New unified type representation

test/cctest/test-types.cc

Index: test/cctest/test-types.cc
diff --git a/test/cctest/test-types.cc b/test/cctest/test-types.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d5852e0c0ff1feafcdeeafeb86f08da9d29523b4
--- /dev/null
+++ b/test/cctest/test-types.cc
@@ -0,0 +1,521 @@
+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "cctest.h"
+#include "types.h"
+
+using namespace v8::internal;
+
+// Testing auxiliaries (breaking the Type abstraction).
+static bool IsBitset(Type* type) { return type->IsSmi(); }
+static bool IsClass(Type* type) { return type->IsMap(); }
+static bool IsUnion(Type* type) { return type->IsFixedArray(); }
+static bool IsConstant(Type* type) {
+  return !(IsBitset(type) || IsClass(type) || IsUnion(type));
+}
+
+static int AsBitset(Type* type) { return Smi::cast(type)->value(); }
+static Map* AsClass(Type* type) { return Map::cast(type); }
+static HeapObject* AsConstant(Type* type) { return HeapObject::cast(type); }
+static FixedArray* AsUnion(Type* type) { return FixedArray::cast(type); }
+
+class HandlifiedTypes {
+ public:
+  explicit HandlifiedTypes(Isolate* isolate) :
+      None(Type::None(), isolate),
+      Any(Type::Any(), isolate),
+      Oddball(Type::Oddball(), isolate),
+      Boolean(Type::Boolean(), isolate),
+      Null(Type::Null(), isolate),
+      Undefined(Type::Undefined(), isolate),
+      Number(Type::Number(), isolate),
+      Smi(Type::Smi(), isolate),
+      Double(Type::Double(), isolate),
+      Name(Type::Name(), isolate),
+      UniqueName(Type::UniqueName(), isolate),
+      String(Type::String(), isolate),
+      InternalizedString(Type::InternalizedString(), isolate),
+      Symbol(Type::Symbol(), isolate),
+      Receiver(Type::Receiver(), isolate),
+      Object(Type::Object(), isolate),
+      Array(Type::Array(), isolate),
+      Function(Type::Function(), isolate),
+      Proxy(Type::Proxy(), isolate),
+      object_map(isolate->factory()->NewMap(JS_OBJECT_TYPE, 3 * kPointerSize)),
+      array_map(isolate->factory()->NewMap(JS_ARRAY_TYPE, 4 * kPointerSize)),
+      isolate_(isolate) {
+    object1 = isolate->factory()->NewJSObjectFromMap(object_map);
+    object2 = isolate->factory()->NewJSObjectFromMap(object_map);
+    array = isolate->factory()->NewJSArray(20);
+    ObjectClass = handle(Type::Class(object_map), isolate);
+    ArrayClass = handle(Type::Class(array_map), isolate);
+    ObjectConstant1 = handle(Type::Constant(object1), isolate);
+    ObjectConstant2 = handle(Type::Constant(object2), isolate);
+    ArrayConstant = handle(Type::Constant(array), isolate);
+  }
+
+  Handle<Type> None;
+  Handle<Type> Any;
+  Handle<Type> Oddball;
+  Handle<Type> Boolean;
+  Handle<Type> Null;
+  Handle<Type> Undefined;
+  Handle<Type> Number;
+  Handle<Type> Smi;
+  Handle<Type> Double;
+  Handle<Type> Name;
+  Handle<Type> UniqueName;
+  Handle<Type> String;
+  Handle<Type> InternalizedString;
+  Handle<Type> Symbol;
