(Nonfunctional) Implemented many type-checking rules

5 files changed, 761 insertions, 4 deletions

diff --git a/minijava/PPrinter.java b/minijava/PPrinter.java
index 7dd484b..aed7ec4 100644
--- a/minijava/PPrinter.java
+++ b/minijava/PPrinter.java
@@ -1,8 +1,5 @@
-//
-// Generated by JTB 1.3.2
-//
-
 package minijava;
+
 import syntaxtree.*;
 import visitor.*;
 import java.util.*;
diff --git a/minijava/SymTableVis.java b/minijava/SymTableVis.java
new file mode 100644
index 0000000..3d8003b
--- /dev/null
+++ b/minijava/SymTableVis.java
@@ -0,0 +1,43 @@
+package minijava;
+
+import syntaxtree.*;
+import visitor.*;
+import java.util.*;
+
+/**
+ * Provides default methods which visit each node in the tree in depth-first
+ * order.  Your visitors may extend this class.
+ */
+public class SymTableVis<R,A> implements GJVisitor<R,A> {
+
+    public HashMap<String,String> symt = new HashMap<>();
+
+    private void print_filter(String message) {
+        boolean debug = true;
+        if (debug)
+            System.out.println(message);
+    }
+
+    public R visit(VarDeclaraction n, A argu) {
+        R _ret=null;
+
+        this.print_filter("Processing declaration");
+
+        String type = "";
+        switch (n.f0.f0.which) {
+        case 2:
+            type = "Int"; break;
+        default:
+            this.print_filter("Unsupported case");
+        }
+
+        String id = n.f1.f0.tokenImage;
+
+        this.printfilter("Inserting " + id + " => " + type);
+        // Safe?
+        symt.put(id, type);
+
+        return _ret;
+    }
+
+}
diff --git a/minijava/TypeCheckSimp.java b/minijava/TypeCheckSimp.java
new file mode 100644
index 0000000..01f8b27
--- /dev/null
+++ b/minijava/TypeCheckSimp.java
@@ -0,0 +1,683 @@
+package minijava;
+
+import syntaxtree.*;
+import visitor.*;
+import java.util.*;
+
+/**
+ * Provides default methods which visit each node in the tree in depth-first
+ * order.  Your visitors may extend this class.
+ */
+public class TypeCheckSimp implements GJVisitor<TypeInstance,HashMap<String,String>> {
+
+    private void print_filter(String message) {
+	boolean debug = true;
+	if (debug)
+	    System.out.println(message);
+    }
+    //
+    // Auto class visitors--probably don't need to be overridden.
+    //
+    public TypeInstance visit(NodeList n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	int _count=0;
+	for ( Enumeration<Node> e = n.elements(); e.hasMoreElements(); ) {
+	    e.nextElement().accept(this,argu);
+	    _count++;
+	}
+	return _ret;
+    }
+
+    public TypeInstance visit(NodeListOptional n, HashMap<String,String> argu) {
+	if ( n.present() ) {
+	    TypeInstance _ret=null;
+	    int _count=0;
+	    for ( Enumeration<Node> e = n.elements(); e.hasMoreElements(); ) {
+		e.nextElement().accept(this,argu);
+		_count++;
+	    }
+	    return _ret;
+	}
+	else
+	    return null;
+    }
+
+    public TypeInstance visit(NodeOptional n, HashMap<String,String> argu) {
+	if ( n.present() )
+	    return n.node.accept(this,argu);
+	else
+	    return null;
+    }
+
+    public TypeInstance visit(NodeSequence n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	int _count=0;
+	for ( Enumeration<Node> e = n.elements(); e.hasMoreElements(); ) {
+	    e.nextElement().accept(this,argu);
+	    _count++;
+	}
+	return _ret;
+    }
+
+    public TypeInstance visit(NodeToken n, HashMap<String,String> argu) { return null; }
+
+    //
+    // User-generated visitor methods below
+    //
+
+    /**
+     * f0 -> MainClass()
+     * f1 -> ( TypeDeclaration() )*
+     * f2 -> <EOF>
+     */
+    public TypeInstance visit(Goal n, HashMap<String,String> argu) {
+	TypeInstance ret = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return ret;
+    }
+
+    /**
+     * f0 -> "class"
+     * f1 -> Identifier()
+     * f2 -> "{"
+     * f3 -> "public"
+     * f4 -> "static"
+     * f5 -> "void"
+     * f6 -> "main"
+     * f7 -> "("
+     * f8 -> "String"
+     * f9 -> "["
+     * f10 -> "]"
+     * f11 -> Identifier()
+     * f12 -> ")"
+     * f13 -> "{"
+     * f14 -> ( VarDeclaration() )*
+     * f15 -> ( Statement() )*
+     * f16 -> "}"
+     * f17 -> "}"
+     */
+    public TypeInstance visit(MainClass n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance name = n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	n.f6.accept(this, argu);
