diff --git a/src/TypeInference/Analyzer.cs b/src/TypeInference/Analyzer.cs
index 783ba1c..64a2f1e 100644
--- a/src/TypeInference/Analyzer.cs
+++ b/src/TypeInference/Analyzer.cs
@@ -13,7 +13,7 @@ public interface Analyzer
     {
         IFileSystem FileSystem { get; }
 
-        DataType loadFile(string path);
+        DataType LoadFile(string path);
         DataType loadModule(List<Name> name, State state);
         Module getAstForFile(string file);
         string moduleQname(string file);
@@ -365,7 +365,7 @@ public void putProblem(string file, int begin, int end, String msg)
         }
 
 
-        void addFileErr(String file, int begin, int end, String msg)
+        void addFileErr(string file, int begin, int end, String msg)
         {
             Diagnostic d = new Diagnostic(file, Diagnostic.Category.ERROR, begin, end, msg);
             getFileErrs(file, semanticErrors).Add(d);
@@ -383,7 +383,7 @@ List<Diagnostic> getFileErrs(string file, Dictionary<string, List<Diagnostic>> m
             return msgs;
         }
 
-        public DataType loadFile(string path)
+        public DataType LoadFile(string path)
         {
             path = FileSystem.GetFullPath(path);
 
@@ -405,7 +405,7 @@ public DataType loadFile(string path)
             }
 
             // set new CWD and save the old one on stack
-            String oldcwd = cwd;
+            string oldcwd = cwd;
             setCWD(FileSystem.GetDirectoryName(path));
 
             pushImportStack(path);
@@ -563,7 +563,7 @@ public DataType loadModule(List<Name> name, State state)
                 string initFile = FileSystem.CombinePath(path, "__init__.py");
                 if (FileSystem.FileExists(initFile))
                 {
-                    DataType mod = loadFile(initFile);
+                    DataType mod = LoadFile(initFile);
                     if (mod == null)
                     {
                         return null;
@@ -586,7 +586,7 @@ public DataType loadModule(List<Name> name, State state)
                     string startFile = path + suffix;
                     if (FileSystem.FileExists( startFile))
                     {
-                        DataType mod = loadFile(startFile);
+                        DataType mod = LoadFile(startFile);
                         if (mod == null)
                         {
                             return null;
@@ -636,7 +636,7 @@ public void loadFileRecursive(string fullname)
             {
                 if (file_or_dir.EndsWith(suffix))
                 {
-                    loadFile(file_or_dir);
+                    LoadFile(file_or_dir);
                 }
             }
         }
diff --git a/src/TypeInference/Binding.cs b/src/TypeInference/Binding.cs
index fda8e55..02e4912 100644
--- a/src/TypeInference/Binding.cs
+++ b/src/TypeInference/Binding.cs
@@ -7,7 +7,7 @@
 
 namespace Pytocs.TypeInference
 {
-    public class Binding : IComparable<object>
+    public class Binding : IComparable<Binding>
     {
         public enum Kind
         {
@@ -193,9 +193,9 @@ public bool isURL()
         /// <summary>
         /// Bindings can be sorted by their location for outlining purposes.
         /// </summary>
-        public int CompareTo(object o)
+        public int CompareTo(Binding o)
         {
-            return start - ((Binding) o).start;
+            return start - o.start;
         }
 
