AspectJ keyword 'before' as lambda argument name causes compile error

[MiniShen]

/**
 * [ERROR] error at
 * [ERROR] util(list, (before, cur) -> before < cur);
 * [ERROR] ^^^^^^^^^^^^^^^^^^^^^^^^
 * [ERROR] C:\workspace\plugin\aspectjTest\src\main\java\fish\Main.java:44:0::0 The left-hand side of an assignment must be a variable [ERROR] error at [ERROR] util(list, (before, cur) -> before < cur);
 */
public static void test() {
  List<Integer> list = new ArrayList<>();
  //1.compile error
  // util(list, (before, cur) -> before < cur);
  //2.compile success
  util(list, (i1, i2) -> i1 < i2);
  //3.compile success
  util(list, (Integer before, Integer cur) -> before < cur);
}

public static <T> void util(Collection<T> list, BiPredicate<T, T> predicate) {}

jdk version：20
aspectj version :1.9.22

[kriegaex]

I can reproduce the problem. As you might know, in native AspectJ syntax before is a keyword. Obviously, the parser is imperfect and does not expect it at this position. This is IMO not a high-priority bug, because a simple workaround is not to use AspectJ keywords as argument names here. Renaming the parameter to beforeX or something else works around the problem.

I am keeping this issue open, however, because in the future when there is development activity again here and no higher priority issue to fix, this can be improved.

Here is a full reproducer class including imports, which can be used for a regression test in the future:

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.BiPredicate;

public class Issue_GH_325_Reproducer {
  public static void test() {
    List<Integer> list = new ArrayList<>();
    // compile error
    util(list, (before, cur) -> before < cur);
    // compile success
    util(list, (i1, i2) -> i1 < i2);
    // compile success
    util(list, (Integer before, Integer cur) -> before < cur);
  }

  public static <T> void util(Collection<T> list, BiPredicate<T, T> predicate) {}
}

$ ajc -v
AspectJ Compiler 1.9.22.1 - Built: Friday May 10, 2024 at 23:23:16 PDT - Eclipse Compiler b2705b00e91be7 (20Mar2024) - Java22 

$ ajc -cp aspectjrt.jar -11 Issue_GH_325_Reproducer.java 
Issue_GH_325_Reproducer.java:10 [error] The left-hand side of an assignment must be a variable
util(list, (before, cur) -> before < cur);
^^^^^^^^^^^^^^^^^^^^^^^^
Issue_GH_325_Reproducer.java:10 [error] Syntax error, insert "InstanceofRHS" to complete Expression
util(list, (before, cur) -> before < cur);
            ^^^^^^
Issue_GH_325_Reproducer.java:10 [error] Syntax error, insert ")" to complete Expression
util(list, (before, cur) -> before < cur);
            ^^^^^^
Issue_GH_325_Reproducer.java:10 [error] Syntax error on token "->", invalid AssignmentOperator
util(list, (before, cur) -> before < cur);
                         ^^
Issue_GH_325_Reproducer.java:10 [error] Syntax error on token ")", delete this token
util(list, (before, cur) -> before < cur);
                                        ^

5 errors

Please note my July 2024 message to the aspectj-users and aspectj-announce mailing lists regarding my situation as an AspectJ maintainer.