SaahilClaypool/ExhaustiveMatch

C# generator for discriminated unions

GenerateMatch

Generate a .Match method to switch over types with a known set of cases. The idea is to create expression-style switch statements that ensure all conditions are handled.

The supported types are:

• enums: Match will take function parameters for each case of the enum

• enumeration classes: The source generator will infer each internal class case

  • feature is available in newer version of java

  [GenerateMatch]
  public abstract record Result<T, R>
  {
      public record Ok(T Value): Result<T, R>;
      public record Error(R Message): Result<T, R>;
  }
  
  var res = new Result<int, string>.Ok(100);
  Assert.Equal("100",
      res.Match(ok => ok.Value.ToString(), error => error.Message));
  
  // -- generated -- 
  
  public static class GenericResultExampleMatchExtensions
  {
      public static TReturnType Match<TReturnType, T,  R>
          (this Result<T, R> t,
              Func<Result<T, R>.Ok,TReturnType> whenOk,
              Func<Result<T, R>.Error,TReturnType> whenError)
      {
          if (t is Result<T, R>.Ok t0)
                  return whenOk.Invoke(t0);
          if (t is Result<T, R>.Error t1)
                  return whenError.Invoke(t1);
          throw new Exception("Unreachable");
      }
  
      public static TReturnType Match<TReturnType, T,  R>
          (this Result<T, R> t,
              TReturnType whenOk,
              TReturnType whenError)
      {
          if (t is Result<T, R>.Ok t0)
                  return whenOk;
          if (t is Result<T, R>.Error t1)
                  return whenError;
          throw new Exception("Unreachable");
      }
  }