021 field punning shorthand

// Test 210_021: Struct Field Punning Shorthand
// When field value is an expression like `p.x`, infer field name from last segment
//
// Syntax: { p.x, p.y } should expand to { x: p.x, y: p.y }

~import std/io

pub const Point = struct { x: i32, y: i32 };

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

~proc make-point|zig {
    return .{ .point = Point{ .x = x, .y = y } };
}

~event use-point { p: Point }
| result { x: i32, y: i32 }

// Shorthand: { p.x, p.y } should become { x: p.x, y: p.y }
~use-point => result { p.x, p.y }

// Test it
~make-point(x: 10, y: 20)
| point pt |> use-point(p: pt)
    | result r |> std/io:print.ln("punning works: x={{ r.x:d }}, y={{ r.y:d }}")