The Bug Found Writing the Example

Four annotations had no runnable example — @PermuteAnnotation, @PermuteThrows, @PermuteCase, and @PermuteImport. We added AnnotatedCallable2.java to cover all four in one place. Writing it found a bug.

The silent failure in @PermuteCase

The first attempt used a string literal in the body attribute:

@PermuteCase(varName = "k", from = "2", to = "${i}",
             index = "${k}", body = "return \"arg\" + ${k};")

The generated switch had the right number of cases — but each was empty. No body. No error. No warning. Just case 2: falling through to default:.

The cause is in PermuteCaseTransformer.buildSwitchEntry(). It wraps the evaluated body in {...} and calls StaticJavaParser.parseBlock(). If that throws — and it does when the body contains Java string literals — the catch block returns new BlockStmt() silently:

try {
    block = StaticJavaParser.parseBlock("{" + bodyStr + "}");
} catch (Exception e) {
    block = new BlockStmt();  // silent empty fallback
}

The fix: avoid string literals inside body. Primitives work. Method calls work. return String.valueOf(${k}); generates correctly. return "arg" + ${k}; disappears without a word.

The symptom — correctly-numbered cases with no statements — points at the wrong from/to range or annotation placement before it points at a parse failure. It took reading the transformer source to find it.

---

<

Previous Post

Using the Tool on Itself

>

Next Post

From O(N) to O(log N)