Support for Java 8 syntax in aspects

[Ismail Badawi]

It would be nice to be able to use method references (A::b) and lambdas (() -> { }) in aspects.

[Jesper Öqvist]

This is not a priority to fix right now, but it would definitely be nice to support these features. I have been thinking about replacing the JastAdd parser and reuse the ExtendJ parser, which would fix this problem but would also cost too much time.

[Former user]

Is there a chance for this to be prioritized higher? I would love to be able to use the "new" syntax.

[Jesper Öqvist]

I think it's time to postpone the plan to replace the existing JastAdd parser and just add Java 8 features to the one we have now.

I did some testing with lambda expressions and it seemed to work. I'll see if it is possible to add method references too.

[Jesper Öqvist]

I added parsing for lambda expressions, method references, and try-with-resources statements. I might have missed some cases, but at least these lambda variations work now:

aspect Java8_Lambdas {
  // 1. Expression lambdas.

  // Single untyped lambda parameter.
  syn F1 A.untyped1() = i -> i * 2;

  // Multiple untyped lambda parameters.
  syn F2 A.untyped2() = (a, b) -> a / b;
  syn F3 A.untyped3() = (a, b, c) -> a + b - c;

  // Single typed lambda parameter.
  syn F1 A.typed1() = (int i) -> i * i;

  // Multiple untyped lambda parameters.
  syn F2 A.typed2() = (int a, int b) -> a * b;
  syn F3 A.typed3() = (int a, int b, int c) -> a * b / c;

  // 2. Block lambdas.

  // Single untyped lambda parameter.
  syn F1 A.untyped1block() = i -> { return i; };

  // Multiple untyped lambda parameters.
  syn F2 A.untyped2block() = (a, b) -> {
    if (a > b) {
      return a - b;
    } else {
      return b - a;
    }
  };
  syn F3 A.untyped3block() = (a, b, c) -> {
    if (a > b) {
      return (a - b) * c;
    } else {
      return (b - a) * c;
    }
  };

  // Single typed lambda parameter.
  syn F1 A.typed1block() = (int i) -> { return i * i; };

  // Multiple untyped lambda parameters.
  syn F2 A.typed2block() = (int a, int b) -> { return a * b; };
  syn F3 A.typed3block() = (int a, int b, int c) -> { return a * b / c; };

  // Function types:
  interface F0 { int apply(); }
  interface F1 { int apply(int a); }
  interface F2 { int apply(int a, int b); }
  interface F3 { int apply(int a, int b, int c); }
}

If you find Java 8 syntax variations that don't work, please comment here or make a new issue so we can add it to the parser.

[Jesper Öqvist]

Parsing: Java 7 TWR & Java 8 lambdas + methodrefs

fixes #192 (bitbucket)

→ <<cset 7b52108f0359>>

[Jesper Öqvist]

FYI, you can download the latest JastAdd Jar (including this fix) from here: http://jasttest.cs.lth.se:8080/view/JastAdd/job/JastAdd2/lastSuccessfulBuild/artifact/jastadd2.jar

[Former user]

This is great news, thanks! The only case that seems to be missing is a lambda expression without parameters:

Supplier<String> supplier = () -> "foo";

[Jesper Öqvist]

@BjoernPetersen, thank you! I will add that too.

[Jesper Öqvist]

Parsing: empty parameter list in lambda expr

see #192 (bitbucket)

→ <<cset e14131a401ff>>