1 files changed, 39 insertions, 18 deletions
diff --git a/st/SymbolTable.java b/st/SymbolTable.java
index fa6bdf2..ca38295 100644
--- a/st/SymbolTable.java
+++ b/st/SymbolTable.java
@@ -56,27 +56,48 @@ public class SymbolTable {
                                          cls.getName(),
                                          ext.getName()));
         cls.setExtend(ext);
+        TokenKey k;
         for (TypeInstance t : ext.getLocals()) {
-            MinimalLogger.info(String.format("Added %s (%s) as a local var of %s (%s)",
-                                             t.getName(), t.getType(),
-                                             cls.getName(), cls.getType()));
-            cls.addLocal(t);
-            this.symt.put(new TokenKey(t.getName(),
-                                       TypeEnum.integer,
-                                       cls,
-                                       null),
-                          t);
+            k = new TokenKey(t.getName(), TypeEnum.integer,
+                             cls, null);
+            if (this.symt.get(k) == null) {
+                MinimalLogger.info(String.format("Added %s (%s) as a local var of %s (%s)",
+                                                 t.getName(), t.getType(),
+                                                 cls.getName(), cls.getType()));
+                cls.addLocal(t);
+                this.symt.put(k, t);
+            } else { MinimalLogger.info(String.format("%s found to be overridden in %s.",
+                                                      t.getName(), cls.getName())); }
         }
         for (MethodInstance m : ext.getMethods()) {
-            MinimalLogger.info(String.format("Added %s (%s) as a method of %s (%s)",
-                                             m.getName(), m.getType(),
-                                             cls.getName(), cls.getType()));
-            this.symt.put(new TokenKey(m.getName(),
-                                       TypeEnum.method,
-                                       cls,
-                                       null),
-                          m);
-            cls.addMethod(m);
+            k = new TokenKey(m.getName(), TypeEnum.method,
+                             cls, null);
+            if (this.symt.get(k) == null) {
+                MinimalLogger.info(String.format("Added %s (%s) as a method of %s (%s)",
+                                                 m.getName(), m.getType(),
+                                                 cls.getName(), cls.getType()));
+                this.symt.put(k, m);
+                cls.addMethod(m);
+            } else {
+                MethodInstance exist = (MethodInstance) this.symt.get(k);
+                ArrayList<TypeInstance> expected = exist.getArguments();
+                ArrayList<TypeInstance> actual = m.getArguments();
+                if (expected.size() != actual.size() ||
+                    !exist.getReturn().equals(m.getReturn()))
+                    throw new TypecheckException(String.format("SymbolTable found that %s is overwritten in %s!",
+                                                               m.getName(),
+                                                               cls.getName()));
+                for (int i = 0; i < actual.size(); ++i) {
+                    if (expected.get(i).getClassInstance() != actual.get(i).getClassInstance()) {
+                        throw new TypecheckException(String.format("SymbolTable found that %s is overwritten in %s!",
+                                                                   m.getName(),
+                                                                   cls.getName()));
+                    }
+                }
+
+                MinimalLogger.info(String.format("%s found to be overridden in %s.",
+                                                 m.getName(), cls.getName()));
+            }
         }
     }