13.3 Calling Superclass Methods

1 files changed, 27 insertions, 1 deletions

diff --git a/src/com/craftinginterpreters/lox/Interpreter.java b/src/com/craftinginterpreters/lox/Interpreter.java
index 101c33c..3f4d385 100644
--- a/src/com/craftinginterpreters/lox/Interpreter.java
+++ b/src/com/craftinginterpreters/lox/Interpreter.java
@@ -63,6 +63,22 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
     }
 
     @Override
+    public Object visitSuperExpr(Expr.Super expr) {
+        int distance = locals.get(expr);
+        LoxClass superclass = (LoxClass) environment.getAt(distance, "super");
+
+        LoxInstance object = (LoxInstance) environment.getAt(distance - 1, "this");
+
+        LoxFunction method = superclass.findMethod(expr.method.lexeme);
+
+        if (method == null) {
+            throw new RuntimeError(expr.method, "Undefined property '" + expr.method.lexeme + "'.");
+        }
+
+        return method.bind(object);
+    }
+
+    @Override
     public Object visitThisExpr(Expr.This expr) {
         return lookUpVariable(expr.keyword, expr);
     }
@@ -190,13 +206,23 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
         }
         environment.define(stmt.name.lexeme, null);
 
+        if (stmt.superclass != null) {
+            environment = new Environment(environment);
+            environment.define("super", superclass);
+        }
+
         Map<String, LoxFunction> methods = new HashMap<>();
         for (Stmt.Function method : stmt.methods) {
             LoxFunction function = new LoxFunction(method, environment, method.name.lexeme.equals("init"));
             methods.put(method.name.lexeme, function);
         }
 
-        LoxClass klass = new LoxClass(stmt.name.lexeme, (LoxClass)superclass, methods);
+        LoxClass klass = new LoxClass(stmt.name.lexeme, (LoxClass) superclass, methods);
+
+        if (superclass != null) {
+            environment = environment.enclosing;
+        }
+
         environment.assign(stmt.name, klass);
         return null;
     }