func (tv TypeAndValue) Assignable() bool {
	return tv.mode == variable || tv.mode == mapindex
}

// HasOk reports whether the corresponding expression may be
// used on the rhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
	return tv.mode == commaok || tv.mode == mapindex
}

// Instance reports the type arguments and instantiated type for type and