Clippy lint · Pedantic · checked with Clippy 0.1.99

clippy::iter_filter_is_some: `filter` for `is_some` on iterator over `Option`

What it meansChecks for usage of .filter(Option::is_some) that may be replaced with a .flatten() call. This lint will require additional changes to the follow-up calls as it affects the type. It is in the pedantic group and off by default.

What you see

warning: `filter` for `is_some` on iterator over `Option`
 --> main.rs:3:27
  |
3 | vec![Some(1)].into_iter().filter(Option::is_some);
  |                           ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `flatten` instead: `flatten()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#iter_filter_is_some
  = note: `-W clippy::iter-filter-is-some` implied by `-W clippy::pedantic`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

This pattern is often followed by manual unwrapping of the Option. The simplification results in more readable and succinct code without the need for manual unwrapping.

Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

vec![Some(1)].into_iter().filter(Option::is_some);

Write this instead

vec![Some(1)].into_iter().flatten();

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
iter_filter_is_some = "warn"

In code

#![warn(clippy::iter_filter_is_some)]

One run

cargo clippy -- -W clippy::iter-filter-is-some

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Pedanticgroup

allowdefault level

nofixed by cargo clippy --fix

1.77.0added in Rust

Clippy's own documentation

What it does

Checks for usage of .filter(Option::is_some) that may be replaced with a .flatten() call. This lint will require additional changes to the follow-up calls as it affects the type.

Why is this bad?

This pattern is often followed by manual unwrapping of the Option. The simplification results in more readable and succinct code without the need for manual unwrapping.

Example

vec![Some(1)].into_iter().filter(Option::is_some);

Use instead:

vec![Some(1)].into_iter().flatten();

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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