@Override
      public void visitLambdaExpression(@NotNull PsiLambdaExpression lambda) {
        super.visitLambdaExpression(lambda);
        PsiElement body = lambda.getBody();
        if (body instanceof PsiExpression) {
          checkCollectionNullityOnAssignment(body, LambdaUtil.getFunctionalInterfaceReturnType(lambda), (PsiExpression)body);
        }
      }
@Override
      public void visitLambdaExpression(@NotNull PsiLambdaExpression lambda)