fixhunt

biome style/noUselessElse

labelled safe
Runs / 2026-10-22T17-25-04-554Z-t601-biome-style_noUselessElsebiome 2.5.152026-10-22 17:25 UTC6 programs × 1 round(s)6 programs, 1 fired, 1 fixed, 0 findings, 5 rejectedmodel cost $0.0018

Analysis Nemotron 3 Super

The rule flags else blocks following an if statement whose body contains a breaking statement (return, break, continue, throw), marking them as unnecessary.

Fix: Remove the else block and promote its statements to the same indentation level as the if statement, preserving their original order.

12 hazards
  • Moving a var declaration from the else block to the outer scope changes its scoping from block-scoped to function-scoped, potentially causing hoisting issues or name collisions.
  • If the else block contains a labeled break/continue targeting an outer label, promoting it may alter which loop or switch the label refers to due to changed nesting depth.
  • Promoting a throw statement from the else block may change exception handling if the if statement was inside a try block whose catch clause no longer captures the thrown value due to altered control flow.
  • If the else block contains a function declaration, moving it to the outer scope may cause early hoisting and unintended availability before the if statement executes.
  • When the else block holds a const/let variable that shadows an outer variable, promoting it may cause a syntax error due to duplicate declaration in the same block scope.
  • Comments attached to the else block (e.g., // comment else { ... }) may be lost during the rewrite if the tool does not preserve leading or trailing comments on the removed block.
  • If the if statement is part of a larger conditional chain (e.g., else if), removing the else may incorrectly merge logic or alter the intended branching structure.
  • Promoting statements from the else block may change evaluation order relative to side effects in the if condition or preceding expressions if those expressions rely on timing.
  • In strict mode, promoting a with statement from the else block is invalid and will cause a SyntaxError since with is not allowed in strict mode at any scope.
  • If the else block contains a debugger statement, moving it may alter debugging behavior if tooling associates breakpoints with specific syntactic contexts.
  • When the else block is empty, the fix removes it entirely, but if it contained only a comment, that comment may be dropped even though it had semantic intent (e.g., TODO or license notice).
  • If the if condition has a side effect (e.g., function call) and the else block contains a break, promoting the break may cause it to exit a different loop than intended due to altered nesting.

Programs

idresulttitlehazard
r1-p001invalidNumeric/String Coercion with + vs Template LiteralPromoting else block changes coercion behavior due to interaction between + operator and template literals when evaluating expressions like `+[]` vs `${}`.
r1-p002invalidEvaluation Order Change Due to Side Effects in ConditionPromoting else block moves its statements before the if condition's side effects, altering execution order when condition has observable side effects.
r1-p003invalidOrder of Evaluation with Side Effects in ExpressionsPromoting else block causes expressions in it to be evaluated before the if condition, changing order of side effects when both contain mutations.
r1-p004fix okBreak Promoted to Wrong Loop Nesting LevelPromoting a break from else block changes which loop it exits due to altered nesting after fix, causing unintended loop termination.
r1-p005invalidASI Hazard: Leading Parenthesis After Promoted Else BlockAfter removing else block, promoted statements may begin with '(' causing ASI to incorrectly attach it to prior expression, changing meaning.
r1-p006invalidComment Dropped from Empty Else BlockWhen else block contains only a comment (e.g., TODO), the fix removes the entire block, dropping the comment despite its semantic intent.

Sources

r1-p001 · Numeric/String Coercion with + vs Template Literal (generated program does not parse: /home/sun/dev/diaghunt/runs/2026-10-22T17-25-0)
1let x = [];
2if (x == 0) { return; } else {
3 console.log(+x + `${x}`);
4}
5console.log('end');
r1-p002 · Evaluation Order Change Due to Side Effects in Condition (generated program does not parse: /home/sun/dev/diaghunt/runs/2026-10-22T17-25-0)
1let log = [];
2function f() { log.push('cond'); return true; }
3if (f()) { return; } else {
4 log.push('else');
5}
6console.log(log.join(','));
r1-p003 · Order of Evaluation with Side Effects in Expressions (generated program does not parse: /home/sun/dev/diaghunt/runs/2026-10-22T17-25-0)
1let a = 0, b = 0;
2if (++a) { return; } else {
3 b = ++a;
4 console.log(a + ',' + b);
5}
6console.log('done');
r1-p004 · Break Promoted to Wrong Loop Nesting Level
1outer: for (let i = 0; i < 2; i++) {
2 for (let j = 0; j < 2; j++) {
3 if (i === 1) { break outer; } else {
4 break; // inner break
5 }
6 }
7}
8console.log('escaped');
--- orig.js	2026-10-22 13:25:14.561793583 -0400
+++ fixed.js	2026-10-22 13:25:16.525825997 -0400
@@ -1,8 +1,7 @@
 outer: for (let i = 0; i < 2; i++) {
   for (let j = 0; j < 2; j++) {
-    if (i === 1) { break outer; } else {
+    if (i === 1) { break outer; }
       break; // inner break
-    }
   }
 }
 console.log('escaped');

escaped
r1-p005 · ASI Hazard: Leading Parenthesis After Promoted Else Block (generated program does not parse: /home/sun/dev/diaghunt/runs/2026-10-22T17-25-0)
1let y = 1
2if (y) { return; } else {
3 (function(){ y = 2; })()
4}
5console.log(y)
r1-p006 · Comment Dropped from Empty Else Block (generated program does not parse: /home/sun/dev/diaghunt/runs/2026-10-22T17-25-0)
1// License: MIT
2if (false) { return; } else {
3 // TODO: handle true case
4}
5console.log('executed')