duplicated-branch-tail

Availability: default-on; no policy required. Severity info, confidence high for the resolved source observation. Use --min-severity low to hide informational findings.

Reports one to seven expression statements and an explicit return copied between the end of a terminating branch and its immediate following continuation. Both copies must resolve to the same symbols, operations, types and expression tree. This is source duplication across alternative routes, not duplicate execution.

Example and review scenario#

For example:

if (disclose(flag)) {
  round.increment(1);
  return [];
}
round.increment(1);
return [];

Each route increments once. Consider sharing the tail after any branch-specific work. The finding is a source-quality observation, not an authorization or monetary defect.

False positives and limitations#

Authors may deliberately keep alternative routes visually independent. Identical resolved source is the fact reported; removal or hoisting is a review decision. Preserve return behavior, proof constraints, disclosure and transaction ordering. No optimized compiler/prover cost reduction is claimed.

Resolved circuit bodies in the compilation unit are examined, including imported instances and calls in source-excluded code. Unresolved unused library APIs are outside this observation; this is not a whole-library analysis. Unknown conditions retain both alternatives; source-constant excluded branches and unreachable suffixes are quiet. Bindings, callbacks, nested control inside the copied tail, implicit returns, longer tails and merely value-equivalent expressions are outside the contract. Same-name references that resolve differently stay quiet. Exhausted source traversal produces explicit rule-scoped incomplete diagnostics for every entry. Baseline transfer completion and unrelated rules remain independently reported. With no entry row, exhaustion retains an explicit root diagnostic.