Normalize type masks to use the least upper instantiated subclass/type.

tests/compiler/dart2js/type_mask2_test.dart

Index: tests/compiler/dart2js/type_mask2_test.dart
diff --git a/tests/compiler/dart2js/type_mask2_test.dart b/tests/compiler/dart2js/type_mask2_test.dart
index 25c19e10ce813fc2729c2dcfb0ed2c96a8eab0e2..03db5802e1599e2bf63fb558f39237b427076cf7 100644
--- a/tests/compiler/dart2js/type_mask2_test.dart
+++ b/tests/compiler/dart2js/type_mask2_test.dart
@@ -4,12 +4,15 @@
 
 library type_mask2_test;
 
+import 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'type_test_helper.dart';
 import 'package:compiler/src/elements/elements.dart'
        show Element, ClassElement;
 import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/world.dart' show
+    ClassWorld;
 
 isCheckedMode() {
   try {
@@ -22,11 +25,67 @@ isCheckedMode() {
 }
 
 void main() {
-  testUnionTypeMaskFlatten();
+  asyncTest(() async {
+    await testUnionTypeMaskFlatten();
+    await testStringSubtypes();
+  });
 }
 
-void testUnionTypeMaskFlatten() {
-  asyncTest(() => TypeEnvironment.create(r"""
+checkMasks(ClassWorld classWorld,
+           List<ClassElement> allClasses,
+           List<FlatTypeMask> masks,
+           {FlatTypeMask result,
+            List<FlatTypeMask> disjointMasks,
+            FlatTypeMask flattened,
+            List<ClassElement> containedClasses}) {
+  List<FlatTypeMask> disjoint = <FlatTypeMask>[];
+  UnionTypeMask.unionOfHelper(masks, disjoint, classWorld);
+  Expect.listEquals(disjointMasks, disjoint,
+      'Unexpected disjoint masks: $disjoint, expected $disjointMasks.');
+  if (flattened == null) {
+    // We only do the invalid call to flatten in checked mode, as flatten's
+    // behaviour in unchecked mode is not defined and thus cannot be
+    // reliably tested.
+    if (isCheckedMode()) {
+      Expect.throws(() => UnionTypeMask.flatten(disjoint, classWorld),
+        (e) => e is AssertionError,
+        'Expect assertion failure on flattening of $disjoint.');
+    }
+  } else {
+    TypeMask flattenResult =
+        UnionTypeMask.flatten(disjoint, classWorld);
+    Expect.equals(flattened, flattenResult,
+        'Unexpected flattening of $disjoint: '
+        '$flattenResult, expected $flattened.');
+  }
+  var union = UnionTypeMask.unionOf(masks, classWorld);
+  if (result == null) {
+    Expect.isTrue(union is UnionTypeMask,
+        'Expected union of $masks to be a union-type: $union.');
+    Expect.listEquals(disjointMasks, union.disjointMasks,
+        'Unexpected union masks: '
+        '${union.disjointMasks}, expected $disjointMasks.');
+  } else {
+    Expect.equals(result, union,
+        'Unexpected union of $masks: $union, expected $result.');
+  }
+  if (containedClasses != null) {
+    for (ClassElement cls in allClasses) {
+      if (containedClasses.contains(cls)) {
+        Expect.isTrue(union.contains(cls, classWorld),
+            'Expected $union to contain $cls.');
+      } else {
+        Expect.isFalse(union.contains(cls, classWorld),
+            '$union not expected to contain $cls.');
+      }
+    }
+
+  }
+  return union;
+}
+
+Future testUnionTypeMaskFlatten() async  {
+  TypeEnvironment env = await TypeEnvironment.create(r"""
       class A {}
       class B {}
       class C extends A {}
@@ -42,153 +101,158 @@ void testUnionTypeMaskFlatten() {
         new E();
       }
       """,
-      useMockCompiler: false).then((env) {
+      useMockCompiler: false);
+
+  ClassWorld classWorld = env.compiler.world;
+
+  ClassElement Object_ = env.getElement("Object");
+  ClassElement A = env.getElement("A");
+  ClassElement B = env.getElement("B");
+  ClassElement C = env.getElement("C");
