isFunction() or isCallable() type queries?

[elichten94]

It would be useful to have a utility method that can query if a Type<ts.Type> is callable.

The existing queries that can be performed on a Type<ts.Type>, such as isObject(), isNumber(), isLiteral(), etc. seem straightforward, though I don't see anything to check if a type is a method, function, callable etc.

A callable type could be far up an inheritance chain from the raw Function or (...args: any[]) => any types, so I assume this could be difficult to check. I also noticed that isObject() returns true for callables (since they're considered first class objects in js/ts anyway).

I've considered the following alternative, though it doesn't seem to work as expected, might have some risky edgecases, and and looks expensive to run.

export const isCallableType = (typeNode: Node): boolean => {
  const isCallable =
    Node.isFunctionDeclaration(typeNode) ||
    Node.isFunctionExpression(typeNode) ||
    Node.isCallSignatureDeclaration(typeNode) ||
    Node.isFunctionLikeDeclaration(typeNode) ||
    Node.isFunctionTypeNode(typeNode) ||
    Node.isArrowFunction(typeNode) ||
  if (isCallable) {
    return true;
  } else {
    if (typeNode.getChildren().length === 0) {
      return false;
    } else {
      return typeNode.getChildren().some((child) => isCallableType(child));
    }
  }
};