fn: add transpositions for Option and Result

fn/option_test.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"testing"
+	"testing/quick"
 
 	"github.com/stretchr/testify/require"
 )
@@ -26,3 +27,27 @@ func TestSomeToOkf(t *testing.T) {
 		Err[uint8](fmt.Errorf(errStr)),
 	)
 }
+
+func TestPropTransposeOptResInverts(t *testing.T) {
+	f := func(i uint) bool {
+		var o Option[Result[uint]]
+		switch i % 3 {
+		case 0:
+			o = Some(Ok(i))
+		case 1:
+			o = Some(Errf[uint]("error"))
+		case 2:
+			o = None[Result[uint]]()
+		default:
+			return false
+		}
+
+		odd := TransposeOptRes(o) ==
+			TransposeOptRes(TransposeResOpt(TransposeOptRes(o)))
+		even := TransposeResOpt(TransposeOptRes(o)) == o
+
+		return odd && even
+	}
+
+	require.NoError(t, quick.Check(f, nil))
+}