Insert checks before deferred calls and accesses.

sdk/lib/_internal/compiler/implementation/deferred_load.dart

Index: sdk/lib/_internal/compiler/implementation/deferred_load.dart
diff --git a/sdk/lib/_internal/compiler/implementation/deferred_load.dart b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
index 81fba7f2e24ee2b806c4a7e567914439852eaeaa..01552e10b998c135a0ac342ea3ad3b7a535950b1 100644
--- a/sdk/lib/_internal/compiler/implementation/deferred_load.dart
+++ b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
@@ -12,11 +12,15 @@ import 'dart2jslib.dart' show
     ConstructedConstant,
     MessageKind,
     StringConstant,
-    invariant;
+    invariant,
+    Backend;
 
 import 'dart_backend/dart_backend.dart' show
     DartBackend;
 
+import 'js_backend/js_backend.dart' show
+    JavaScriptBackend;
+
 import 'elements/elements.dart' show
     Element,
     ClassElement,
@@ -43,6 +47,8 @@ import 'tree/tree.dart' show
     LiteralString,
     LiteralDartString;
 
+import 'tree/tree.dart' as ast;
+
 import 'resolution/resolution.dart' show
     TreeElements;
 
@@ -180,6 +186,11 @@ class DeferredLoadTask extends CompilerTask {
     return outputUnitForElement(element) != mainOutputUnit;
   }
 
+  /// Returns true if e1 and e2 are in the same output unit.
+  bool inSameOutputUnit(Element e1, Element e2) {
+    return outputUnitForElement(e1) == outputUnitForElement(e2);
+  }
+
   /// Mark that [import] is part of the [OutputputUnit] for [element].
   ///
   /// [element] can be either a [Constant] or an [Element].
@@ -257,10 +268,12 @@ class DeferredLoadTask extends CompilerTask {
 
   /// Returns a [Link] of every [Import] that imports [element] into [library].
   Link<Import> _getImports(Element element, LibraryElement library) {
-    if (!element.isTopLevel()) {
+    if (element.isMember()) {
       element = element.getEnclosingClass();
     }
-
+    if (element.isAccessor()) {
+      element = (element as FunctionElement).abstractField;
+    }
     return library.getImportsFor(element);
   }
 
@@ -802,6 +815,10 @@ class DeferredLoadTask extends CompilerTask {
         }
       });
     }
+    Backend backend = compiler.backend;
+    if (splitProgram && backend is JavaScriptBackend) {
+      backend.registerCheckDeferredIsLoaded(compiler.globalDependencies);
+    }
     if (splitProgram && backend is DartBackend) {
       // TODO(sigurdm): Implement deferred loading for dart2dart.
       splitProgram = false;
@@ -810,4 +827,60 @@ class DeferredLoadTask extends CompilerTask {
           MessageKind.DEFERRED_LIBRARY_DART_2_DART);
     }
   }
+
+  /// If [send] is a static send with a deferred element, returns the
+  /// [PrefixElement] that the first prefix of the send resolves to.
+  /// Otherwise returns null.
+  ///
+  /// Precondition: send must be static.
+  ///
+  /// Example:
+  ///
+  /// import "a.dart" deferred as a;
+  ///
+  /// main() {
+  ///   print(a.loadLibrary.toString());
+  ///   a.loadLibrary().then((_) {
+  ///     a.run();
+  ///     a.foo.method();
+  ///   });
+  /// }
+  ///
+  /// Returns null for a.loadLibrary() (the special
+  /// function loadLibrary is not deferred). And returns the PrefixElement for
+  /// a.run() and a.foo.
+  /// a.loadLibrary.toString() and a.foo.method() are dynamic sends - and
+  /// this functions should not be called on them.
+  PrefixElement deferredPrefixElement(ast.Send send, TreeElements elements) {
+    Element element = elements[send];
+    // The DeferredLoaderGetter is not deferred, therefore we do not return the
+    // prefix.
+    if (element != null && element.isDeferredLoaderGetter()) return null;
+
+    ast.Node firstNode(ast.Node node) {
+      if (node is! ast.Send) {
+        return node;
+      } else {
+        ast.Send send = node;
+        ast.Node receiver = send.receiver;
+        ast.Node receiverFirst = firstNode(receiver);
+        if (receiverFirst != null) {
+          return receiverFirst;
+        } else {
+          return firstNode(send.selector);
+        }
+      }
+    }
+    ast.Node first = firstNode(send);
+    ast.Node identifier = first.asIdentifier();
+    if (identifier == null) return null;
+    Element maybePrefix = elements[identifier];
+    if (maybePrefix != null && maybePrefix.isPrefix()) {
+      PrefixElement prefixElement = maybePrefix;
+      if (prefixElement.isDeferred) {
+        return prefixElement;
+      }
+    }
+    return null;
+  }
 }