// if ref is passed and it is not a ref-like, check ref escape,
// since it is the same or narrower than val escape and callee may wrap the ref into a val
// ref escape scope is the narrowest of
// - ref escape of all byref arguments
// - val escape of all byval arguments (ref-like values can be unwrapped into refs, so treat val escape of values as possible ref escape of the result)
//
// val escape scope is the narrowest of
// - val escape of all byval arguments (refs cannot be wrapped into values, so their ref escape is irrelevant, only use val escapes)
// if ref is passed and it is not a ref-like, check ref escape,
// since it is the same or narrower than val escape and callee may wrap the ref into a val
// ref escape scope is the narrowest of
// - ref escape of all byref arguments
// - val escape of all byval arguments (ref-like values can be unwrapped into refs, so treat val escape of values as possible ref escape of the result)
//
// val escape scope is the narrowest of
// - val escape of all byval arguments (refs cannot be wrapped into values, so their ref escape is irrelevant, only use val escapes)