Establish distributivity for type union & intersection

src/types.h

Index: src/types.h
diff --git a/src/types.h b/src/types.h
index 5ca3a81452c2fa3a10b789f3ed71b07630d96a75..245cf76435325dc1fd4770c9b7de2d6382a9d276 100644
--- a/src/types.h
+++ b/src/types.h
@@ -132,8 +132,8 @@ namespace internal {
   V(Representation, static_cast<int>(0xff800000)) \
   V(Semantic,       static_cast<int>(0x007fffff))
 
-#define REPRESENTATION(k) ((k) & kRepresentation)
-#define SEMANTIC(k)       ((k) & kSemantic)
+#define REPRESENTATION(k) ((k) & BitsetType::kRepresentation)
+#define SEMANTIC(k)       ((k) & BitsetType::kSemantic)
 
 #define REPRESENTATION_BITSET_TYPE_LIST(V) \
   V(None,             0)                   \
@@ -202,16 +202,13 @@ namespace internal {
 //   template<class T> static Handle<T>::type cast(Handle<Type>::type);
 //   static bool is_bitset(Type*);
 //   static bool is_class(Type*);
-//   static bool is_constant(Type*);
 //   static bool is_struct(Type*, int tag);
 //   static int as_bitset(Type*);
 //   static i::Handle<i::Map> as_class(Type*);
-//   static i::Handle<i::Object> as_constant(Type*);
 //   static Handle<Struct>::type as_struct(Type*);
 //   static Type* from_bitset(int bitset);
 //   static Handle<Type>::type from_bitset(int bitset, Region*);
-//   static Handle<Type>::type from_class(i::Handle<Map>, int lub, Region*);
-//   static Handle<Type>::type from_constant(i::Handle<Object>, int, Region*);
+//   static Handle<Type>::type from_class(i::Handle<Map>, Region*);
 //   static Handle<Type>::type from_struct(Handle<Struct>::type, int tag);
 //   static Handle<Struct>::type struct_create(int tag, int length, Region*);
 //   static void struct_shrink(Handle<Struct>::type, int length);
@@ -219,7 +216,10 @@ namespace internal {
 //   static int struct_length(Handle<Struct>::type);
 //   static Handle<Type>::type struct_get(Handle<Struct>::type, int);
 //   static void struct_set(Handle<Struct>::type, int, Handle<Type>::type);
-//   static int lub_bitset(Type*);
+//   template<class V>
+//   static i::Handle<V> struct_get_value(Handle<Struct>::type, int);
+//   template<class V>
+//   static void struct_set_value(Handle<Struct>::type, int, i::Handle<V>);
 // }
 template<class Config>
 class TypeImpl : public Config::Base {
@@ -289,9 +289,7 @@ class TypeImpl : public Config::Base {
     return Of(*value, region);
   }
 
-  bool IsInhabited() {
-    return !this->IsBitset() || BitsetType::IsInhabited(this->AsBitset());
-  }
+  bool IsInhabited() { return BitsetType::IsInhabited(this->BitsetLub()); }
 
   bool Is(TypeImpl* that) { return this == that || this->SlowIs(that); }
   template<class TypeHandle>
@@ -323,9 +321,16 @@ class TypeImpl : public Config::Base {
 
   bool NowStable();
 
-  bool IsClass() { return Config::is_class(this); }
-  bool IsConstant() { return Config::is_constant(this); }
-  bool IsArray() { return Config::is_struct(this, StructuralType::kArrayTag); }
+  bool IsClass() {
+    return Config::is_class(this)
+        || Config::is_struct(this, StructuralType::kClassTag);
+  }
+  bool IsConstant() {
+    return Config::is_struct(this, StructuralType::kConstantTag);
+  }
+  bool IsArray() {
+    return Config::is_struct(this, StructuralType::kArrayTag);
+  }
   bool IsFunction() {
     return Config::is_struct(this, StructuralType::kFunctionTag);
   }
@@ -366,6 +371,7 @@ class TypeImpl : public Config::Base {
   static typename Config::template Handle<T>::type handle(T* type) {
     return Config::handle(type);
   }
+  TypeImpl* unhandle() { return this; }
 
   bool IsNone() { return this == None(); }
   bool IsAny() { return this == Any(); }
@@ -380,14 +386,17 @@ class TypeImpl : public Config::Base {
 
   bool SlowIs(TypeImpl* that);
 
