E0010: promise_violation

E0010 promise_violation — the cell breaks a promise of its face.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0010).

The rule

A structural promise in a cell's face (all_persistent, all_consistent, all_encrypted, has_memory, has_face, has_signals, has_auth) is checked against the cell's structure. promise all_persistent requires every memory slot to be marked [persistent]; one [ephemeral] slot breaks it. The message does not name the offending slot, so look at each slot's properties, then mark it [persistent] or remove the promise.

A program that triggers it

cell Ledger {
    face {
        promise all_persistent
        signal post(account: String, cents: Int) -> Int
    }
    memory {
        balances: Map<String, Int> [persistent, consistent]
        recent: Map<String, Int> [ephemeral]
    }
    on post(account: String, cents: Int) {
        let total = (balances.get(account) ?? 0) + cents
        balances.set(account, total)
        recent.set(account, cents)
        return total
    }
}

What soma check prints:

$ soma check wrong.cell
error: structural promise violated in cell 'Ledger': promise 'all_persistent' is not satisfied
  --> wrong.cell:3:17
  |
3 |         promise all_persistent
  |                 ^
  = code: E0010
✗ 1 error(s), 0 warning(s).

The fix field of soma check --json: Cell 'Ledger' violates promise 'all_persistent'. Either satisfy the constraint or remove the promise from the face section.

The fix

On line 8, recent: Map<String, Int> [ephemeral] becomes recent: Map<String, Int> [persistent].

--- wrong.cell
+++ right.cell
@@ -6,5 +6,5 @@
     memory {
         balances: Map<String, Int> [persistent, consistent]
-        recent: Map<String, Int> [ephemeral]
+        recent: Map<String, Int> [persistent]
     }
     on post(account: String, cents: Int) {

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.