https://twitter.com/therealyashsriv/status/1219691914523545601

We shouldn't generate code that might cause browser or linting to complain.

https://github.com/facebook/react/blob/0cf22a56a18790ef34c71bef14f64695c0498619/packages/legacy-events/SyntheticEvent.js#L259

It's also just a confusing pattern at best.
return function(arg) {
        if (map.has(arg)) {
          
          
          return map.get(arg);
        }
        const result = fn(arg);
        map.set(arg, result);
        return result;
      };
    }
    return {
      CallExpression: visitCallExpression,
    };
    function visitCallExpression(node) {