clippy::needless_continue: The lint checks for if-statements appearing in loops that contain a continue statement in either their main blocks or their else-blocks, when omitting the else-block possibly with some rearrangement of code can make the code easier to understand. The lint also checks if the last statement in the loop is a continue

while condition() {
    update_condition();
    if x {
        // ...
    } else {
        continue;
    }
    println!("Hello, world");
}

while condition() {
    update_condition();
    if x {
        // ...
        println!("Hello, world");
    }
}

[lints.clippy]
needless_continue = "warn"

#![warn(clippy::needless_continue)]

cargo clippy -- -W clippy::needless-continue

Clippy's own documentation

What it does

The lint checks for if-statements appearing in loops that contain a continue statement in either their main blocks or their else-blocks, when omitting the else-block possibly with some rearrangement of code can make the code easier to understand. The lint also checks if the last statement in the loop is a continue

Why is this bad?

Having explicit else blocks for if statements containing continue in their THEN branch adds unnecessary branching and nesting to the code. Having an else block containing just continue can also be better written by grouping the statements following the whole if statement within the THEN block and omitting the else block completely.

Example

while condition() {
    update_condition();
    if x {
        // ...
    } else {
        continue;
    }
    println!("Hello, world");
}

Could be rewritten as

while condition() {
    update_condition();
    if x {
        // ...
        println!("Hello, world");
    }
}

As another example, the following code

loop {
    if waiting() {
        continue;
    } else {
        // Do something useful
    }
    # break;
}

Could be rewritten as

loop {
    if waiting() {
        continue;
    }
    // Do something useful
    # break;
}

fn foo() -> ErrorKind { ErrorKind::NotFound }
for _ in 0..10 {
    match foo() {
        ErrorKind::NotFound => {
            eprintln!("not found");
            continue
        }
        ErrorKind::TimedOut => {
            eprintln!("timeout");
            continue
        }
        _ => {
            eprintln!("other error");
            continue
        }
    }
}

Could be rewritten as

fn foo() -> ErrorKind { ErrorKind::NotFound }
for _ in 0..10 {
    match foo() {
        ErrorKind::NotFound => {
            eprintln!("not found");
        }
        ErrorKind::TimedOut => {
            eprintln!("timeout");
        }
        _ => {
            eprintln!("other error");
        }
    }
}

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

Related lints

• too_many_linesChecks for functions with a large amount of lines
• missing_errors_docChecks the doc comments of publicly visible functions that return a Result type and warns if there is no # Errors section
• must_use_candidateChecks for public functions that have no #[must_use] attribute, but return something not already marked must-use, have no mutable arg and mutate no statics
• mut_mutmultiple successive mutable borrows
• naive_bytecountChecks for naive byte counts
• needless_bitwise_booluse of bitwise operator instead of lazy operator between booleans
• needless_for_eachneedless use of `for_each`
• needless_pass_by_valuethis argument is passed by value, but not consumed in the function body
• needless_raw_string_hashesunnecessary hashes around raw string literal

All 847 Clippy lints · Rust compiler errors · Cargo.toml checker