Get more data to track down issue 25884

pkg/analysis_server/lib/src/computer/computer_overrides.dart

Index: pkg/analysis_server/lib/src/computer/computer_overrides.dart
diff --git a/pkg/analysis_server/lib/src/computer/computer_overrides.dart b/pkg/analysis_server/lib/src/computer/computer_overrides.dart
index 4eb93d1bf22a0d97fcfbd1c2a0576a02f9c2dbae..f4d47f8e104cb9db358e2a73bd18d3570352dccc 100644
--- a/pkg/analysis_server/lib/src/computer/computer_overrides.dart
+++ b/pkg/analysis_server/lib/src/computer/computer_overrides.dart
@@ -138,6 +138,14 @@ class _OverriddenElementsFinder {
   _OverriddenElementsFinder(Element seed) {
     _seed = seed;
     _class = seed.enclosingElement;
+    if (_class == null) {
+      // TODO(brianwilkerson) Remove this code when the issue has been fixed
+      // (https://github.com/dart-lang/sdk/issues/25884)
+      Type type = seed.runtimeType;
+      String name = seed.name;
+      throw new ArgumentError(
+          'The $type named $name does not have an enclosing element');
+    }
     _library = _class.library;
     _name = seed.displayName;
     if (seed is MethodElement) {