+	n.f7.accept(this, argu);
+	n.f8.accept(this, argu);
+	n.f9.accept(this, argu);
+	n.f10.accept(this, argu);
+	TypeInstance args = n.f11.accept(this, argu);
+	n.f12.accept(this, argu);
+	n.f13.accept(this, argu);
+	TypeInstance var_dec = n.f14.accept(this, argu);
+	TypeInstance stmt = n.f15.accept(this, argu);
+	n.f16.accept(this, argu);
+	n.f17.accept(this, argu);
+	return stmt;
+    }
+
+    /**
+     * f0 -> ClassDeclaration()
+     *               | ClassExtendsDeclaration()
+     */
+    public TypeInstance visit(TypeDeclaration n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> "class"
+     * f1 -> Identifier()
+     * f2 -> "{"
+     * f3 -> ( VarDeclaration() )*
+     * f4 -> ( MethodDeclaration() )*
+     * f5 -> "}"
+     */
+    public TypeInstance visit(ClassDeclaration n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> "class"
+     * f1 -> Identifier()
+     * f2 -> "extends"
+     * f3 -> Identifier()
+     * f4 -> "{"
+     * f5 -> ( VarDeclaration() )*
+     * f6 -> ( MethodDeclaration() )*
+     * f7 -> "}"
+     */
+    public TypeInstance visit(ClassExtendsDeclaration n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	n.f6.accept(this, argu);
+	n.f7.accept(this, argu);
+	return _ret;
+    }
+
+    // FIXME
+    /**
+     * f0 -> Type()
+     * f1 -> Identifier()
+     * f2 -> ";"
+     */
+    public TypeInstance visit(VarDeclaration n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return new TypeInstance(TypeEnum.CHECK);
+    }
+
+    /**
+     * f0 -> "public"
+     * f1 -> Type()
+     * f2 -> Identifier()
+     * f3 -> "("
+     * f4 -> ( FormalParameterList() )?
+     * f5 -> ")"
+     * f6 -> "{"
+     * f7 -> ( VarDeclaration() )*
+     * f8 -> ( Statement() )*
+     * f9 -> "return"
+     * f10 -> Expression()
+     * f11 -> ";"
+     * f12 -> "}"
+     */
+    public TypeInstance visit(MethodDeclaration n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	n.f6.accept(this, argu);
+	n.f7.accept(this, argu);
+	n.f8.accept(this, argu);
+	n.f9.accept(this, argu);
+	n.f10.accept(this, argu);
+	n.f11.accept(this, argu);
+	n.f12.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> FormalParameter()
+     * f1 -> ( FormalParameterRest() )*
+     */
+    public TypeInstance visit(FormalParameterList n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> Type()
+     * f1 -> Identifier()
+     */
+    public TypeInstance visit(FormalParameter n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> ","
+     * f1 -> FormalParameter()
+     */
+    public TypeInstance visit(FormalParameterRest n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> ArrayType()
+     *               | BooleanType()
+     *               | IntegerType()
+     *               | Identifier()
+     */
+    public TypeInstance visit(Type n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> "int"
+     * f1 -> "["
+     * f2 -> "]"
+     */
+    public TypeInstance visit(ArrayType n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return new TypeInstance(TypeEnum.int_array);
+    }
+
+    /**
+     * f0 -> "boolean"
+     */
+    public TypeInstance visit(BooleanType n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> "int"
+     */
+    public TypeInstance visit(IntegerType n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> Block()
+     *               | AssignmentStatement()
+     *               | ArrayAssignmentStatement()
+     *               | IfStatement()
+     *               | WhileStatement()
+     *               | PrintStatement()
+     */
+    public TypeInstance visit(Statement n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> "{"
+     * f1 -> ( Statement() )*
+     * f2 -> "}"
+     */
+    public TypeInstance visit(Block n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return ret;
+    }
+
+    /**
+     * f0 -> Identifier()
+     * f1 -> "="
+     * f2 -> Expression()
+     * f3 -> ";"
+     */
+    public TypeInstance visit(AssignmentStatement n, HashMap<String,String> argu) {
+	TypeInstance lhs = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance rhs = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	return (lhs.equal_type(rhs)) ?
