UnreachableCatchClause

warning native on by default

Group: Probable bugs

An earlier broad catch can intercept every exception a later catch would handle. Put specific exception handlers before broader handlers.

Example

<?php
try { work(); } catch(Throwable $e) {} catch(RuntimeException $e) {}

Reported:

• line 2: Move the specific catch before the broader catch.

Detection

• In one try statement an earlier catch type is identical to, or a proven ancestor/interface of, every type in a later catch clause. Highlight the later clause type list; union catches require all alternatives covered.
• Resolve builtin functions, classes, constants and methods; user-defined lookalikes are excluded. Follow only bounded local proof in one lexical scope.
• Emit one finding per violating operation, not per supporting evidence statement. When the proof is inconclusive, nothing is reported.

Exceptions (no report)

• Do not report unresolved or shadowed builtin names, unknown values, or incomplete receiver/type provenance. Unknown calls, aliases escaping, and intervening writes invalidate local proof. Similar code outside the stated detection contract is not a finding.
• Both standard suppression forms suppress this native ID.

Fix

None. Choosing a repair requires intent or additional runtime information.

PHP versions

Available throughout supported PHP 5.3–8.5 for resolved exception classes. Throwable exists from PHP 7.0; do not infer it on earlier targets. Union catches need PHP 7.1.

Configure

In custos.json:

{
  "rules": {
    "UnreachableCatchClause": {
      "enabled": false
    }
  }
}

Suppress

Before the statement or declaration (or the first statement of the file):

// @custos-ignore UnreachableCatchClause