fix: use correct signature on bind

Base.Tests/Structures/MaybeTests.cs

@@ -0,0 +1,45 @@
+using FruityFoundation.Base.Structures;
+using NUnit.Framework;
+
+namespace Base.Tests.Structures;
+
+public class MaybeTests
+{
+	[Test]
+	public void TestBind_DoesNotBindEmptyValue()
+	{
+		var emptyMaybe = Maybe.Empty<int>();
+
+		var result = emptyMaybe.Bind(x => Maybe.Just(x + 1));
+
+		Assert.That(result, Is.InstanceOf<Maybe<int>>());
+		Assert.That(result.HasValue, Is.False);
+	}
+
+	[Test]
+	public void TestBind_BindsWhenHasValue()
+	{
+		var emptyMaybe = Maybe.Just<int>(1);
+
+		var result = emptyMaybe.Bind(x => Maybe.Just(x + 1));
+
+		Assert.That(result, Is.InstanceOf<Maybe<int>>());
+		Assert.That(result.HasValue, Is.True);
+		Assert.That(result.Value, Is.EqualTo(2));
+	}
+
+	[Test]
+	public void TestBind_BindsWhenHasValue_NewOutputType()
+	{
+		var maybe = Maybe.Just(25);
+
+		var result = maybe.Bind(x => x switch
+		{
+			25 => Maybe.Just("twenty-five"),
+			_ => Maybe.Empty<string>()
+		});
+
+		Assert.That(result, Is.InstanceOf<Maybe<string>>());
+		Assert.That(result.HasValue, Is.True);
+	}
+}

Base/Structures/Maybe.cs

@@ -54,7 +54,7 @@ public readonly struct Maybe<T>
 	public Maybe<TOutput> Map<TOutput>(Func<T, TOutput> transformer) =>
 		HasValue ? Maybe.Just(transformer(Value)) : Maybe.Empty<TOutput>();
 
-	public Maybe<TOutput> Bind<TOutput>(Func<T, TOutput> binder) =>
+	public Maybe<TOutput> Bind<TOutput>(Func<T, Maybe<TOutput>> binder) =>
 		HasValue ? binder(Value) : Maybe.Empty<TOutput>();
 
 	public Maybe<TOutput> Cast<TOutput>()