Constrain type annotations with deferred types.

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 7fdb7966ec1664601098592166786b1d23c9bd8a..7543c7a37a25c8868055cb235f2159a40f355409 100644
--- a/sdk/lib/_internal/compiler/implementation/deferred_load.dart
+++ b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
@@ -13,6 +13,9 @@ import 'dart2jslib.dart' show
     StringConstant,
     invariant;
 
+import 'dart_backend/dart_backend.dart' show
+    DartBackend;
+
 import 'elements/elements.dart' show
     Element,
     ClassElement,
@@ -22,6 +25,7 @@ import 'elements/elements.dart' show
     LibraryElement,
     MetadataAnnotation,
     ScopeContainerElement,
+    PrefixElement,
     ClosureContainer;
 
 import 'util/util.dart' show
@@ -186,17 +190,31 @@ class DeferredLoadTask extends CompilerTask {
 
   /// Answers whether the [import] has a [DeferredLibrary] annotation.
   bool _isImportDeferred(Import import) {
-    Link<MetadataAnnotation> metadatalist = import.metadata;
-    if (metadatalist == null) return false;
-    for (MetadataAnnotation metadata in metadatalist) {
+    return _allDeferredImports.containsKey(import);
+  }
+
+  /// Checks whether the [import] has a [DeferredLibrary] annotation and stores
+  /// the information in [_allDeferredImports] and on the corresponding
+  /// prefixElement.
+  void _markIfDeferred(Import import, LibraryElement library) {
+    Link<MetadataAnnotation> metadataList = import.metadata;
+    if (metadataList == null) return;
+    for (MetadataAnnotation metadata in metadataList) {
       metadata.ensureResolved(compiler);
       Element element = metadata.value.computeType(compiler).element;
-      if (metadata.value.computeType(compiler).element
-          == deferredLibraryClass) {
-        return true;
+      if (element == deferredLibraryClass) {
+        _allDeferredImports[import] = library.getLibraryFromTag(import);
+        // On encountering a deferred library without a prefix we report an
+        // error, but continue the compilation to possibly give more
+        // information. Therefore it is neccessary to check if there is a prefix
+        // here.
+        Element maybePrefix = library.find(import.prefix.toString());
+        if (maybePrefix != null && maybePrefix.isPrefix()) {
+          PrefixElement prefix = maybePrefix;
+          prefix.markAsDeferred();
+        }
       }
     }
-    return false;
   }
 
   /// Answers whether [element] is explicitly deferred when referred to from
@@ -652,7 +670,7 @@ class DeferredLoadTask extends CompilerTask {
     // import "lib.dart" as a;
     // import "lib2.dart" as a;
     // We must be able to signal error for case 1, 2, 3, but accept case 4.
-    
+
     // The prefixes that have been used by any imports in this library.
     Setlet<String> usedPrefixes = new Setlet<String>();
     // The last deferred import we saw with a given prefix (if any).
@@ -666,6 +684,7 @@ class DeferredLoadTask extends CompilerTask {
         for (LibraryTag tag in library.tags) {
           if (tag is! Import) continue;
           Import import = tag;
+          _markIfDeferred(import, library);
           String prefix = (import.prefix != null)
               ? import.prefix.toString()
               : null;
@@ -680,7 +699,6 @@ class DeferredLoadTask extends CompilerTask {
               prefixDeferredImport[prefix] = import;
             }
             splitProgram = true;
-            _allDeferredImports[tag] = library.getLibraryFromTag(tag);
             lastDeferred = import.metadata.first;
             if (library == compiler.mainApp) {
               deferredUsedFromMain = true;
@@ -700,6 +718,13 @@ class DeferredLoadTask extends CompilerTask {
         }
       });
     }
+    if (splitProgram && compiler.backend is DartBackend) {
+      // TODO(sigurdm): Implement deferred loading for dart2dart.
+      splitProgram = false;
+      compiler.reportInfo(
+          lastDeferred,
+          MessageKind.DEFERRED_LIBRARY_DART_2_DART);
+    }
     if (splitProgram && !deferredUsedFromMain) {
       compiler.reportInfo(
           lastDeferred,