+	    new TypeInstance(TypeEnum.CHECK) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> Identifier()
+     * f1 -> "["
+     * f2 -> Expression() //int
+     * f3 -> "]"
+     * f4 -> "="
+     * f5 -> Expression() //int
+     * f6 -> ";"
+     */
+    public TypeInstance visit(ArrayAssignmentStatement n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance index = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	TypeInstance value = n.f5.accept(this, argu);
+	n.f6.accept(this, argu);
+	return (index.get_type() == TypeEnum.integer &&
+		value.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.CHECK) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> "if"
+     * f1 -> "("
+     * f2 -> Expression()
+     * f3 -> ")"
+     * f4 -> Statement()
+     * f5 -> "else"
+     * f6 -> Statement()
+     */
+    public TypeInstance visit(IfStatement n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance expr = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	TypeInstance stmt1 = n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	TypeInstance stmt2 = n.f6.accept(this, argu);
+	return (expr.get_type() == TypeEnum.bool &&
+		stmt1.get_type() == stmt2.get_type() == TypeEnum.CHECK) ?
+	    new TypeInstance(TypeEnum.CHECK) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> "while"
+     * f1 -> "("
+     * f2 -> Expression()
+     * f3 -> ")"
+     * f4 -> Statement()
+     */
+    public TypeInstance visit(WhileStatement n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance expr = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	TypeInstance stmt = n.f4.accept(this, argu);
+	return (expr.get_type() == TypeEnum.bool &&
+		stmt.get_type() == TypeEnum.CHECK) ?
+	    new TypeInstance(TypeEnum.CHECK) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> "System.out.println"
+     * f1 -> "("
+     * f2 -> Expression()
+     * f3 -> ")"
+     * f4 -> ";"
+     */
+    public TypeInstance visit(PrintStatement n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance ret = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	return (ret.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.CHECK) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> AndExpression()
+     *               | CompareExpression()
+     *               | PlusExpression()
+     *               | MinusExpression()
+     *               | TimesExpression()
+     *               | ArrayLookup()
+     *               | ArrayLength()
+     *               | MessageSend()
+     *               | PrimaryExpression()
+     */
+    public TypeInstance visit(Expression n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> PrimaryExpressionppp()
+     * f1 -> "&&"
+     * f2 -> PrimaryExpression()
+     */
+    public TypeInstance visit(AndExpression n, HashMap<String,String> argu) {
+	TypeInstance oper1 = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance oper2 = n.f2.accept(this, argu);
+	return (oper1.get_type() == TypeEnum.bool &&
+		oper2.get_type() == TypeEnum.bool) ?
+	    new TypeInstance(TypeEnum.bool) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "<"
+     * f2 -> PrimaryExpression()
+     */
+    public TypeInstance visit(CompareExpression n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	TypeInstance oper1 = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance oper2 = n.f2.accept(this, argu);
+	return (oper1.get_type() == TypeEnum.integer &&
+		oper2.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.bool) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "+"
+     * f2 -> PrimaryExpression()
+     */
+    public TypeInstance visit(PlusExpression n, HashMap<String,String> argu) {
+	TypeInstance oper1 = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance oper2 = n.f2.accept(this, argu);
+	return (oper1.get_type() == TypeEnum.integer &&
+		oper2.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.integer) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "-"
+     * f2 -> PrimaryExpression()
+     */
+    public TypeInstance visit(MinusExpression n, HashMap<String,String> argu) {
+	TypeInstance oper1 = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance oper2 = n.f2.accept(this, argu);
+	return (oper1.get_type() == TypeEnum.integer &&
+		oper2.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.integer) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "*"
+     * f2 -> PrimaryExpression()
+     */
+    public TypeInstance visit(TimesExpression n, HashMap<String,String> argu) {
+	TypeInstance oper1 = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance oper2 = n.f2.accept(this, argu);
+	return (oper1.get_type() == TypeEnum.integer &&
+		oper2.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.integer) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "["
+     * f2 -> PrimaryExpression()
+     * f3 -> "]"
+     */
+    public TypeInstance visit(ArrayLookup n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	TypeInstance array = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	TypeInstance index = n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	return (array.get_type() == TypeEnum.int_array &&
+		index.get_type() == TypeEnum.integer) ?
+	    new TypeInstance(TypeEnum.integer) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "."
+     * f2 -> "length"
+     */
+    public TypeInstance visit(ArrayLength n, HashMap<String,String> argu) {
+	// can only act on an array
+	TypeInstance _ret=null;
+	TypeInstance ret = n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return (ret.get_type() == TypeEnum.int_array) ? new TypeInstance(TypeEnum.integer) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> PrimaryExpression()
+     * f1 -> "."
+     * f2 -> Identifier()
+     * f3 -> "("
+     * f4 -> ( ExpressionList() )?
