Closed
Description
The find_map lint will trigger if you do a filter followed by a map but its not always preferable.
---- dogfood stdout ----
status: exit code: 101
stdout:
stderr: Blocking waiting for file lock on package cache lock
Checking clippy v0.0.212 (/home/jlusby/git/rust/clippy)
error: called `find(p).map(q)` on an `Iterator`. This is more succinctly expressed by calling `.find_map(..)` instead.
--> src/driver.rs:129:9
|
129 | / LINT_LEVELS
130 | | .iter()
131 | | .find(|level_mapping| level_mapping.0 == lint.group)
132 | | .map(|(_, level)| level)
| |____________________________________^
|
= note: `-D clippy::find-map` implied by `-D clippy::pedantic`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#find_map
error: called `filter(p).map(q)` on an `Iterator`. This is more succinctly expressed by calling `.filter_map(..)` instead.
--> src/driver.rs:205:24
|
205 | let desc = lints
| ________________________^
206 | | .iter()
207 | | .filter(|&lint| lint.group == group)
208 | | .map(|lint| lint.name)
| |______________________________________^
|
= note: `-D clippy::filter-map` implied by `-D clippy::pedantic`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#filter_map
error: called `find(p).map(q)` on an `Iterator`. This is more succinctly expressed by calling `.find_map(..)` instead.
--> src/driver.rs:129:9
|
129 | / LINT_LEVELS
130 | | .iter()
131 | | .find(|level_mapping| level_mapping.0 == lint.group)
132 | | .map(|(_, level)| level)
| |____________________________________^
|
= note: `-D clippy::find-map` implied by `-D clippy::pedantic`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#find_map
error: called `filter(p).map(q)` on an `Iterator`. This is more succinctly expressed by calling `.filter_map(..)` instead.
--> src/driver.rs:205:24
|
205 | let desc = lints
| ________________________^
206 | | .iter()
207 | | .filter(|&lint| lint.group == group)
208 | | .map(|lint| lint.name)
| |______________________________________^
|
= note: `-D clippy::filter-map` implied by `-D clippy::pedantic`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#filter_map
error: aborting due to 2 previous errors
In the case of the first lint at least, you'll run into lifetime issues if you try to replace lines 131 and 132 with a find_map call.
LINT_LEVELS
.iter()
.find_map(|level_mapping| {
if level_mapping.0 == lint.group {
Some(level_mapping.1)
} else {
None
}
})
.map(|level| match level {
Level::Allow => "allow",
Level::Warn => "warn",
Level::Deny => "deny",
})
.unwrap()master ✗ $ cargo check
Checking clippy v0.0.212 (/home/jlusby/git/rust/clippy)
error[E0507]: cannot move out of `level_mapping.1` which is behind a shared reference
--> src/driver.rs:133:26
|
133 | Some(level_mapping.1)
| ^^^^^^^^^^^^^^^ move occurs because `level_mapping.1` has type `lintlist::lint::Level`, which does not implement the `Copy` trait
error: aborting due to previous error
For more information about this error, try `rustc --explain E0507`.
error: Could not compile `clippy`.
To learn more, run the command again with --verbose.
And even if it didn't run into the borrow error I personally feel like the find_map version is less concise than the filter -> map version.
If the Item type of the iterator was already a Try type then I can see it being easy enough to write a concise find_map impl, but with the boolean as the only starting point for the closure outputting Some or None I don't think it works as nicely as filter and map.