-  bool InUnion(UnionHandle unioned, int current_size);
+  TypeHandle Narrow(int bitset, Region* region);
+  int BoundBy(TypeImpl* that);
+  int IndexInUnion(int bound, UnionHandle unioned, int current_size);
   static int ExtendUnion(
-      UnionHandle unioned, TypeHandle t, int current_size);
-  static int ExtendIntersection(
-      UnionHandle unioned, TypeHandle t, TypeHandle other, int current_size);
+      UnionHandle unioned, int current_size, TypeHandle t,
+      TypeHandle other, bool is_intersect, Region* region);
+  static int NormalizeUnion(UnionHandle unioned, int current_size, int bitset);
 
   int BitsetGlb() { return BitsetType::Glb(this); }
   int BitsetLub() { return BitsetType::Lub(this); }
+  int InherentBitsetLub() { return BitsetType::InherentLub(this); }
 };
 
 
@@ -405,7 +414,7 @@ class TypeImpl<Config>::BitsetType : public TypeImpl<Config> {
 
   int Bitset() { return Config::as_bitset(this); }
 
-  static BitsetType* New(int bitset) {
+  static TypeImpl* New(int bitset) {
     return static_cast<BitsetType*>(Config::from_bitset(bitset));
   }
   static TypeHandle New(int bitset, Region* region) {
@@ -420,6 +429,7 @@ class TypeImpl<Config>::BitsetType : public TypeImpl<Config> {
   static int Lub(TypeImpl* type);  // least upper bound that's a bitset
   static int Lub(i::Object* value);
   static int Lub(i::Map* map);
+  static int InherentLub(TypeImpl* type);
 
   static const char* Name(int bitset);
   static void BitsetTypePrint(FILE* out, int bitset);
@@ -447,29 +457,88 @@ class TypeImpl<Config>::StructuralType : public TypeImpl<Config> {
     return Config::struct_length(Config::as_struct(this));
   }
   TypeHandle Get(int i) {
+    ASSERT(0 <= i && i < this->Length());
     return Config::struct_get(Config::as_struct(this), i);
   }
   void Set(int i, TypeHandle type) {
+    ASSERT(0 <= i && i < this->Length());
     Config::struct_set(Config::as_struct(this), i, type);
   }
   void Shrink(int length) {
+    ASSERT(2 <= length && length <= this->Length());
     Config::struct_shrink(Config::as_struct(this), length);
   }
+  template<class V> i::Handle<V> GetValue(int i) {
+    ASSERT(0 <= i && i < this->Length());
+    return Config::template struct_get_value<V>(Config::as_struct(this), i);
+  }
+  template<class V> void SetValue(int i, i::Handle<V> x) {
+    ASSERT(0 <= i && i < this->Length());
+    Config::struct_set_value(Config::as_struct(this), i, x);
+  }
 
   static TypeHandle New(Tag tag, int length, Region* region) {
+    ASSERT(1 <= length);
     return Config::from_struct(Config::struct_create(tag, length, region));
   }
 };
 
 
+// Internal
+// A union is a structured type with the following invariants:
+// - its length is at least 2
+// - at most one field is a bitset, and it must go into index 0
+// - no field is a union
+// - no field is a subtype of any other field
 template<class Config>
-class TypeImpl<Config>::ClassType : public TypeImpl<Config> {
+class TypeImpl<Config>::UnionType : public StructuralType {
  public:
-  i::Handle<i::Map> Map() { return Config::as_class(this); }
+  static UnionHandle New(int length, Region* region) {
+    return Config::template cast<UnionType>(
+        StructuralType::New(StructuralType::kUnionTag, length, region));
+  }
+
+  static UnionType* cast(TypeImpl* type) {
+    ASSERT(type->IsUnion());
+    return static_cast<UnionType*>(type);
+  }
+
+  bool Wellformed();
+};
+
+
+template<class Config>
+class TypeImpl<Config>::ClassType : public StructuralType {
+ public:
+  TypeHandle Bound(Region* region) {
+    return Config::is_class(this)
+        ? BitsetType::New(BitsetType::Lub(*Config::as_class(this)), region)
+        : this->Get(0);
+  }
+  i::Handle<i::Map> Map() {
+    return Config::is_class(this)
+        ? Config::as_class(this)
+        : this->template GetValue<i::Map>(1);
+  }
+
+  static ClassHandle New(
+      i::Handle<i::Map> map, TypeHandle bound, Region* region) {
+    ClassHandle type = Config::template cast<ClassType>(
+        StructuralType::New(StructuralType::kClassTag, 2, region));
+    type->Set(0, bound);
+    type->SetValue(1, map);
+    return type;
+  }
 
   static ClassHandle New(i::Handle<i::Map> map, Region* region) {
-    return Config::template cast<ClassType>(
-        Config::from_class(map, BitsetType::Lub(*map), region));
+    ClassHandle type =
+        Config::template cast<ClassType>(Config::from_class(map, region));
+    if (type->IsClass()) {
+      return type;
+    } else {
+      TypeHandle bound = BitsetType::New(BitsetType::Lub(*map), region);
+      return New(map, bound, region);
+    }
   }
 
