In the spec, this happens in the EvaluateCall abstract operation
(https://tc39.es/ecma262/#sec-evaluatecall), and the order is defined
as:
3. Let argList be ? ArgumentListEvaluation of arguments.
4. If Type(func) is not Object, throw a TypeError exception.
5. If IsCallable(func) is false, throw a TypeError exception.
In LibJS this is handled by CallExpression::execute(), which had the
callee function check first and would therefore never evaluate the
arguments for a non-function callee.
