The type check algorithm for a method invocation expression searches the class hierarchy from the method calls's target class for potential candidate implementations for the method (there may be more than one due ot overloading and overriding). The current selection algorithm filters methods using the types derived for the argument expressions to find the nearest fit. If the call has an expected return type (one which is not the special type Undefined) then this should also be used to select one choice in preference to another.