         public override string ToString()
@@ -207,17 +207,14 @@ public override string ToString()
             sb.Append(":type=").Append(type);
             sb.Append(":qname=").Append(qname);
             sb.Append(":refs=");
+            sb.Append("[");
             if (refs.Count > 10)
             {
-                sb.Append("[");
                 sb.Append(refs.First());
-                sb.Append(", ...(");
-                sb.Append(refs.Count - 1);
-                sb.Append(" more)]");
+                sb.AppendFormat(", ...({0} more)]", refs.Count - 1);
             }
             else
             {
-                sb.Append("[");
                 var sep = "";
                 foreach (var r in refs)
                 {
diff --git a/src/TypeInference/Builtins.cs b/src/TypeInference/Builtins.cs
index e5f6dd2..e999df3 100644
--- a/src/TypeInference/Builtins.cs
+++ b/src/TypeInference/Builtins.cs
@@ -90,7 +90,7 @@ public static Url newTutUrl(string path)
             "UnicodeEncodeError", "UnicodeError", "UnicodeTranslateError",
             "UnicodeWarning", "UserWarning", "ValueError", "Warning",
             "ZeroDivisionError"
-    };
+        };
 
         ClassType newClass(string name, State table)
         {
diff --git a/src/TypeInference/ILogger.cs b/src/TypeInference/ILogger.cs
index 7828201..41843f9 100644
--- a/src/TypeInference/ILogger.cs
+++ b/src/TypeInference/ILogger.cs
@@ -14,7 +14,6 @@ public interface ILogger
         void Error(Exception ex, string p);
         void Inform(string p);
         void Verbose(string p);
-
     }
 
     public class Logger : ILogger
diff --git a/src/TypeInference/Options.cs b/src/TypeInference/Options.cs
index d62b0e2..5bddf47 100644
--- a/src/TypeInference/Options.cs
+++ b/src/TypeInference/Options.cs
@@ -3,13 +3,11 @@
 
 namespace org.yinwang.pysonar
 {
-
     public class Options
     {
         private Dictionary<string, object> optionsMap = new Dictionary<string, object>();
         private List<string> args = new List<string>();
 
-
         public Options(params string[] args)
         {
             for (int i = 0; i < args.Length; i++)
diff --git a/src/TypeInference/Progress.cs b/src/TypeInference/Progress.cs
index 91b9627..158bc42 100644
--- a/src/TypeInference/Progress.cs
+++ b/src/TypeInference/Progress.cs
@@ -7,16 +7,16 @@ public class Progress
         private const int MAX_SPEED_DIGITS = 5;
 
         private Analyzer analyzer;
-        DateTime startTime;
-        DateTime lastTickTime;
-        long lastCount;
-        int lastRate;
-        int lastAvgRate;
-        long total;
-        long count;
-        long width;
-        long segSize;
-        bool quiet;
+        private DateTime startTime;
+        private DateTime lastTickTime;
+        private long lastCount;
+        private int lastRate;
+        private int lastAvgRate;
+        private long total;
+        private long count;
+        private long width;
+        private long segSize;
+        private bool quiet;
 
         public Progress(Analyzer analyzer, long total, long width, bool quiet)
         {
diff --git a/src/TypeInference/State.cs b/src/TypeInference/State.cs
index fc5f8c6..0f07e7c 100644
--- a/src/TypeInference/State.cs
+++ b/src/TypeInference/State.cs
@@ -57,7 +57,7 @@ public State(State s)
         }
 
         // erase and overwrite this to s's contents
-        public void overwrite(State s)
+        public void Overwrite(State s)
         {
             this.table = s.table;
             this.Parent = s.Parent;
@@ -310,9 +310,9 @@ public ISet<Binding> lookupAttr(string attr)
         }
 
 
-        /**
-         * Look for a binding named {@code name} and if found, return its type.
-         */
+        /// <summary>
+        /// Look for a binding named {@code name} and if found, return its type.
+        /// </summary>
         public DataType lookupType(string name)
         {
             ISet<Binding> bs = lookup(name);
diff --git a/src/TypeInference/Statistics.cs b/src/TypeInference/Statistics.cs
index 260a46d..da8876a 100644
--- a/src/TypeInference/Statistics.cs
+++ b/src/TypeInference/Statistics.cs
@@ -6,25 +6,17 @@ namespace Pytocs.TypeInference
 {
     public class Statistics
     {
-        IDictionary<string, object> contents = new Dictionary<string, object>();
+        IDictionary<string, long> contents = new Dictionary<string, long>();
 
         public void putInt(string key, long value)
         {
             contents[key] = value;
         }
 
