Static check of a MOOL program

The third step in writing a MOOL compiler could be to perform semantic checking during parsing. Since the syntax of the MOOL language is very restrictive, this consists in a limited number of checks.

• When applying the rule F $\longmapsto$ id one should check that id is a variable with an integer value.

• In the ObjectCreation of an object of class A the CallingParameterList must match the FormalParamterList of a NewDeclaration of class A.
• In a MethodCall the CallingParameterList must match the FormalParamterList of the MethodDeclaration.
• In an assignment of the form id := RightValue two cases arise.
  • Either id has not been initialized yet (and so has no known type). Then id refers now to the value of RightValue (which may be an object or an integer).
  • Or id has been initialized yet (and thus has a type) and its type must be that of RightValue (name equivalence). Then id refers now to the value of RightValue (which may be an object or an integer). Otherwise an error must be produced.
• In an assignment of the form AttributeCall := RightValue only one case arises. Indeed, an attribute (even if it has not been initialized yet) has a type. This type must match that of RightValue (here again, just use name equivalence for resolving type equivalence). Then the attribute refers now to the value of RightValue (which may be an object or an integer). Otherwise an error must be produced.

Finally, observe that no overloading resolution is needed.