4.8.4 TC-4 Code to Write

What is to be done.

ast::Typable

ast::TypeConstructor

Because many AST nodes will be annotated with their type, the feature is factored by these two classes. See Typable, and TypeConstructor, for details.

ast::Exp, ast::Dec, ast::Ty

These are typable.

ast::FunctionDec, ast::TypeDec, ast::Ty

These build types.

src/type/type.*,

src/type/array.*,

src/type/builtin-types.*,

src/type/class.*,

src/type/function.*,

src/type/method.*,

src/type/named.*,

src/type/nil.*,

src/type/record.*

Implement the Singletons type::String, type::Int, and type::Void. Using templates would be particularly appreciated to factor the code between the three singleton classes, see TC-4 Options.

The remaining classes are incomplete.

Pay extra attention to type::operator==(const Type& a, const Type& b) and type::Type::compatible_with.

type::TypeChecker

object::TypeChecker

Of course this is the most tricky part. We hope there are enough comments in there so that you understand what is to be done. Please, post your questions and help us improve it.

It is also the type::TypeChecker’s job to set the record_type in the type::Nil class. record_type is holding some information about the type::Record type associated to the type::Nil type. We choose to handle the record_type only when no error occured in the type-checking process.

type::GenVisitor

type::GenDefaultVisitor

type::Types are visitable. You must implement the default visitor class template, which walks through the tree of types doing nothing. It’s used as a base class for the type visitors.

type::PrettyPrinter

In order to output nice error messages, the types need to be printed. You must implement a visitor that prints the types, similar to ast::PrettyPrinter.

Computing the Escaping Variables

The implementation of TC-E, suggested at TC-3, becomes a mandatory assignment at TC-4.