fn: add note and hush partial bijections

fn/either_test.go

@@ -100,7 +100,7 @@ func TestPropToOptionIdentities(t *testing.T) {
 			e = NewRight[int, string](s)
 
 			r2O := e.RightToOption() == Some(s)
-			o2R := e == OptionToRight[string, int, string](
+			o2R := e == OptionToRight[string, int](
 				Some(s), i,
 			)
 			l2O := e.LeftToOption() == None[int]()
@@ -109,7 +109,7 @@ func TestPropToOptionIdentities(t *testing.T) {
 		} else {
 			e = NewLeft[int, string](i)
 			l2O := e.LeftToOption() == Some(i)
-			o2L := e == OptionToLeft[int, int](Some(i), s)
+			o2L := e == OptionToLeft[int](Some(i), s)
 			r2O := e.RightToOption() == None[string]()
 
 			return l2O && o2L && r2O

fn/option.go

@@ -1,6 +1,9 @@
 package fn
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 // Option[A] represents a value which may or may not be there. This is very
 // often preferable to nil-able pointers.
@@ -216,7 +219,7 @@ func (o Option[A]) UnsafeFromSome() A {
 
 // OptionToLeft can be used to convert an Option value into an Either, by
 // providing the Right value that should be used if the Option value is None.
-func OptionToLeft[O, L, R any](o Option[O], r R) Either[O, R] {
+func OptionToLeft[O, R any](o Option[O], r R) Either[O, R] {
 	if o.IsSome() {
 		return NewLeft[O, R](o.some)
 	}
@@ -226,10 +229,18 @@ func OptionToLeft[O, L, R any](o Option[O], r R) Either[O, R] {
 
 // OptionToRight can be used to convert an Option value into an Either, by
 // providing the Left value that should be used if the Option value is None.
-func OptionToRight[O, L, R any](o Option[O], l L) Either[L, O] {
+func OptionToRight[O, L any](o Option[O], l L) Either[L, O] {
 	if o.IsSome() {
 		return NewRight[L, O](o.some)
 	}
 
 	return NewLeft[L, O](l)
 }
+
+// Note allows you to convert an Option value to a result with your own error
+// message.
+func (o Option[A]) Note(errString string, args ...interface{}) Result[A] {
+	return Result[A]{
+		OptionToLeft[A, error](o, fmt.Errorf(errString, args...)),
+	}
+}

fn/result.go

@@ -81,11 +81,23 @@ func (r Result[T]) Option() Option[T] {
 	return r.Either.LeftToOption()
 }
 
+// Hush mutes the error value of the result.
+func (r Result[T]) Hush() Option[T] {
+	return r.Either.LeftToOption()
+}
+
 // WhenResult executes the given function if the Result is a success.
+//
+// Deprecated: Use WhenOk instead.
 func (r Result[T]) WhenResult(f func(T)) {
 	r.WhenLeft(f)
 }
 
+// WhenOk executes the given function if the Result is a success.
+func (r Result[T]) WhenOk(f func(T)) {
+	r.WhenLeft(f)
+}
+
 // WhenErr executes the given function if the Result is an error.
 func (r Result[T]) WhenErr(f func(error)) {
 	r.WhenRight(f)