   static ClassType* cast(TypeImpl* type) {
@@ -480,13 +549,23 @@ class TypeImpl<Config>::ClassType : public TypeImpl<Config> {
 
 
 template<class Config>
-class TypeImpl<Config>::ConstantType : public TypeImpl<Config> {
+class TypeImpl<Config>::ConstantType : public StructuralType {
  public:
-  i::Handle<i::Object> Value() { return Config::as_constant(this); }
+  TypeHandle Bound() { return this->Get(0); }
+  i::Handle<i::Object> Value() { return this->template GetValue<i::Object>(1); }
+
+  static ConstantHandle New(
+      i::Handle<i::Object> value, TypeHandle bound, Region* region) {
+    ConstantHandle type = Config::template cast<ConstantType>(
+        StructuralType::New(StructuralType::kConstantTag, 2, region));
+    type->Set(0, bound);
+    type->SetValue(1, value);
+    return type;
+  }
 
   static ConstantHandle New(i::Handle<i::Object> value, Region* region) {
-    return Config::template cast<ConstantType>(
-        Config::from_constant(value, BitsetType::Lub(*value), region));
+    TypeHandle bound = BitsetType::New(BitsetType::Lub(*value), region);
+    return New(value, bound, region);
   }
 
   static ConstantType* cast(TypeImpl* type) {
@@ -496,38 +575,26 @@ class TypeImpl<Config>::ConstantType : public TypeImpl<Config> {
 };
 
 
-// Internal
-// A union is a structured type with the following invariants:
-// - its length is at least 2
-// - at most one field is a bitset, and it must go into index 0
-// - no field is a union
-template<class Config>
-class TypeImpl<Config>::UnionType : public StructuralType {
- public:
-  static UnionHandle New(int length, Region* region) {
-    return Config::template cast<UnionType>(
-        StructuralType::New(StructuralType::kUnionTag, length, region));
-  }
-
-  static UnionType* cast(TypeImpl* type) {
-    ASSERT(type->IsUnion());
-    return static_cast<UnionType*>(type);
-  }
-};
-
-
 template<class Config>
 class TypeImpl<Config>::ArrayType : public StructuralType {
  public:
-  TypeHandle Element() { return this->Get(0); }
+  TypeHandle Bound() { return this->Get(0); }
+  TypeHandle Element() { return this->Get(1); }
 
-  static ArrayHandle New(TypeHandle element, Region* region) {
+  static ArrayHandle New(TypeHandle element, TypeHandle bound, Region* region) {
+    ASSERT(SEMANTIC(bound->AsBitset()) == SEMANTIC(BitsetType::kArray));
     ArrayHandle type = Config::template cast<ArrayType>(
-        StructuralType::New(StructuralType::kArrayTag, 1, region));
-    type->Set(0, element);
+        StructuralType::New(StructuralType::kArrayTag, 2, region));
+    type->Set(0, bound);
+    type->Set(1, element);
     return type;
   }
 
+  static ArrayHandle New(TypeHandle element, Region* region) {
+    TypeHandle bound = BitsetType::New(BitsetType::kArray, region);
+    return New(element, bound, region);
+  }
+
   static ArrayType* cast(TypeImpl* type) {
     ASSERT(type->IsArray());
     return static_cast<ArrayType*>(type);
@@ -538,22 +605,32 @@ class TypeImpl<Config>::ArrayType : public StructuralType {
 template<class Config>
 class TypeImpl<Config>::FunctionType : public StructuralType {
  public:
-  int Arity() { return this->Length() - 2; }
-  TypeHandle Result() { return this->Get(0); }
-  TypeHandle Receiver() { return this->Get(1); }
-  TypeHandle Parameter(int i) { return this->Get(2 + i); }
+  int Arity() { return this->Length() - 3; }
+  TypeHandle Bound() { return this->Get(0); }
+  TypeHandle Result() { return this->Get(1); }
+  TypeHandle Receiver() { return this->Get(2); }
+  TypeHandle Parameter(int i) { return this->Get(3 + i); }
 
-  void InitParameter(int i, TypeHandle type) { this->Set(2 + i, type); }
+  void InitParameter(int i, TypeHandle type) { this->Set(3 + i, type); }
 
   static FunctionHandle New(
-      TypeHandle result, TypeHandle receiver, int arity, Region* region) {
+      TypeHandle result, TypeHandle receiver, TypeHandle bound,
+      int arity, Region* region) {
+    ASSERT(SEMANTIC(bound->AsBitset()) == SEMANTIC(BitsetType::kFunction));
     FunctionHandle type = Config::template cast<FunctionType>(
-        StructuralType::New(StructuralType::kFunctionTag, 2 + arity, region));
-    type->Set(0, result);
-    type->Set(1, receiver);
+        StructuralType::New(StructuralType::kFunctionTag, 3 + arity, region));
+    type->Set(0, bound);
+    type->Set(1, result);
+    type->Set(2, receiver);
     return type;
   }
 