+  Handle<Type> Receiver;
+  Handle<Type> Object;
+  Handle<Type> Array;
+  Handle<Type> Function;
+  Handle<Type> Proxy;
+
+  Handle<Type> ObjectClass;
+  Handle<Type> ArrayClass;
+  Handle<Type> ObjectConstant1;
+  Handle<Type> ObjectConstant2;
+  Handle<Type> ArrayConstant;
+
+  Handle<Map> object_map;
+  Handle<Map> array_map;
+
+  Handle<JSObject> object1;
+  Handle<JSObject> object2;
+  Handle<JSArray> array;
+
+  Handle<Type> Union(Handle<Type> type1, Handle<Type> type2) {
+    return handle(Type::Union(type1, type2), isolate_);
+  }
+
+ private:
+  Isolate* isolate_;
+};
+
+
+TEST(Bitset) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  CHECK(IsBitset(*T.None));
+  CHECK(IsBitset(*T.Any));
+  CHECK(IsBitset(*T.String));
+  CHECK(IsBitset(*T.Object));
+
+  CHECK(IsBitset(Type::Union(T.String, T.Number)));
+  CHECK(IsBitset(Type::Union(T.String, T.Receiver)));
+  CHECK(IsBitset(Type::Optional(T.Object)));
+
+  CHECK_EQ(0, AsBitset(*T.None));
+  CHECK_EQ(AsBitset(*T.Number) | AsBitset(*T.String),
+           AsBitset(Type::Union(T.String, T.Number)));
+  CHECK_EQ(AsBitset(*T.Receiver),
+           AsBitset(Type::Union(T.Receiver, T.Object)));
+  CHECK_EQ(AsBitset(*T.String) | AsBitset(*T.Undefined),
+           AsBitset(Type::Optional(T.String)));
+}
+
+
+TEST(Class) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  CHECK(IsClass(*T.ObjectClass));
+  CHECK(IsClass(*T.ArrayClass));
+
+  CHECK(*T.object_map == AsClass(*T.ObjectClass));
+  CHECK(*T.array_map == AsClass(*T.ArrayClass));
+}
+
+
+TEST(Constant) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  CHECK(IsConstant(*T.ObjectConstant1));
+  CHECK(IsConstant(*T.ObjectConstant2));
+  CHECK(IsConstant(*T.ArrayConstant));
+
+  CHECK(*T.object1 == AsConstant(*T.ObjectConstant1));
+  CHECK(*T.object2 == AsConstant(*T.ObjectConstant2));
+  CHECK(*T.object1 != AsConstant(*T.ObjectConstant2));
+  CHECK(*T.array == AsConstant(*T.ArrayConstant));
+}
+
+
+static void CheckSub(Handle<Type> type1, Handle<Type> type2) {
+  CHECK(type1->Is(type2));
+  CHECK(!type2->Is(type1));
+  if (IsBitset(*type1) && IsBitset(*type2)) {
+    CHECK_NE(AsBitset(*type1), AsBitset(*type2));
+  }
+}
+
+static void CheckUnordered(Handle<Type> type1, Handle<Type> type2) {
+  CHECK(!type1->Is(type2));
+  CHECK(!type2->Is(type1));
+  if (IsBitset(*type1) && IsBitset(*type2)) {
+    CHECK_NE(AsBitset(*type1), AsBitset(*type2));
+  }
+}
+
+TEST(Is) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  // Reflexivity
+  CHECK(T.None->Is(T.None));
+  CHECK(T.Any->Is(T.Any));
+  CHECK(T.Object->Is(T.Object));
+
+  CHECK(T.ObjectClass->Is(T.ObjectClass));
+  CHECK(T.ObjectConstant1->Is(T.ObjectConstant1));
+
+  // Symmetry and Transitivity
+  CheckSub(T.None, T.Number);
+  CheckSub(T.None, T.Any);
+
+  CheckSub(T.Oddball, T.Any);
+  CheckSub(T.Boolean, T.Oddball);
+  CheckSub(T.Null, T.Oddball);
+  CheckSub(T.Undefined, T.Oddball);
+  CheckUnordered(T.Boolean, T.Null);
