035 interpreter binding args

// Test: Interpreter binding reference evaluation in args
//
// This tests that when we chain events like:
//   ~first() | ok x |> second(arg: x.field)
//
// The interpreter evaluates x.field against the environment,
// NOT passing the literal string "x.field".

~import "$std/runtime"
~import "$std/interpreter"
~import "$std/io"

const std = @import("std");

// Event that produces a value
~pub event produce {}
| value { num: []const u8 }

~proc produce {
    return .{ .value = .{ .num = "42" } };
}

// Event that consumes a value and echoes it
~pub event consume { n: []const u8 }
| echoed { got: []const u8 }

~consume = std.io:print.ln("[consume] received n = '{{n:s}}'")
    |> echoed { got: n }

~std.runtime:register(scope: "test") {
    produce
    consume
}

// The flow we'll interpret:
// ~produce() | value v |> consume(n: v.num)
//
// Expected: consume receives "42" (the actual value)
// Bug: consume receives "v.num" (the literal string)

const TEST_FLOW =
    \\~produce()
    \\| value v |> consume(n: v.num)
;

~std.interpreter:run(source: TEST_FLOW, dispatcher: dispatch_test)
| result r |> std.io:print.ln("Result: {{ r.value.branch:s }}")
| exhausted e |> std.io:print.ln("Exhausted: {{ e.last_event }}")
| parse_error e |> std.io:print.ln("Parse error: {{ e.message }}")
| validation_error e |> std.io:print.ln("Validation error: {{ e.message }}")
| dispatch_error e |> std.io:print.ln("Dispatch error: {{ e.message }}")