RS.CLIPPY.FILTER_MAP_BOOL_THEN
Checks for usage of `bool::then` in `Iterator::filter_map`
This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: filter_map_bool_then. Copyright ©2025 The Rust Team. All rights reserved.
What it does
Checks for usage of bool::then in Iterator::filter_map.
Why is this bad?
This can be written with filter then map instead, which would reduce nesting and
separates the filtering from the transformation phase. This comes with no cost to
performance and is just cleaner.
Limitations
Does not lint bool::then_some, as it eagerly evaluates its arguments rather than lazily.
This can create differing behavior, so better safe than sorry.
Example
_ = v.into_iter().filter_map(|i| (i % 2 == 0).then(|| really_expensive_fn(i)));
Use instead:
_ = v.into_iter().filter(|i| i % 2 == 0).map(|i| really_expensive_fn(i));