Problem

The compat/compat rule produces false positives when local variable or parameter names happen to collide with browser API names. Two related issues:

1. Arrow function / function expression parameters not recognized as local declarations

The Identifier visitor tracks locally declared names to suppress false positives when a name shadows a browser global. However, it only checks these parent node types: Property, FunctionDeclaration, VariableDeclarator, ClassDeclaration, ImportDefaultSpecifier, ImportSpecifier, ImportDeclaration.

Missing: ArrowFunctionExpression and FunctionExpression.

This means callback parameters that share a name with a browser API are flagged:

// Flagged as "scheduler is not supported in Safari 26.2"
// but 'scheduler' here is a domain object, not Window.scheduler
schedulers.map(scheduler => scheduler.name);

// Same issue with function expressions
items.map(function(fetch) { return fetch.toString(); });

2. Early-return guard pattern not recognized as feature detection

The existing isInsideIfStatement check only suppresses errors for API usage inside an if block. The common early-return guard pattern is not detected:

function setup() {
  if (!('serviceWorker' in navigator)) {
    return; // early exit if API unavailable
  }
  // This usage is safe but still flagged:
  navigator.serviceWorker.register('/sw.js');
}

Impact

In a large codebase, these false positives can produce dozens of spurious errors, particularly when domain entities share names with newer browser APIs (e.g. scheduler matching the Prioritized Task Scheduling API Window.scheduler).