Missing return

Meaning

A function declares a return type, but at least one reachable control-flow path falls off the end.

Prismio requires explicit return expression; it does not use the final expression of a block as an implicit result. The check considers branches and terminating loops.

Why it happens

One if branch returns while the false path continues, a match lacks a fallback/return path, or a function's signature still promises a value after its body was changed to side effects only.

Invalid code

fn sign(value: Int) -> String {
    if (value > 0) { return "positive" }
}
fn main() -> Int { return 0 }

Correct code

import std.io

fn sign(value: Int) -> String {
    if (value > 0) { return "positive" }
    return "not positive"
}
fn main() -> Int {
    println(sign(1))
    return 0
}

Common fixes

Return in the remaining branch, add a final return, or remove the declared return type when no value should be produced.

The returned expression must exactly match the declared type. Do not add a dummy return merely to satisfy the compiler if the uncovered path represents a real application error; model that outcome explicitly since exceptions are not implemented.