+  ClassElement D = env.getElement("D");
+  ClassElement E = env.getElement("E");
+
+  List<ClassElement> allClasses = <ClassElement>[Object_, A, B, C, D, E];
+
+  check(List<FlatTypeMask> masks,
+        {FlatTypeMask result,
+         List<FlatTypeMask> disjointMasks,
+         FlatTypeMask flattened,
+         List<ClassElement> containedClasses}) {
+    return checkMasks(
+        classWorld,
+        allClasses,
+        masks,
+        result: result,
+        disjointMasks: disjointMasks,
+        flattened: flattened,
+        containedClasses: containedClasses);
+  }
+
+  TypeMask empty = const TypeMask.nonNullEmpty();
+  TypeMask subclassObject = new TypeMask.nonNullSubclass(Object_, classWorld);
+  TypeMask exactA = new TypeMask.nonNullExact(A, classWorld);
+  TypeMask subclassA = new TypeMask.nonNullSubclass(A, classWorld);
+  TypeMask subtypeA = new TypeMask.nonNullSubtype(A, classWorld);
+  TypeMask exactB = new TypeMask.nonNullExact(B, classWorld);
+  TypeMask subclassB = new TypeMask.nonNullSubclass(B, classWorld);
+  TypeMask exactC = new TypeMask.nonNullExact(C, classWorld);
+  TypeMask exactD = new TypeMask.nonNullExact(D, classWorld);
+  TypeMask exactE = new TypeMask.nonNullExact(E, classWorld);
+
+  check([],
+        result: empty,
+        disjointMasks: [],
+        containedClasses: []);
+
+  check([exactA],
+        result: exactA,
+        disjointMasks: [exactA],
+        containedClasses: [A]);
+
+  check([exactA, exactA],
+        result: exactA,
+        disjointMasks: [exactA],
+        containedClasses: [A]);
+
+  check([exactA, exactB],
+        disjointMasks: [exactA, exactB],
+        flattened: subclassObject,
+        containedClasses: [A, B]);
+
+  check([subclassObject],
+        result: subclassObject,
+        disjointMasks: [subclassObject],
+        containedClasses: [Object_, A, B, C, D, E]);
+
+  check([subclassObject, exactA],
+        disjointMasks: [subclassObject],
+        result: subclassObject,
+        containedClasses: [Object_, A, B, C, D, E]);
+
+  check([exactA, exactC],
+        disjointMasks: [subclassA],
+        result: subclassA,
+        containedClasses: [A, C]);
+
+  check([exactA, exactB, exactC],
+        disjointMasks: [subclassA, exactB],
+        flattened: subclassObject,
+        containedClasses: [A, B, C]);
+
+  check([exactA, exactD],
+        disjointMasks: [subtypeA],
+        result: subtypeA,
+        containedClasses: [A, C, D, E]);
+
+  check([exactA, exactB, exactD],
+        disjointMasks: [subtypeA, exactB],
+        flattened: subclassObject,
+        containedClasses: [A, B, C, D, E]);
+
+  check([exactA, exactE],
+        disjointMasks: [subtypeA],
+        result: subtypeA,
+        containedClasses: [A, C, D, E]);
+
+  check([exactA, exactB, exactE],
+        disjointMasks: [subtypeA, exactB],
+        flattened: subclassObject,
+        containedClasses: [A, B, C, D, E]);
+
+  check([exactB, exactE, exactA],
+        disjointMasks: [subclassB, exactA],
+        flattened: subclassObject,
+        containedClasses: [A, B, E]);
+
+  check([exactE, exactA, exactB],
+        disjointMasks: [subtypeA, exactB],
+        flattened: subclassObject,
+        containedClasses: [A, B, C, D, E]);
+
+  check([exactE, exactB, exactA],
+        disjointMasks: [subclassB, exactA],
+        flattened: subclassObject,
+        containedClasses: [A, B, E]);
+}
+
+Future testStringSubtypes() async {
+  TypeEnvironment env = await TypeEnvironment.create('',
+      mainSource: r"""
+      main() {
+        '' is String;
+      }
+      """,
+      useMockCompiler: false);
     var classWorld = env.compiler.world;
+    var backend = env.compiler.backend;
 
