Allow patch files to add top-level declarations to the patched library.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index 6b130e442bb074e78040abd5a662f3bb11e6d8d2..1f060b13f65c78825f04b1c2c2b8ab4ec6acb344 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -534,7 +534,7 @@ class Compiler implements DiagnosticListener {
         Uri resolved = patchBase.resolve(argument.dartString.slowToString());
         LibraryElement importedLibrary =
             scanner.loadLibrary(resolved, argument);
-        scanner.importLibrary(original, importedLibrary, tag, patch);
+        scanner.importLibrary(original, importedLibrary, tag, patch.script);
         if (resolved.scheme == "dart") {
           delayedPatches[resolved.path] = importedLibrary;
         }
@@ -588,11 +588,20 @@ class Compiler implements DiagnosticListener {
           }
         }
       } else if (originalElement === null) {
+        // The original library does not have an element with the same name
+        // as the patch library element.
+        // In this case, the patch library element must not be marked as
+        // "patch", and its name must make it private.
         if (isPatchElement(patchElement)) {
           internalError("Cannot patch non-existing member '"
                         "${patchElement.name.slowToString()}'.");
         }
-        original.addMember(clonePatch(patchElement), this);
+        if (!patchElement.name.isPrivate()) {
+          internalError("Cannot add non-private member '"
+                        "${patchElement.name.slowToString()}' from patch.");
+        }
+        Element cloneElement = patchElement.cloneTo(original, this);
+        original.addMember(cloneElement, this);
       } else {
         patchMember(originalElement, patchElement);
       }
@@ -606,20 +615,6 @@ class Compiler implements DiagnosticListener {
     return !element.metadata.isEmpty();
   }
 
-  Element clonePatch(Element patchElement) {
-    // The original library does not have an element with the same name
-    // as the patch library element.
-    // In this case, the patch library element must not be marked as "patch",
-    // and its name must make it private.
-    if (!patchElement.name.isPrivate()) {
-      internalError("Cannot add non-private member '"
-                    "${patchElement.name.slowToString()}' from patch.");
-    }
-    // TODO(lrn): Create a copy of patchElement that isn't added to any
-    // object/library yet, but which takes its source from patchElement.
-    throw "Adding members from patch is unsupported";
-  }
-
   void patchMember(Element originalElement, Element patchElement) {
     // The original library has an element with the same name as the patch
     // library element.
@@ -978,7 +973,7 @@ class Compiler implements DiagnosticListener {
       throw 'Cannot find tokens to produce error message.';
     }
     if (uri === null && currentElement !== null) {
-      uri = currentElement.getCompilationUnit().script.uri;
+      uri = currentElement.getScript().uri;
     }
     return SourceSpan.withCharacterOffsets(begin, end,
       (beginOffset, endOffset) => new SourceSpan(uri, beginOffset, endOffset));
@@ -1002,7 +997,7 @@ class Compiler implements DiagnosticListener {
       element = currentElement;
     }
     Token position = element.position();
-    Uri uri = element.getCompilationUnit().script.uri;
+    Uri uri = element.getScript().uri;
     return (position === null)
         ? new SourceSpan(uri, 0, 0)
         : spanFromTokens(position, position, uri);