error: a many-pointer '[*]T' does not coerce to a slice '[]T' implicitly (it carries no length) — slice it with a length: ptr[0..len]
  --> examples/1183-diagnostics-many-pointer-to-slice-rejected.sx:21:10
   |
21 |     r := sum(xs.items);   // [*]i64 → []i64 — needs xs.items[0..xs.len]
   |          ^^^^^^^^^^^^^