     ClassElement Object_ = env.getElement("Object");
-    ClassElement A = env.getElement("A");
-    ClassElement B = env.getElement("B");
-    ClassElement C = env.getElement("C");
-    ClassElement D = env.getElement("D");
-    ClassElement E = env.getElement("E");
-
-    List<ClassElement> allClasses = <ClassElement>[Object_, A, B, C, D, E];
-
-    check(List<FlatTypeMask> masks,
-          {FlatTypeMask result,
-           List<FlatTypeMask> disjointMasks,
-           FlatTypeMask flattened,
-           List<ClassElement> containedClasses}) {
-      List<FlatTypeMask> disjoint = <FlatTypeMask>[];
-      UnionTypeMask.unionOfHelper(masks, disjoint, classWorld);
-      Expect.listEquals(disjointMasks, disjoint,
-          'Unexpected disjoint masks: $disjoint, expected $disjointMasks.');
-      if (flattened == null) {
-        // We only do the invalid call to flatten in checked mode, as flatten's
-        // brehaviour in unchecked more is not defined and thus cannot be
-        // reliably tested.
-        if (isCheckedMode()) {
-          Expect.throws(() => UnionTypeMask.flatten(disjoint, classWorld),
-            (e) => e is AssertionError,
-            'Expect assertion failure on flattening of $disjoint.');
-        }
-      } else {
-        TypeMask flattenResult =
-            UnionTypeMask.flatten(disjoint, classWorld);
-        Expect.equals(flattened, flattenResult,
-            'Unexpected flattening of $disjoint: '
-            '$flattenResult, expected $flattened.');
-      }
-      var union = UnionTypeMask.unionOf(masks, classWorld);
-      if (result == null) {
-        Expect.isTrue(union is UnionTypeMask,
-            'Expected union of $masks to be a union-type: $union.');
-        Expect.listEquals(disjointMasks, union.disjointMasks,
-            'Unexpected union masks: '
-            '${union.disjointMasks}, expected $disjointMasks.');
-      } else {
-        Expect.equals(result, union,
-            'Unexpected union of $masks: $union, expected $result.');
-      }
-      if (containedClasses != null) {
-        for (ClassElement cls in allClasses) {
-          if (containedClasses.contains(cls)) {
-            Expect.isTrue(union.contains(cls, classWorld),
-                'Expected $union to contain $cls.');
-          } else {
-            Expect.isFalse(union.contains(cls, classWorld),
-                '$union not expected to contain $cls.');
-          }
-        }
+    ClassElement String_ = env.getElement("String");
+    ClassElement JSString = backend.helpers.jsStringClass;
 
-      }
-      return union;
-    }
+    List<ClassElement> allClasses = <ClassElement>[Object_, String_];
+
+    Expect.isFalse(classWorld.isDirectlyInstantiated(Object_));
+    Expect.isTrue(classWorld.isIndirectlyInstantiated(Object_));
+    Expect.isTrue(classWorld.isInstantiated(Object_));
+
+    Expect.isFalse(classWorld.isDirectlyInstantiated(String_));
+    Expect.isFalse(classWorld.isIndirectlyInstantiated(String_));
+    Expect.isFalse(classWorld.isInstantiated(String_));
+
+    Expect.isTrue(classWorld.isDirectlyInstantiated(JSString));
+    Expect.isFalse(classWorld.isIndirectlyInstantiated(JSString));
+    Expect.isTrue(classWorld.isInstantiated(JSString));
+
+    TypeMask subtypeString = new TypeMask.nonNullSubtype(String_, classWorld);
+    TypeMask exactJSString = new TypeMask.nonNullExact(JSString, classWorld);
+    TypeMask subtypeJSString =
+        new TypeMask.nonNullSubtype(JSString, classWorld);
+    TypeMask subclassJSString =
+        new TypeMask.nonNullSubclass(JSString, classWorld);
 
