+ # Is the expression node correcly typed
+ # Return false if typed was not yet computed or
+ # if an error occured during the typing computation
+ meth is_typed: Bool is abstract
+
+ # Is the expression node a statement? (ie has no return value)
+ # require: is_typed
+ meth is_statement: Bool is abstract
+
+ # The static type of the expression
+ # require: is_typed and not is_statement