+  CheckUnordered(T.Undefined, T.Null);
+  CheckUnordered(T.Boolean, T.Undefined);
+
+  CheckSub(T.Number, T.Any);
+  CheckSub(T.Smi, T.Number);
+  CheckSub(T.Double, T.Number);
+  CheckUnordered(T.Smi, T.Double);
+
+  CheckSub(T.Name, T.Any);
+  CheckSub(T.UniqueName, T.Any);
+  CheckSub(T.UniqueName, T.Name);
+  CheckSub(T.String, T.Name);
+  CheckSub(T.InternalizedString, T.String);
+  CheckSub(T.InternalizedString, T.UniqueName);
+  CheckSub(T.InternalizedString, T.Name);
+  CheckSub(T.Symbol, T.UniqueName);
+  CheckSub(T.Symbol, T.Name);
+  CheckUnordered(T.String, T.UniqueName);
+  CheckUnordered(T.String, T.Symbol);
+  CheckUnordered(T.InternalizedString, T.Symbol);
+
+  CheckSub(T.Receiver, T.Any);
+  CheckSub(T.Object, T.Any);
+  CheckSub(T.Object, T.Receiver);
+  CheckSub(T.Array, T.Object);
+  CheckSub(T.Function, T.Object);
+  CheckSub(T.Proxy, T.Receiver);
+  CheckUnordered(T.Object, T.Proxy);
+  CheckUnordered(T.Array, T.Function);
+
+  // Structured subtyping
+  CheckSub(T.ObjectClass, T.Object);
+  CheckSub(T.ArrayClass, T.Object);
+  CheckUnordered(T.ObjectClass, T.ArrayClass);
+
+  CheckSub(T.ObjectConstant1, T.Object);
+  CheckSub(T.ObjectConstant2, T.Object);
+  CheckSub(T.ArrayConstant, T.Object);
+  CheckSub(T.ArrayConstant, T.Array);
+  CheckUnordered(T.ObjectConstant1, T.ObjectConstant2);
+  CheckUnordered(T.ObjectConstant1, T.ArrayConstant);
+
+  CheckUnordered(T.ObjectConstant1, T.ObjectClass);
+  CheckUnordered(T.ObjectConstant2, T.ObjectClass);
+  CheckUnordered(T.ObjectConstant1, T.ArrayClass);
+  CheckUnordered(T.ObjectConstant2, T.ArrayClass);
+  CheckUnordered(T.ArrayConstant, T.ObjectClass);
+}
+
+
+static void CheckOverlap(Handle<Type> type1, Handle<Type> type2) {
+  CHECK(type1->Maybe(type2));
+  CHECK(type2->Maybe(type1));
+  if (IsBitset(*type1) && IsBitset(*type2)) {
+    CHECK_NE(0, AsBitset(*type1) & AsBitset(*type2));
+  }
+}
+
+static void CheckDisjoint(Handle<Type> type1, Handle<Type> type2) {
+  CHECK(!type1->Is(type2));
+  CHECK(!type2->Is(type1));
+  CHECK(!type1->Maybe(type2));
+  CHECK(!type2->Maybe(type1));
+  if (IsBitset(*type1) && IsBitset(*type2)) {
+    CHECK_EQ(0, AsBitset(*type1) & AsBitset(*type2));
+  }
+}
+
+TEST(Maybe) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  CheckOverlap(T.Any, T.Any);
+  CheckOverlap(T.Object, T.Object);
+
+  CheckOverlap(T.Oddball, T.Any);
+  CheckOverlap(T.Boolean, T.Oddball);
+  CheckOverlap(T.Null, T.Oddball);
+  CheckOverlap(T.Undefined, T.Oddball);
+  CheckDisjoint(T.Boolean, T.Null);
+  CheckDisjoint(T.Undefined, T.Null);
+  CheckDisjoint(T.Boolean, T.Undefined);
+
+  CheckOverlap(T.Number, T.Any);
+  CheckOverlap(T.Smi, T.Number);
+  CheckOverlap(T.Double, T.Number);
+  CheckDisjoint(T.Smi, T.Double);
+
+  CheckOverlap(T.Name, T.Any);
+  CheckOverlap(T.UniqueName, T.Any);
+  CheckOverlap(T.UniqueName, T.Name);
+  CheckOverlap(T.String, T.Name);
+  CheckOverlap(T.InternalizedString, T.String);
