```rust
let something : Vec<_> = std::iter::repeat_with(|| {
1 + 2 + 3
}).take(100).collect();
```
or
```rust
let something : Vec<_> =
std::iter::repeat_n(1 + 2 + 3, 100)
.collect();
```
That is, a map over a range which does nothing with the parameter
passed to it is simply a function (or closure) being called `n`
times and could be more semantically expressed using `take`.
36 lines
875 B
Rust
36 lines
875 B
Rust
#![allow(clippy::map_with_unused_argument_over_ranges)]
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#![warn(clippy::suspicious_map)]
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fn main() {
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let _ = (0..3).map(|x| x + 2).count();
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//~^ ERROR: this call to `map()` won't have an effect on the call to `count()`
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let f = |x| x + 1;
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let _ = (0..3).map(f).count();
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//~^ ERROR: this call to `map()` won't have an effect on the call to `count()`
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}
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fn negative() {
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// closure with side effects
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let mut sum = 0;
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let _ = (0..3).map(|x| sum += x).count();
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// closure variable with side effects
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let ext_closure = |x| sum += x;
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let _ = (0..3).map(ext_closure).count();
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// closure that returns unit
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let _ = (0..3)
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.map(|x| {
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// do nothing
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})
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.count();
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// external function
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let _ = (0..3).map(do_something).count();
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}
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fn do_something<T>(t: T) -> String {
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unimplemented!()
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}
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