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Rust compiler error · checked with rustc 1.99.0

Rust error E0571: `break` with value from a `while` loop

What it meansA break statement with an argument appeared in a non-loop loop.

What rustc prints

error[E0571]: `break` with value from a `while` loop
 --> main.rs:5:9
  |
3 | let result = while true {
  |              ---------- you can't `break` with a value in a `while` loop
4 |     if satisfied(i) {
5 |         break 2 * i; // error: `break` with value from a `while` loop
  |         ^^^^^^^^^^^ can only break with a value inside `loop` or breakable block
  |
help: use `break` on its own without a value inside this `while` loop
  |
5 -         break 2 * i; // error: `break` with value from a `while` loop
5 +         break; // error: `break` with value from a `while` loop
  |

Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.

E0571Everything else
Activein rustc 1.99.0
8related errors linked below

The compiler team's explanation

A break statement with an argument appeared in a non-loop loop.

Example of erroneous code:

let result = while true {
    if satisfied(i) {
        break 2 * i; // error: `break` with value from a `while` loop
    }
    i += 1;
};

The break statement can take an argument (which will be the value of the loop expression if the break statement is executed) in loop loops, but not for, while, or while let loops.

Make sure break value; statements only occur in loop loops:

let result = loop { // This is now a "loop" loop.
    if satisfied(i) {
        break 2 * i; // ok!
    }
    i += 1;
};

From rustc --explain E0571 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.

Related errors

All 518 Rust error codes · Rust crate data · Glossary

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