+  CheckOverlap(T.InternalizedString, T.UniqueName);
+  CheckOverlap(T.InternalizedString, T.Name);
+  CheckOverlap(T.Symbol, T.UniqueName);
+  CheckOverlap(T.Symbol, T.Name);
+  CheckOverlap(T.String, T.UniqueName);
+  CheckDisjoint(T.String, T.Symbol);
+  CheckDisjoint(T.InternalizedString, T.Symbol);
+
+  CheckOverlap(T.Receiver, T.Any);
+  CheckOverlap(T.Object, T.Any);
+  CheckOverlap(T.Object, T.Receiver);
+  CheckOverlap(T.Array, T.Object);
+  CheckOverlap(T.Function, T.Object);
+  CheckOverlap(T.Proxy, T.Receiver);
+  CheckDisjoint(T.Object, T.Proxy);
+  CheckDisjoint(T.Array, T.Function);
+
+  CheckOverlap(T.ObjectClass, T.Object);
+  CheckOverlap(T.ArrayClass, T.Object);
+  CheckOverlap(T.ObjectClass, T.ObjectClass);
+  CheckOverlap(T.ArrayClass, T.ArrayClass);
+  CheckDisjoint(T.ObjectClass, T.ArrayClass);
+
+  CheckOverlap(T.ObjectConstant1, T.Object);
+  CheckOverlap(T.ObjectConstant2, T.Object);
+  CheckOverlap(T.ArrayConstant, T.Object);
+  CheckOverlap(T.ArrayConstant, T.Array);
+  CheckOverlap(T.ObjectConstant1, T.ObjectConstant1);
+  CheckDisjoint(T.ObjectConstant1, T.ObjectConstant2);
+  CheckDisjoint(T.ObjectConstant1, T.ArrayConstant);
+
+  CheckDisjoint(T.ObjectConstant1, T.ObjectClass);
+  CheckDisjoint(T.ObjectConstant2, T.ObjectClass);
+  CheckDisjoint(T.ObjectConstant1, T.ArrayClass);
+  CheckDisjoint(T.ObjectConstant2, T.ArrayClass);
+  CheckDisjoint(T.ArrayConstant, T.ObjectClass);
+}
+
+
+static void CheckEqual(Handle<Type> type1, Handle<Type> type2) {
+  CHECK_EQ(IsBitset(*type1), IsBitset(*type2));
+  CHECK_EQ(IsClass(*type1), IsClass(*type2));
+  CHECK_EQ(IsConstant(*type1), IsConstant(*type2));
+  CHECK_EQ(IsUnion(*type1), IsUnion(*type2));
+  if (IsBitset(*type1)) {
+    CHECK_EQ(AsBitset(*type1), AsBitset(*type2));
+  } else if (IsClass(*type1)) {
+    CHECK_EQ(AsClass(*type1), AsClass(*type2));
+  } else if (IsConstant(*type1)) {
+    CHECK_EQ(AsConstant(*type1), AsConstant(*type2));
+  } else if (IsUnion(*type1)) {
+    CHECK_EQ(AsUnion(*type1)->length(), AsUnion(*type2)->length());
+  }
+  CHECK(type1->Is(type2));
+  CHECK(type2->Is(type1));
+}
+
+TEST(Union) {
+  CcTest::InitializeVM();
+  Isolate* isolate = Isolate::Current();
+  HandleScope scope(isolate);
+  HandlifiedTypes T(isolate);
+
+  // Bitset-bitset
+  CHECK(IsBitset(Type::Union(T.Object, T.Number)));
+  CHECK(IsBitset(Type::Union(T.Object, T.Object)));
+  CHECK(IsBitset(Type::Union(T.Any, T.None)));
+
+  CheckEqual(T.Union(T.None, T.Number), T.Number);
+  CheckEqual(T.Union(T.Object, T.Proxy), T.Receiver);
+  CheckEqual(T.Union(T.Number, T.String), T.Union(T.String, T.Number));
+  CheckSub(T.Union(T.Number, T.String), T.Any);
+
+  // Class-class
+  CHECK(IsClass(Type::Union(T.ObjectClass, T.ObjectClass)));
+  CHECK(IsUnion(Type::Union(T.ObjectClass, T.ArrayClass)));
+
+  CheckEqual(T.Union(T.ObjectClass, T.ObjectClass), T.ObjectClass);
+  CheckSub(T.ObjectClass, T.Union(T.ObjectClass, T.ArrayClass));
+  CheckSub(T.ArrayClass, T.Union(T.ObjectClass, T.ArrayClass));
