090 reject redundant punning constructor

// ============================================================================
// Test 210_090: MUST_FAIL — explicit field label `x: x` in a branch
//                          constructor is forbidden because punning would
//                          produce the same field name.
//
// Both `{ x: x }` and `{ x: p.x }` are rejected. The canonical forms are
// `{ x }` and `{ p.x }` respectively — the last segment names the field.
// ============================================================================

~import std/io

~event make-point { x: i32, y: i32 }
| point { x: i32, y: i32 }

// Explicit labels `x: x, y: y` are redundant — punning produces the same names.
~make-point => point { x: x, y: y }

~make-point(x: 10, y: 20)
| point p |> std/io:print.ln("x={{ p.x:d }}")