Split World usage into open, inference, and closed world.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index c7d00d86ee179ed61a4f472d2254a4c2290556e5..4b90f49a60df6b4ac33d555860c3a7adba6fd07d 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -77,7 +77,7 @@ import 'universe/universe.dart' show Universe;
 import 'universe/use.dart' show StaticUse;
 import 'universe/world_impact.dart' show ImpactStrategy, WorldImpact;
 import 'util/util.dart' show Link, Setlet;
-import 'world.dart' show World;
+import 'world.dart' show ClosedWorld, ClosedWorldRefiner, World;
 
 typedef Backend MakeBackendFuncion(Compiler compiler);
 
@@ -88,7 +88,7 @@ abstract class Compiler implements LibraryLoaderListener {
   Measurer get measurer;
 
   final IdGenerator idGenerator = new IdGenerator();
-  World world;
+  World _world;
   Types types;
   _CompilerCoreTypes _coreTypes;
   CompilerDiagnosticReporter _reporter;
@@ -225,7 +225,7 @@ abstract class Compiler implements LibraryLoaderListener {
         this.userOutputProvider = outputProvider == null
             ? const NullCompilerOutput()
             : outputProvider {
-    world = new World(this);
+    _world = new World(this);
     if (makeReporter != null) {
       _reporter = makeReporter(this, options);
     } else {
@@ -302,6 +302,16 @@ abstract class Compiler implements LibraryLoaderListener {
     tasks.addAll(backend.tasks);
   }
 
+  /// The world currently being computed by resolution. This forms a basis for
+  /// the [inferenceWorld] and later the [closedWorld].
+  World get openWorld => _world;
+
+  /// The closed world after resolution but currently refined by inference.
+  ClosedWorldRefiner get inferenceWorld => _world;
+
+  /// The closed world after resolution and inference.
+  ClosedWorld get closedWorld => _world;
+
   /// Creates the scanner task.
   ///
   /// Override this to mock the scanner for testing.
@@ -314,7 +324,7 @@ abstract class Compiler implements LibraryLoaderListener {
   /// Override this to mock the resolver for testing.
   ResolverTask createResolverTask() {
     return new ResolverTask(
-        resolution, backend.constantCompilerTask, world, measurer);
+        resolution, backend.constantCompilerTask, openWorld, measurer);
   }
 
   Universe get resolverWorld => enqueuer.resolution.universe;
@@ -709,7 +719,7 @@ abstract class Compiler implements LibraryLoaderListener {
         assert(mainFunction != null);
         phase = PHASE_DONE_RESOLVING;
 
-        world.populate();
+        openWorld.populate();
         // Compute whole-program-knowledge that the backend needs. (This might
         // require the information computed in [world.populate].)
         backend.onResolutionComplete();
@@ -1982,7 +1992,7 @@ class _CompilerResolution implements Resolution {
 
   @override
   void registerClass(ClassElement cls) {
-    compiler.world.registerClass(cls);
+    compiler.openWorld.registerClass(cls);
   }
 
   @override