Added expression statement

src/Statement.cpp

@@ -1,10 +1,24 @@
 #include "Statement.h"
 
-Statement::Statement(Kind kind): kind(kind) {
+Statement::Statement(Kind kind, Token token, shared_ptr<Expression> expression): kind(kind), token(token), expression(expression) {
+}
+
+shared_ptr<Expression> Statement::getExpression() {
+    return expression;
+}
+
+Token Statement::getToken() {
+    return token;
+}
+
+bool Statement::isValid() {
+    return kind != Statement::Kind::INVALID;
 }
 
 string Statement::toString() {
     switch (kind) {
+        case EXPRESSION:
+            return expression->toString();
         case INVALID:
             return "INVALID";
     }