Resynthesize invalid types as 'dynamic'.

pkg/analyzer/lib/src/summary/resynthesize.dart

Index: pkg/analyzer/lib/src/summary/resynthesize.dart
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index 8fe29d906d01ebbf00f835c3dbc785e46c854c32..12a8c015b0befab11292f3d1cf003e3b4d0438d0 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -1248,9 +1248,7 @@ class _ReferenceInfo {
             : _buildType(instantiateToBoundsAllowed, numTypeArguments,
                 getTypeArgument, implicitFunctionTypeIndices);
     if (result == null) {
-      // TODO(paulberry): figure out how to handle this case (which should
-      // only occur in the event of erroneous code).
-      throw new UnimplementedError();
+      return DynamicTypeImpl.instance;
     }
     return result;
   }