E0103: break_outside_loop

E0103 break_outside_loop — break / continue outside a loop.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0103).

The rule

break and continue only mean something inside a for or while loop, and soma check reports E0103 anywhere else, here in match arms written like the cases of a C switch. A Soma match runs exactly one arm and never falls through to the next, so the arm needs no break. Delete it; to leave a handler early, use return.

A program that triggers it

cell Billing {
    face {
        signal late_fee(status: String, days_late: Int) -> Int
    }
    on late_fee(status: String, days_late: Int) {
        let fee = 0
        match status {
            "paid" -> {
                fee = 0
                break
            }
            "overdue" -> {
                fee = 500 + days_late * 25
                break
            }
            _ -> { fee = 0 }
        }
        return fee
    }
}

What soma check prints:

$ soma check wrong.cell
error: `break` outside a loop — it only means something inside `for` / `while` (to leave a handler, `return`)
  --> wrong.cell:10:17
   |
10 |                 break
   |                 ^
  = code: E0103
error: `break` outside a loop — it only means something inside `for` / `while` (to leave a handler, `return`)
  --> wrong.cell:14:17
   |
14 |                 break
   |                 ^
  = code: E0103
✗ 2 error(s), 0 warning(s).

The fix field of soma check --json: it only means something inside `for` / `while` (to leave a handler, `return`)

The fix

Line 10 is removed; line 14 is removed.

--- wrong.cell
+++ right.cell
@@ -8,9 +8,7 @@
             "paid" -> {
                 fee = 0
-                break
             }
             "overdue" -> {
                 fee = 500 + days_late * 25
-                break
             }
             _ -> { fee = 0 }

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.