Expression without a value

Built from the repository at commit a8614dc.

An expression whose value is used must have one. A call of a function that returns nothing has none, and neither has an if without an else. An expression that never finishes, such as an if whose branches all return, has none either. Nor has a bare break in a loop whose other breaks give it a value.

Why

A let, an argument, an operand or a condition needs a value to work with. Nothing is left to bind when the expression returns nothing, or never returns.

Broken

fn greet() {
    print(1)
}

fn main() {
    let x = greet()
    print(x)
}

What sisu says

error[E0043]: expression has no value
 --> E0043.sisu:6:13
  |
6 |     let x = greet()
  |             ^^^^^^^

sisu: 1 error
sisu: for more on a code, run `sisu explain <code>`: E0043

Fixed

fn one() -> i64 {
    1
}

fn main() {
    let x = one()
    print(x)
}

Related

• W0001: a statement that follows one that never finishes.