+     * f5 -> ")"
+     */
+    public TypeInstance visit(MessageSend n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	n.f5.accept(this, argu);
+	return _ret;
+    }
+
+    // FIXME
+    /**
+     * f0 -> Expression()
+     * f1 -> ( ExpressionRest() )*
+     */
+    public TypeInstance visit(ExpressionList n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	n.f1.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> ","
+     * f1 -> Expression()
+     */
+    public TypeInstance visit(ExpressionRest n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	return ret;
+    }
+
+    /**
+     * f0 -> IntegerLiteral()
+     *               | TrueLiteral()
+     *               | FalseLiteral()
+     *               | Identifier()
+     *               | ThisExpression()
+     *               | ArrayAllocationExpression()
+     *               | AllocationExpression()
+     *               | NotExpression()
+     *               | BracketExpression()
+     */
+    public TypeInstance visit(PrimaryExpression n, HashMap<String,String> argu) {
+	return n.f0.accept(this, argu);
+    }
+
+    /**
+     * f0 -> <INTEGER_LITERAL>
+     */
+    public TypeInstance visit(IntegerLiteral n, HashMap<String,String> argu) {
+	return new TypeInstance(TypeEnum.integer);
+    }
+
+    /**
+     * f0 -> "true"
+     */
+    public TypeInstance visit(TrueLiteral n, HashMap<String,String> argu) {
+	return new TypeInstance(TypeEnum.bool);
+    }
+
+    /**
+     * f0 -> "false"
+     */
+    public TypeInstance visit(FalseLiteral n, HashMap<String,String> argu) {
+	return new TypeInstance(TypeEnum.bool);
+    }
+
+    /**
+     * f0 -> <IDENTIFIER>
+     */
+    public TypeInstance visit(Identifier n, HashMap<String,String> argu) {
+	return new TypeInstance(TypeEnum.CHECK);
+    }
+
+    //FIXME
+    /**
+     * f0 -> "this"
+     */
+    public TypeInstance visit(ThisExpression n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	return _ret;
+    }
+
+    /**
+     * f0 -> "new"
+     * f1 -> "int"
+     * f2 -> "["
+     * f3 -> Expression()
+     * f4 -> "]"
+     */
+    public TypeInstance visit(ArrayAllocationExpression n, HashMap<String,String> argu) {
+	TypeInstance _ret=null;
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	n.f4.accept(this, argu);
+	return (ret.get_type() == TypeEnum.integer) ? new TypeInstance(TypeEnum.int_array) :
+	    new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> "new"
+     * f1 -> Identifier()
+     * f2 -> "("
+     * f3 -> ")"
+     */
+    public TypeInstance visit(AllocationExpression n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	n.f3.accept(this, argu);
+	return ret;
+    }
+
+    /**
+     * f0 -> "!"
+     * f1 -> Expression()
+     */
+    public TypeInstance visit(NotExpression n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	return (ret.get_type() == TypeEnum.bool) ? ret : new TypeInstance(TypeEnum.ERROR);
+    }
+
+    /**
+     * f0 -> "("
+     * f1 -> Expression()
+     * f2 -> ")"
+     */
+    public TypeInstance visit(BracketExpression n, HashMap<String,String> argu) {
+	n.f0.accept(this, argu);
+	TypeInstance ret = n.f1.accept(this, argu);
+	n.f2.accept(this, argu);
+	return ret;
+    }
+
+}
diff --git a/minijava/TypeEnum.java b/minijava/TypeEnum.java
new file mode 100644
index 0000000..4003eba
--- /dev/null
+++ b/minijava/TypeEnum.java
@@ -0,0 +1,5 @@
+package minijava;
+
+public enum TypeEnum {
+	int_array, bool, integer, CHECK, ERROR
+}
diff --git a/minijava/TypeInstance.java b/minijava/TypeInstance.java
new file mode 100644
index 0000000..13920e4
--- /dev/null
+++ b/minijava/TypeInstance.java
@@ -0,0 +1,29 @@
+package minijava;
+
+public class TypeInstance {
+	TypeEnum type;
+
+	public TypeInstance(TypeEnum type) {
+		this.type = type;
+	}
+
+	public boolean equal_type(TypeInstance other) {
+		/**
+		 * Given a TypeInstance object other,
+		 * returns true if other object
+		 * is the same type as this one.
+		 *
+		 * We can say two types are equal, as
+		 * long as they are not equal on a
+		 * type error!
+		 */
+
+		return this.type != TypeEnum.ERROR
+			this.type == other.type;
+	}
+
+	public TypeEnum get_type() {
+		return this.type;
+	}
+
+}