Merge pull request #728 from polyadic/discard

Funcky/Discard.cs

@@ -0,0 +1,19 @@
+namespace Funcky;
+
+public static class Discard
+{
+    /// <summary>A convenient shortcut for getting a <see cref="Unit"/>.
+    /// Useful for using switch expressions purely with guards when matching on non-constant values
+    /// or as an alternative to <c>if</c> / <c>else if</c> / <c>else</c> chains.</summary>
+    /// <example><code>
+    /// using static Funcky.Discard;
+    /// return __ switch
+    /// {
+    ///     _ when user.IsFrenchAdmin() => "le sécret",
+    ///     _ when user.IsAdmin() => "secret",
+    ///     _ => "(redacted)",
+    /// };
+    /// </code></example>
+    /// <remarks>The name is intentionally two underscores as to not conflict with C#'s discard syntax.</remarks>
+    public static readonly Unit __ = Unit.Value;
+}

Funcky/PublicAPI.Shipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
+Funcky.Discard
 Funcky.EitherOrBoth
 Funcky.EitherOrBoth<TLeft, TRight>
 Funcky.EitherOrBoth<TLeft, TRight>.EitherOrBoth() -> void
@@ -773,3 +774,4 @@ static Funcky.Unit.operator ==(Funcky.Unit left, Funcky.Unit right) -> bool
 static Funcky.Unit.operator >(Funcky.Unit left, Funcky.Unit right) -> bool
 static Funcky.Unit.operator >=(Funcky.Unit left, Funcky.Unit right) -> bool
 static Funcky.Unit.Value.get -> Funcky.Unit
+static readonly Funcky.Discard.__ -> Funcky.Unit

changelog.md

@@ -17,6 +17,20 @@ var greeting = person switch
 record Person(string FirstName, Option<string> LastName);
 ```
 
+### Discard
+The new `Discard.__` field provides a short-hand for `Unit.Value` to be used with `switch` expressions.
+
+```cs
+using static Funcky.Discard;
+
+return __ switch
+{
+    _ when user.IsFrenchAdmin() => "le sécret",
+    _ when user.IsAdmin() => "secret",
+    _ => "(redacted)",
+};
+```
+
 ### Retry with Exception
 We've added overloads to the `Retry` and `RetryAsync` functions that allow retrying a function
 as long as an exception is thrown.