-    TypeMask empty = const TypeMask.nonNullEmpty();
-    TypeMask subclassObject = new TypeMask.nonNullSubclass(Object_, classWorld);
-    TypeMask exactA = new TypeMask.nonNullExact(A, classWorld);
-    TypeMask subclassA = new TypeMask.nonNullSubclass(A, classWorld);
-    TypeMask subtypeA = new TypeMask.nonNullSubtype(A, classWorld);
-    TypeMask exactB = new TypeMask.nonNullExact(B, classWorld);
-    TypeMask subclassB = new TypeMask.nonNullSubclass(B, classWorld);
-    TypeMask exactC = new TypeMask.nonNullExact(C, classWorld);
-    TypeMask exactD = new TypeMask.nonNullExact(D, classWorld);
-    TypeMask exactE = new TypeMask.nonNullExact(E, classWorld);
-
-    check([],
-          result: empty,
-          disjointMasks: [],
-          containedClasses: []);
-
-    check([exactA],
-          result: exactA,
-          disjointMasks: [exactA],
-          containedClasses: [A]);
-
-    check([exactA, exactA],
-          result: exactA,
-          disjointMasks: [exactA],
-          containedClasses: [A]);
-
-    check([exactA, exactB],
-          disjointMasks: [exactA, exactB],
-          flattened: subclassObject,
-          containedClasses: [A, B]);
-
-    check([subclassObject],
-          result: subclassObject,
-          disjointMasks: [subclassObject],
-          containedClasses: [Object_, A, B, C, D, E]);
-
-    check([subclassObject, exactA],
-          disjointMasks: [subclassObject],
-          result: subclassObject,
-          containedClasses: [Object_, A, B, C, D, E]);
-
-    check([exactA, exactC],
-          disjointMasks: [subclassA],
-          result: subclassA,
-          containedClasses: [A, C]);
-
-    check([exactA, exactB, exactC],
-          disjointMasks: [subclassA, exactB],
-          flattened: subclassObject,
-          containedClasses: [A, B, C]);
-
-    check([exactA, exactD],
-          disjointMasks: [subtypeA],
-          result: subtypeA,
-          containedClasses: [A, C, D, E]);
-
-    check([exactA, exactB, exactD],
-          disjointMasks: [subtypeA, exactB],
-          flattened: subclassObject,
-          containedClasses: [A, B, C, D, E]);
-
-    check([exactA, exactE],
-          disjointMasks: [subtypeA],
-          result: subtypeA,
-          containedClasses: [A, C, D, E]);
-
-    check([exactA, exactB, exactE],
-          disjointMasks: [subtypeA, exactB],
-          flattened: subclassObject,
-          containedClasses: [A, B, C, D, E]);
-
-    check([exactB, exactE, exactA],
-          disjointMasks: [subclassB, exactA],
-          flattened: subclassObject,
-          containedClasses: [A, B, E]);
-
-    check([exactE, exactA, exactB],
-          disjointMasks: [subtypeA, exactB],
-          flattened: subclassObject,
-          containedClasses: [A, B, C, D, E]);
-
-    check([exactE, exactB, exactA],
-          disjointMasks: [subclassB, exactA],
-          flattened: subclassObject,
-          containedClasses: [A, B, E]);
-  }));
+    Expect.equals(exactJSString, subtypeString);
+    Expect.equals(exactJSString, subtypeJSString);
+    Expect.equals(exactJSString, subclassJSString);
 }