Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::implicit_return: missing `return` statement

What it meansChecks for missing return statements at the end of a block. It is in the restriction group and off by default.

What you see

warning: missing `return` statement
 --> main.rs:4:5
  |
4 |     x
  |     ^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#implicit_return
  = note: requested on the command line with `-W clippy::implicit-return`
help: add `return` as shown
  |
4 |     return x
  |     ++++++

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?

Omitting the return keyword whenever possible is idiomatic Rust code, but: Programmers coming from other languages might prefer the expressiveness of return. It’s possible to miss the last returning statement because the only difference is a missing ;. Especially in bigger code with multiple return paths, having a return keyword makes it easier to find the corresponding statements.

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

fn foo(x: usize) -> usize {
    x
}

Write this instead

fn foo(x: usize) -> usize {
    return x;
}

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]
implicit_return = "warn"

In code

#![warn(clippy::implicit_return)]

One run

cargo clippy -- -W clippy::implicit-return

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.

Restrictiongroup

allowdefault level

yesfixed by cargo clippy --fix

1.33.0added in Rust

Clippy's own documentation

What it does

Checks for missing return statements at the end of a block.

Why restrict this?

Omitting the return keyword whenever possible is idiomatic Rust code, but:

Programmers coming from other languages might prefer the expressiveness of return.
It’s possible to miss the last returning statement because the only difference is a missing ;.
Especially in bigger code with multiple return paths, having a return keyword makes it easier to find the corresponding statements.

Example

fn foo(x: usize) -> usize {
    x
}

add return

fn foo(x: usize) -> usize {
    return x;
}

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

Up next

Also worth your time

Did this answer your question?