-
         public void inc(string key, long x)
         {
-            long? old = getInt(key);
-            if (!old.HasValue)
-            {
-                contents[key] = 1;
-            }
-            else
-            {
-                contents[key] = old.Value + x;
-            }
+            long old = getInt(key);
+            contents[key] = old + x;
         }
 
         public void inc(string key)
@@ -34,35 +26,21 @@ public void inc(string key)
 
         public long getInt(string key)
         {
-            object ret;
+            long ret;
             if (!contents.TryGetValue(key, out ret))
                 return 0;
-            return (long) ret;
+            return ret;
         }
 
-
         public string print()
         {
             StringBuilder sb = new StringBuilder();
-
             foreach (var e in contents)
             {
-                sb.AppendFormat("\n- {0}: {1}", e.Key, e.Value);
+                sb.AppendLine();
+                sb.AppendFormat("- {0}: {1}", e.Key, e.Value);
             }
             return sb.ToString();
         }
-
-        internal void putDate(string key, DateTime dateTime)
-        {
-            contents[key] = dateTime;
-        }
-
-        internal DateTime getDateTime(string key)
-        {
-            object dt;
-            if (contents.TryGetValue(key, out dt))
-                return (DateTime) dt;
-            return default(DateTime);
-        }
     }
 }
\ No newline at end of file
diff --git a/src/TypeInference/TypeStack.cs b/src/TypeInference/TypeStack.cs
index ac1c878..222d4f2 100644
--- a/src/TypeInference/TypeStack.cs
+++ b/src/TypeInference/TypeStack.cs
@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System;
+using Pytocs.Types;
 
 namespace Pytocs.TypeInference
 {
@@ -7,10 +8,10 @@ public class TypeStack
     {
         class Pair
         {
-            public object first;
-            public object second;
+            public DataType first;
+            public DataType second;
 
-            public Pair(object first, object second)
+            public Pair(DataType first, DataType second)
             {
                 this.first = first;
                 this.second = second;
@@ -19,7 +20,7 @@ public Pair(object first, object second)
 
         private List<Pair> stack = new List<Pair>();
 
-        public void push(object first, object second)
+        public void push(DataType first, DataType second)
         {
             stack.Add(new Pair(first, second));
         }
@@ -29,12 +30,14 @@ public void pop(object first, object second)
             stack.RemoveAt(stack.Count - 1);
         }
 
-        public bool contains(object first, object second)
+        public bool contains(DataType first, DataType second)
         {
             foreach (Pair p in stack)
             {
-                if (p.first == first && p.second == second ||
-                        p.first == second && p.second == first)
+                if (object.ReferenceEquals(p.first, first) && 
+                    object.ReferenceEquals(p.second, second) ||
+                    object.ReferenceEquals(p.first, second) &&
+                    object.ReferenceEquals(p.second, first))
                 {
                     return true;
                 }
diff --git a/src/TypeInference/TypeTransformer.cs b/src/TypeInference/TypeTransformer.cs
index deca152..256692c 100644
--- a/src/TypeInference/TypeTransformer.cs
+++ b/src/TypeInference/TypeTransformer.cs
@@ -11,7 +11,7 @@ public class TypeTransformer : // INodeVisitor<DataType>,
         IExpVisitor<DataType>
     {
         private State scope;
-        public Analyzer analyzer;
+        private Analyzer analyzer;
 
