E0084: interpolation_trailing

E0084 interpolation_trailing — text after the expression of an interpolation.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0084).

The rule

An interpolation {...} must hold exactly one expression. In {total - fee cents} the word cents is a second expression, and the message says that part would be dropped. Close the brace after the expression and keep the text outside it, or bind the value with a let first.

A program that triggers it

cell Receipt {
    on summary(customer: String, total: Int, fee: Int) {
        return "{customer} owes {total - fee cents}"
    }
}

What soma check prints:

$ soma check wrong.cell
error: string interpolation `{total - fee cents}` is not one expression — the part after it would be dropped; bind it with a let first
  --> wrong.cell:3:16
  |
3 |         return "{customer} owes {total - fee cents}"
  |                ^
  = code: E0084
✗ 1 error(s), 0 warning(s).

The fix field of soma check --json: the part after it would be dropped; bind it with a let first

The fix

On line 3, return "{customer} owes {total - fee cents}" becomes return "{customer} owes {total - fee} cents".

--- wrong.cell
+++ right.cell
@@ -1,5 +1,5 @@
 cell Receipt {
     on summary(customer: String, total: Int, fee: Int) {
-        return "{customer} owes {total - fee cents}"
+        return "{customer} owes {total - fee} cents"
     }
 }

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.