anchor.diff:      var declaredTypeParameters = _declaredMethod.function.typeParameters;
       for (int i = _start; i < _end; i++) {
         var candidate = _candidates[i];
  +      if (candidate is SyntheticAccessor) {
  +        // This can happen if there are errors.  Just skip this override.
  +        continue;
  +      }
         var candidateFunction = candidate.function;
         if (candidateFunction == null) {
           // This can happen if there are errors.  Just skip this override.
  
positive.code: 
    SyntheticAccessor(
        Name name, ProcedureKind kind, FunctionNode function, this._field)
        : super(name, kind, function);
  
    @override
    int get fileOffset => _field.fileOffset;
  
    @override
    String get fileUri => _field.fileUri;
  
    static getField(SyntheticAccessor accessor) => accessor._field;
  }
  
negative.code:       for (var fix in covarianceFixes) {
          fix(function);
        }
        return inheritedMember;
      }
    }
  