ArrowFunctionCapturedCounter

warning native off by default PHP ≥ 7.4

Group: Probable bugs

Detect an arrow function updating a captured scalar counter when the same callable is invoked at least twice without reassignment.

Example

<?php
$n = 0; $next = fn() => ++$n; echo $next(), $next();

Reported:

• line 2: Use persistent shared state for this counter.

Detection

• Report an arrow function updating a captured scalar counter when the same callable is invoked at least twice without reassignment.
• Resolve builtin calls and named arguments before checking the contract. Project-local callees are considered only when their bodies or immutable summaries establish the required facts. The default is disabled; enable only when the stated intent matches the application.
• For flow-dependent conditions, require a reachable source-to-use path with no intervening invalidation. Unknown calls, ambiguous aliases or recursion cannot establish definite facts. When the proof is inconclusive, nothing is reported.

Exceptions (no report)

• Parameters, object member updates, single calls, and unknown captured types are excluded.
• Unresolved targets, incomplete required facts, suppressed findings and PHP versions lacking the referenced API or language feature produce no report. User declarations shadowing builtin names are not builtin contracts.

Fix

No automatic fix: choosing reference capture and state lifetime requires intent.

PHP versions

Available from PHP 7.4. Builtin behavior and argument contracts follow the configured PHP version. Extension-specific calls require resolved extension API symbols; do not treat same-named application functions as extension calls.

Options

None. Enable or disable this rule through normal rule configuration.

Configure

In custos.json:

{
  "rules": {
    "ArrowFunctionCapturedCounter": {
      "enabled": true
    }
  }
}

Suppress

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

// @custos-ignore ArrowFunctionCapturedCounter