+  CheckSub(T.Union(T.ObjectClass, T.ArrayClass), T.Object);
+  CheckUnordered(T.Union(T.ObjectClass, T.ArrayClass), T.Array);
+  CheckOverlap(T.Union(T.ObjectClass, T.ArrayClass), T.Array);
+  CheckDisjoint(T.Union(T.ObjectClass, T.ArrayClass), T.Number);
+
+  // Constant-constant
+  CHECK(IsConstant(Type::Union(T.ObjectConstant1, T.ObjectConstant1)));
+  CHECK(IsUnion(Type::Union(T.ObjectConstant1, T.ObjectConstant2)));
+
+  CheckEqual(T.Union(T.ObjectConstant1, T.ObjectConstant1), T.ObjectConstant1);
+  CheckSub(T.ObjectConstant1, T.Union(T.ObjectConstant1, T.ObjectConstant2));
+  CheckSub(T.ObjectConstant2, T.Union(T.ObjectConstant1, T.ObjectConstant2));
+  CheckSub(T.Union(T.ObjectConstant1, T.ObjectConstant2), T.Object);
+  CheckUnordered(T.Union(T.ObjectConstant1, T.ObjectConstant2), T.ObjectClass);
+  CheckUnordered(T.Union(T.ObjectConstant1, T.ArrayConstant), T.Array);
+  CheckOverlap(T.Union(T.ObjectConstant1, T.ArrayConstant), T.Array);
+  CheckDisjoint(T.Union(T.ObjectConstant1, T.ArrayConstant), T.Number);
+  CheckDisjoint(T.Union(T.ObjectConstant1, T.ArrayConstant), T.ObjectClass);
+
+  // Bitset-class
+  CHECK(IsBitset(Type::Union(T.ObjectClass, T.Object)));
+  CHECK(IsUnion(Type::Union(T.ObjectClass, T.Number)));
+
+  CheckEqual(T.Union(T.ObjectClass, T.Object), T.Object);
+  CheckSub(T.Union(T.ObjectClass, T.Number), T.Any);
+  CheckSub(T.Union(T.ObjectClass, T.Smi), T.Union(T.Object, T.Number));
+  CheckSub(T.Union(T.ObjectClass, T.Array), T.Object);
+  CheckUnordered(T.Union(T.ObjectClass, T.String), T.Array);
+  CheckOverlap(T.Union(T.ObjectClass, T.String), T.Object);
+  CheckDisjoint(T.Union(T.ObjectClass, T.String), T.Number);
+
+  // Bitset-constant
+  CHECK(IsBitset(Type::Union(T.ObjectConstant1, T.Object)));
+  CHECK(IsUnion(Type::Union(T.ObjectConstant2, T.Number)));
+
+  CheckEqual(T.Union(T.ObjectConstant1, T.Object), T.Object);
+  CheckSub(T.Union(T.ObjectConstant1, T.Number), T.Any);
+  CheckSub(T.Union(T.ObjectConstant1, T.Smi), T.Union(T.Object, T.Number));
+  CheckSub(T.Union(T.ObjectConstant1, T.Array), T.Object);
+  CheckUnordered(T.Union(T.ObjectConstant1, T.String), T.Array);
+  CheckOverlap(T.Union(T.ObjectConstant1, T.String), T.Object);
+  CheckDisjoint(T.Union(T.ObjectConstant1, T.String), T.Number);
+
+  // Class-constant
+  CHECK(IsUnion(Type::Union(T.ObjectConstant1, T.ObjectClass)));
+  CHECK(IsUnion(Type::Union(T.ArrayClass, T.ObjectConstant2)));
+
+  CheckSub(T.Union(T.ObjectConstant1, T.ArrayClass), T.Object);
+  CheckSub(T.ObjectConstant1, T.Union(T.ObjectConstant1, T.ArrayClass));
+  CheckSub(T.ArrayClass, T.Union(T.ObjectConstant1, T.ArrayClass));
+  CheckUnordered(T.ObjectClass, T.Union(T.ObjectConstant1, T.ArrayClass));
+  CheckSub(
+      T.Union(T.ObjectConstant1, T.ArrayClass), T.Union(T.Array, T.Object));
+  CheckUnordered(T.Union(T.ObjectConstant1, T.ArrayClass), T.ArrayConstant);
+  CheckDisjoint(T.Union(T.ObjectConstant1, T.ArrayClass), T.ObjectConstant2);