+  static FunctionHandle New(
+      TypeHandle result, TypeHandle receiver, int arity, Region* region) {
+    TypeHandle bound = BitsetType::New(BitsetType::kFunction, region);
+    return New(result, receiver, bound, arity, region);
+  }
+
   static FunctionType* cast(TypeImpl* type) {
     ASSERT(type->IsFunction());
     return static_cast<FunctionType*>(type);
@@ -598,29 +675,27 @@ struct ZoneTypeConfig {
 
   static inline bool is_bitset(Type* type);
   static inline bool is_class(Type* type);
-  static inline bool is_constant(Type* type);
   static inline bool is_struct(Type* type, int tag);
 
   static inline int as_bitset(Type* type);
-  static inline Struct* as_struct(Type* type);
   static inline i::Handle<i::Map> as_class(Type* type);
-  static inline i::Handle<i::Object> as_constant(Type* type);
+  static inline Struct* as_struct(Type* type);
 
   static inline Type* from_bitset(int bitset);
   static inline Type* from_bitset(int bitset, Zone* zone);
+  static inline Type* from_class(i::Handle<i::Map> map, Zone* zone);
   static inline Type* from_struct(Struct* structured);
-  static inline Type* from_class(i::Handle<i::Map> map, int lub, Zone* zone);
-  static inline Type* from_constant(
-      i::Handle<i::Object> value, int lub, Zone* zone);
 
   static inline Struct* struct_create(int tag, int length, Zone* zone);
-  static inline void struct_shrink(Struct* structured, int length);
-  static inline int struct_tag(Struct* structured);
-  static inline int struct_length(Struct* structured);
-  static inline Type* struct_get(Struct* structured, int i);
-  static inline void struct_set(Struct* structured, int i, Type* type);
-
-  static inline int lub_bitset(Type* type);
+  static inline void struct_shrink(Struct* structure, int length);
+  static inline int struct_tag(Struct* structure);
+  static inline int struct_length(Struct* structure);
+  static inline Type* struct_get(Struct* structure, int i);
+  static inline void struct_set(Struct* structure, int i, Type* type);
+  template<class V>
+  static inline i::Handle<V> struct_get_value(Struct* structure, int i);
+  template<class V> static inline void struct_set_value(
+      Struct* structure, int i, i::Handle<V> x);
 };
 
 typedef TypeImpl<ZoneTypeConfig> Type;
@@ -640,32 +715,32 @@ struct HeapTypeConfig {
 
   static inline bool is_bitset(Type* type);
   static inline bool is_class(Type* type);
-  static inline bool is_constant(Type* type);
   static inline bool is_struct(Type* type, int tag);
 
   static inline int as_bitset(Type* type);
   static inline i::Handle<i::Map> as_class(Type* type);
-  static inline i::Handle<i::Object> as_constant(Type* type);
   static inline i::Handle<Struct> as_struct(Type* type);
 
   static inline Type* from_bitset(int bitset);
   static inline i::Handle<Type> from_bitset(int bitset, Isolate* isolate);
   static inline i::Handle<Type> from_class(
-      i::Handle<i::Map> map, int lub, Isolate* isolate);
-  static inline i::Handle<Type> from_constant(
-      i::Handle<i::Object> value, int lub, Isolate* isolate);
-  static inline i::Handle<Type> from_struct(i::Handle<Struct> structured);
+      i::Handle<i::Map> map, Isolate* isolate);
+  static inline i::Handle<Type> from_struct(i::Handle<Struct> structure);
 
   static inline i::Handle<Struct> struct_create(
       int tag, int length, Isolate* isolate);
-  static inline void struct_shrink(i::Handle<Struct> structured, int length);
-  static inline int struct_tag(i::Handle<Struct> structured);
-  static inline int struct_length(i::Handle<Struct> structured);
-  static inline i::Handle<Type> struct_get(i::Handle<Struct> structured, int i);
+  static inline void struct_shrink(i::Handle<Struct> structure, int length);
+  static inline int struct_tag(i::Handle<Struct> structure);
+  static inline int struct_length(i::Handle<Struct> structure);
+  static inline i::Handle<Type> struct_get(i::Handle<Struct> structure, int i);
   static inline void struct_set(
-      i::Handle<Struct> structured, int i, i::Handle<Type> type);
-
-  static inline int lub_bitset(Type* type);
+      i::Handle<Struct> structure, int i, i::Handle<Type> type);
+  template<class V>
+  static inline i::Handle<V> struct_get_value(
+      i::Handle<Struct> structure, int i);
+  template<class V>
+  static inline void struct_set_value(
+      i::Handle<Struct> structure, int i, i::Handle<V> x);
 };
 
 typedef TypeImpl<HeapTypeConfig> HeapType;