Unreachable Catch

kotlin.unreachable_catch

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Kotlin

Description

Reports a later catch clause whose exception type is a subtype of an earlier catch clause on the same try. Catch clauses are tested top-to-bottom; once a thrown exception matches a clause it is never tested against later clauses, so a later clause catching a subtype of one already covered above is dead code.

Rationale

// Bad
try {
    work()
} catch (e: RuntimeException) {
    log(e)
} catch (e: IllegalStateException) {   // FLAW — already covered above
    log(e)
}

// Good — order specific to general
try {
    work()
} catch (e: IllegalStateException) {
    log(e)
} catch (e: RuntimeException) {
    log(e)
}

The rule uses a conservative, hard-coded map of well-known JDK exception subtype relationships. It does not attempt full type resolution, so it stays silent on third-party or user-defined exception hierarchies — false positives are not worth the noise.

Remediation

Reorder the catch clauses from most-specific to most-general, or delete the unreachable clause entirely if its body duplicates the earlier handler.

References

Kotlin — Exceptions