         public TypeTransformer(State s, Analyzer analyzer)
         {
@@ -812,15 +812,15 @@ public DataType VisitIf(IfStatement i)
             if (cont1 && cont2)
             {
                 s1.merge(s2);
-                scope.overwrite(s1);
+                scope.Overwrite(s1);
             }
             else if (cont1)
             {
-                scope.overwrite(s1);
+                scope.Overwrite(s1);
             }
             else if (cont2)
             {
-                scope.overwrite(s2);
+                scope.Overwrite(s2);
             }
             return UnionType.union(type1, type2);
         }
diff --git a/src/Types/DictType.cs b/src/Types/DictType.cs
index 2371e93..35f55f9 100644
--- a/src/Types/DictType.cs
+++ b/src/Types/DictType.cs
@@ -36,13 +36,16 @@ public TupleType toTupleType(int n)
 
         public override bool Equals(object other)
         {
-            if (typeStack.contains(this, other))
+            var dtOther = other as DataType;
+            if (dtOther == null)
+                return false;
+            if (typeStack.contains(this, dtOther))
             {
                 return true;
             }
             else if (other is DictType)
             {
-                typeStack.push(this, other);
+                typeStack.push(this, dtOther);
                 DictType co = (DictType) other;
                 bool ret = (co.keyType.Equals(keyType) &&
                         co.valueType.Equals(valueType));
diff --git a/src/Types/FloatType.cs b/src/Types/FloatType.cs
index 8027b99..2675579 100644
--- a/src/Types/FloatType.cs
+++ b/src/Types/FloatType.cs
@@ -14,7 +14,7 @@ public override bool Equals(object other)
 
         public override int GetHashCode()
         {
-            return "FloatType".GetHashCode();
+            return GetType().Name.GetHashCode();
         }
     }
 }
\ No newline at end of file
diff --git a/src/Types/ListType.cs b/src/Types/ListType.cs
index eb0114e..566a164 100644
--- a/src/Types/ListType.cs
+++ b/src/Types/ListType.cs
@@ -66,14 +66,17 @@ public TupleType toTupleType()
 
         public override bool Equals(object other)
         {
-            if (typeStack.contains(this, other))
+            var dtOther = other as DataType;
+            if (dtOther == null)
+                return false;
+            if (typeStack.contains(this, dtOther))
             {
                 return true;
             }
             else if (other is ListType)
             {
                 ListType co = (ListType) other;
-                typeStack.push(this, other);
+                typeStack.push(this, co);
                 bool ret = co.eltType.Equals(eltType);
                 typeStack.pop(this, other);
                 return ret;
diff --git a/src/Types/TupleType.cs b/src/Types/TupleType.cs
index 43490ec..b76de7a 100644
--- a/src/Types/TupleType.cs
+++ b/src/Types/TupleType.cs
@@ -71,7 +71,10 @@ public ListType toListType()
 
         public override bool Equals(object other)
         {
-            if (typeStack.contains(this, other))
+            var dtOther = other as DataType;
+            if (dtOther == null)
+                return false;
+            if (typeStack.contains(this, dtOther))
             {
                 return true;
             }
@@ -82,7 +85,7 @@ public override bool Equals(object other)
 
                 if (types1.Count != types2.Count)
                     return false;
-                typeStack.push(this, other);
+                typeStack.push(this, dtOther);
                 for (int i = 0; i < types1.Count; i++)
                 {
                     if (!types1[i].Equals(types2[i]))
diff --git a/src/Types/UnionType.cs b/src/Types/UnionType.cs
index f8b09e8..e69a042 100644
--- a/src/Types/UnionType.cs
+++ b/src/Types/UnionType.cs
@@ -148,7 +148,10 @@ public DataType firstUseful()
 
         public override bool Equals(object other)
         {
-            if (typeStack.contains(this, other))
+            var dtOther = other as DataType;
+            if (dtOther == null)
+                return false;
+            if (typeStack.contains(this, dtOther))
             {
                 return true;
             }
@@ -162,7 +165,7 @@ public override bool Equals(object other)
                 }
                 else
                 {
-                    typeStack.push(this, other);
+                    typeStack.push(this, dtOther);
                     foreach (DataType t in types2)
                     {
                         if (!types1.Contains(t))