Add $result for Return Refinements

[rajshivu]

Updated CreateASTVisitor to map refinement variables '_' and 'return' to '$result' to prevent conflicts.
Verified by manual test in ReturnRefinementTest.java.

[rcosta358]

Hi @rajshivu,
This is not really what we were looking for. Your approach replaces the variables return and _ with $result, which is incorrect and causes the tests to fail.

To allow $result to represent return values of methods, you need to modify the grammar to allow identifiers to start with $, substitute the variable $result with _ (similarly to return), and finally add some tests to check if your implementation is correct.

[rcosta358]

Also, if you have any suggestions other than $result, which is not very idiomatic for Java, feel free to let us know!

[rajshivu]

Hi @rcosta358 ,
Thank you for the clarification - that makes sense. You’re right, my initial approach was too naive and incorrectly replaced return and _ directly with $result, which explains the failing tests.

Based on your feedback, I understand the correct direction is to:

1. Extend the grammar to allow identifiers starting with $.
2. Treat $result as a syntactic alias and internally substitute it with _ (similarly to how return is handled today).
3. Add proper tests to validate that $result, _, and return behave consistently.

I’ll update the implementation accordingly and push a revised PR.
Also, I agree that $result may not be the most idiomatic Java-style identifier — I’ll think about alternative suggestions and share them if I find a better fit.

Thanks again for the guidance, this was very helpful.

[rajshivu]

Fixed the handling of method return values in refinements:
Updated the grammar and AST visitor to allow $result to represent method return values, while still keeping _ as a valid alias.

Added a regression test ResultRefinementRegression.java to verify $result works correctly in refinements.
Ensured existing tests in TestMultiple.java pass with the new $result handling.

Hope This change resolves the issue where return was incorrectly treated as a variable and ensures $result can be safely used in refinement expressions.

[rcosta358]

Hey @rajshivu,
Almost there. Your implementation is not quite correct yet. Currently what you're doing is replacing all return and $result variables with _ in the CreateASTVisitor. That way, the following code passes, when it shouldn't:

void test() {
  @Refinement("$result > 0") // $result is replaced with `_`, which refers to `x`, so it passes
  int x = 1;
}

Actually, $result or return should only be allowed on refinements that target methods, such as:

@Refinement("$result > 0")
int test() {
  return 1;
}

So, we don't actually want to modify the CreateASTVisitor. Instead, we want to modify the MethodsFunctionsChecker. More specifically, the handleFunctionRefinements, and add an additional case for $result, similarly to return:

private Predicate handleFunctionRefinements(RefinedFunction f, CtElement method, List<CtParameter<?>> params) throws LJError {
  // ...
  ret = ret.substituteVariable("return", Keys.WILDCARD);
  ret = ret.substituteVariable("$result", Keys.WILDCARD); // ADD THIS
  f.setRefReturn(ret);
  // ...
}

Finally, please add tests to liquidjava-example/src/main/java/testSuite, not liquidjava-example/src/main/java/testMultiple. For tests that should pass, they must include "Correct" in their file name, whereas for tests that should fail, they should include "Error", along with the expected error in the first line of the file as a comment. To run the tests locally, you can run mvn test.

[rcosta358]

You should also not modify this, since you should include your tests in testSuite and not testMultiple.

[rajshivu]

Hi @rcosta358 ,

Thanks for the clarification! Got it — I’ll revert the changes in CreateASTVisitor and TestMultiple, and instead implement $result handling in MethodsFunctionsChecker.handleFunctionRefinements as suggested. I’ll also move the regression tests to testSuite with the proper naming convention.

[alcides]

Hi @rajshivu, just out of curiosity, how would you pass a Turing test?

[rajshivu]

Hello @alcides , you caught me, I used a bit of AI to help polish my explanation and easy for understand, but I promise there's a real person behind the keyboard.