+  CheckDisjoint(T.Union(T.ObjectConstant1, T.ArrayClass), T.ObjectClass);
+
+  // Bitset-union
+  CHECK(IsBitset(
+      Type::Union(T.Object, T.Union(T.ObjectConstant1, T.ObjectClass))));
+  CHECK(IsUnion(
+      Type::Union(T.Union(T.ArrayClass, T.ObjectConstant2), T.Number)));
+
+  CheckEqual(
+      T.Union(T.Object, T.Union(T.ObjectConstant1, T.ObjectClass)),
+      T.Object);
+  CheckEqual(
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant1), T.Number),
+      T.Union(T.ObjectConstant1, T.Union(T.Number, T.ArrayClass)));
+  CheckSub(
+      T.Double,
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant1), T.Number));
+  CheckSub(
+      T.ObjectConstant1,
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant1), T.Double));
+  CheckSub(
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant1), T.Double),
+      T.Any);
+  CheckSub(
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant1), T.Double),
+      T.Union(T.ObjectConstant1, T.Union(T.Number, T.ArrayClass)));
+
+  // Class-union
+  CHECK(IsUnion(
+      Type::Union(T.Union(T.ArrayClass, T.ObjectConstant2), T.ArrayClass)));
+  CHECK(IsUnion(
+      Type::Union(T.Union(T.ArrayClass, T.ObjectConstant2), T.ObjectClass)));
+
+  CheckEqual(
+      T.Union(T.ObjectClass, T.Union(T.ObjectConstant1, T.ObjectClass)),
+      T.Union(T.ObjectClass, T.ObjectConstant1));
+  CheckSub(
+      T.Union(T.ObjectClass, T.Union(T.ObjectConstant1, T.ObjectClass)),
+      T.Object);
+  CheckEqual(
+      T.Union(T.Union(T.ArrayClass, T.ObjectConstant2), T.ArrayClass),
+      T.Union(T.ArrayClass, T.ObjectConstant2));
+
+  // Constant-union
+  CHECK(IsUnion(Type::Union(
+      T.ObjectConstant1, T.Union(T.ObjectConstant1, T.ObjectConstant2))));
+  CHECK(IsUnion(Type::Union(
+      T.Union(T.ArrayConstant, T.ObjectClass), T.ObjectConstant1)));
+  CHECK(IsUnion(Type::Union(
+      T.Union(T.ArrayConstant, T.ObjectConstant2), T.ObjectConstant1)));
+
+  CheckEqual(
+      T.Union(T.ObjectConstant1, T.Union(T.ObjectConstant1, T.ObjectConstant2)),
+      T.Union(T.ObjectConstant2, T.ObjectConstant1));
+  CheckEqual(
+      T.Union(T.Union(T.ArrayConstant, T.ObjectConstant2), T.ObjectConstant1),
+      T.Union(T.ObjectConstant2, T.Union(T.ArrayConstant, T.ObjectConstant1)));
+
+  // Union-union
+  CHECK(IsBitset(
+      Type::Union(T.Union(T.Number, T.ArrayClass), T.Union(T.Smi, T.Array))));
+
+  CheckEqual(
+      T.Union(T.Union(T.ObjectConstant2, T.ObjectConstant1),
+              T.Union(T.ObjectConstant1, T.ObjectConstant2)),
+      T.Union(T.ObjectConstant2, T.ObjectConstant1));
+  CheckEqual(
+      T.Union(T.Union(T.ObjectConstant2, T.ArrayConstant),
+              T.Union(T.ObjectConstant1, T.ArrayConstant)),
+      T.Union(T.Union(T.ObjectConstant1, T.ObjectConstant2), T.ArrayConstant));
+  CheckEqual(
+      T.Union(T.Union(T.Number, T.ArrayClass), T.Union(T.Smi, T.Array)),
+      T.Union(T.Number, T.Array));
+}