E0073: pipe_right_side

E0073 pipe_right_side — the right side of |> is not a call.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0073).

The rule

The right side of |> must be a call: x |> f(a) means f(x, a). In prices |> sum() * 1.2 the right side is the product sum() * 1.2, not a call, so check refuses it (and also reports sum() called with no argument). Parenthesise the pipe before combining its result: (prices |> sum()) * 1.2.

A program that triggers it

cell Invoice {
    on total_with_tax(prices: List<Float>) {
        let total = prices |> sum() * 1.2
        return total
    }
}

What soma check prints:

$ soma check wrong.cell
error: the right side of `|>` must be a call — `x |> f(a)` means f(x, a); to combine the result, parenthesise: `(x |> f()) + 1`
  --> wrong.cell:3:31
  |
3 |         let total = prices |> sum() * 1.2
  |                               ^
  = code: E0073
error: sum() needs at least 1 argument (0 given) — sum(list: List) -> Int|Float
  --> wrong.cell:3:31
  |
3 |         let total = prices |> sum() * 1.2
  |                               ^
  = code: E0101
✗ 2 error(s), 0 warning(s).

The fix field of soma check --json: `x |> f(a)` means f(x, a); to combine the result, parenthesise: `(x |> f()) + 1`

The fix

On line 3, let total = prices |> sum() * 1.2 becomes let total = (prices |> sum()) * 1.2.

--- wrong.cell
+++ right.cell
@@ -1,5 +1,5 @@
 cell Invoice {
     on total_with_tax(prices: List<Float>) {
-        let total = prices |> sum() * 1.2
+        let total = (prices |> sum()) * 1.2
         return total
     }

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.