Use Go standard-library values

This recipe stays on the direct Go boundary. It uses an imported bytes.Buffer value, calls its pointer-receiver methods through addressable local storage, keeps both results from Go APIs visible, and passes a typed arrow back into Go.

Project tree

go-standard-library/
└── main.km

Source

import go bytes from "bytes";
import go fmt from "fmt";
import go sort from "sort";
import go strconv from "strconv";
import go strings from "strings";

function main(): void {
  let buffer: bytes.Buffer = bytes.Buffer {};
  const [written, writeErr] = buffer.WriteString(strings.ToUpper("hello"));
  const [parsedNumber, parseErr] = strconv.Atoi("42");
  const values = [3, 1, 2];
  sort.Slice(values, (left: int, right: int): boolean => values[left] < values[right]);

  fmt.Println(
    written,
    writeErr === nil,
    buffer.String(),
    parsedNumber,
    parseErr === nil,
    values,
  );
}

Run

keika check main.km
keika run main.km

Expected output:

5 true HELLO 42 true [1 2 3]

Read the boundary

1. bytes.Buffer keeps the identity and method set of the real Go type.
2. buffer is a named, addressable value. The compiler can therefore call WriteString and String, whose Go method set includes pointer-receiver behavior.
3. The nested strings.ToUpper call finishes before WriteString starts; each target and argument evaluates once in source order.
4. WriteString and strconv.Atoi expose their Go results directly. [written, writeErr] and [parsedNumber, parseErr] are compiler-known result lists, not tuple objects.
5. Raw Go error values compare with nil. Nothing converts them to exceptions or hides them behind a result wrapper.
6. sort.Slice receives a Kinmokusei arrow with the exact Go callback shape. The arrow captures values lexically and Go calls it during sorting.

Use Result<T> and postfix ? when propagation is part of your own function contract. Keep explicit results when the current scope must inspect, combine, or report them separately.

Continue with the Go interoperability guide, the interop support matrix, or Result parsing.