132 comptime walk branch residue

// A walked comptime subflow's RESULT dispatches the residue's branch arms.
// `route` walks pick, re-produces its branch through `=>` arm tails, and the
// residue's `| small v` arm matches — its continuation chain (the print) is
// promoted while the non-matching `| big` arm emits nothing.
~import std/io

~[comptime] tor pick { n: i64 }
| small i64
| big i64
~proc pick|zig {
    if (n < 10) return .{ .small = n };
    return .{ .big = n };
}

~[comptime] tor route { n: i64 }
| small i64
| big i64
~route = pick(n)
| small v => small v
| big v => big v

~route(n: 4)
| small v |> std/io:print.ln("small {{ v:d }}")
| big v |> std/io:print.ln("big {{ v:d }}")