// Created by parser
Program ::= Block /PredefinedType:TypeDecl*/;
Block ::= BlockStmt*;
abstract BlockStmt;
abstract Stmt: BlockStmt;
abstract Decl: BlockStmt ::= <Name:String>;
abstract TypeDecl:Decl;
ClassDecl: TypeDecl ::= [Superclass:IdUse] Body:Block;
VarDecl: Decl ::= Type:Access;
AssignStmt: Stmt ::= Variable:Access Value:Exp;
WhileStmt: Stmt ::= Condition:Exp Body:Stmt;
abstract Exp;
abstract Access:Exp;
abstract IdUse: Access ::= <Name:String>;
Use: IdUse;
Dot:Access ::= ObjectReference:Access IdUse;
BooleanLiteral : Exp ::= <Value:String>;

// Created by NTA equations
PrimitiveDecl: TypeDecl;
UnknownDecl: TypeDecl;

// Created by Rewrites
TypeUse : IdUse;
VariableUse : IdUse; 


// EXPLANATION OF THE CLASSES
// *Program*: the root of the AST. It contains a block and a nonterminal attribute holding a
//     list of predefined type declarations (added to the AST during attribute evaluation).
// *Block*: contains a list of BlockStmt.
// *BlockStmt*:  either a declaration or an ordinary statement.
//     I.e., it is the kind of thing that can appear immediately inside a block.
// *Stmt*: an ordinary imperative statement, like an assignment or a while-statement.
// *Decl*: a declaration of some named entity.
// *TypeDecl*: a declaration of a type, e.g., classes and primitive types like int.
// *ClassDecl*: a declaration of a class.
//     In addition to the name, it has an optional superclass and a block.
// *VarDecl*: a declaration of a variable. In addition to the name, It has a type.
// *AssignStmt*: an assignment statement with a left-hand side variable and a right-hand side
//     value in the form of an expression.
// *WhileStmt*: a while statement with a condition and a loop body.
// *Exp*: an expression
// *Access*: an expression that accesses a declared entity in the program.
// *IdUse*: an access that is a simple identifier
// *Use*: An IdUse whose declaration kind is not yet known. Replaced by rewrite rules.
// *Dot*: a qualified access with an object reference and a identifier naming an entity in that object.

// *PrimitiveDecl*: a declaration of a primitive type, e.g., boolean or int. Created by NTA equation.
// *UnknownDecl*: represents missing or otherwise unknown declarations. Created by NTA equation.
 
// *TypeUse*: an IdUse that is bound to a type declaration. Result of context-dependent rewrite from Use node.
// *VariableUse*: an IdUse that is bound to a variable declaration. Result of context-dependent rewrite from Use node.