E0012: dispatch

E0012 dispatch — a call resolves to no handler, to several, or with the wrong argument count.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0012).

The rule

A bare call must resolve to exactly one handler with that argument count. When two cells define pack, a third cell's pack(id) is ambiguous, and soma check asks you to qualify it rather than pick one silently. Write Warehouse.pack(id) (or rename one handler); the same code covers a call to a handler with the wrong number of arguments and a call to a name nothing defines.

A program that triggers it

cell Orders {
    memory {
        packed: Map<String, Bool> [persistent]
    }
    on pack(id: String) {
        packed.set(id, true)
    }
}

cell Warehouse {
    memory {
        shelves: Map<String, String> [persistent]
    }
    on pack(id: String) {
        shelves.set(id, "packing")
    }
}

cell Shipping {
    on ship(id: String) {
        pack(id)
        return "shipped {id}"
    }
}

What soma check prints:

$ soma check wrong.cell
error: ambiguous call 'pack': defined by cells Orders and Warehouse — qualify it (`Orders.pack(…)`) or rename one handler
  --> wrong.cell:21:9
   |
21 |         pack(id)
   |         ^
  = code: E0012
✗ 1 error(s), 0 warning(s).

The fix field of soma check --json: Define the missing handler, fix the spelling, or rename one of the colliding handlers so the call resolves to exactly one cell.

The fix

On line 21, pack(id) becomes Warehouse.pack(id).

--- wrong.cell
+++ right.cell
@@ -19,5 +19,5 @@
 cell Shipping {
     on ship(id: String) {
-        pack(id)
+        Warehouse.pack(id)
         return "shipped {id}"
     }

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.