anchor.diff:      _annotationProcessor = KernelAnnotationProcessor(
           elementMap, elementMap.nativeBasicDataBuilder, _irAnnotationData);
       for (Uri uri in libraries) {
  -      LibraryEntity library = elementEnvironment.lookupLibrary(uri);
  +      LibraryEntity library = elementEnvironment.lookupLibrary(uri)!;
         if (maybeEnableNative(library.canonicalUri)) {
           _annotationProcessor.extractNativeAnnotations(library);
         }
  
positive.code: // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  // @dart = 2.10
  
  library dart2js.kernel.frontend_strategy;
  
  
negative.code:             _rtiNeedBuilder,
              _annotationsData,
              impactBuilderData);
          _impactCache[element] = worldImpact;
          return worldImpact;
        });
      });
  