[BUG]: Compiler fails to generate default copy assignment operator for thrust::transform_iterator

[zkhatami]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Type of Bug

Compile-time Error

Component

Thrust

Describe the bug

The NVC++ stdpar fails to generate a default copy assignment operator for thrust::transform_iterator if the function object it contains is not copyable. For example, for this test case:

#include <algorithm>
#include <execution>
#include <vector>

class A {
  public:
   double* begin() { return m_v.data(); }
   double* v_end() { return m_v.data() + m_v.size(); }
   
  private:
   std::vector<double> m_v ;
} ;

void test(A &A) {
  if (std::any_of(std::execution::par, A.begin(), A.v_end(),
                  [](double v) { return v < double(0.0); })) {
  }
}

The nvc++ stdpar fails with cannot be referenced -- it is a deleted function:

nvc++ -stdpar --c++17 test.cpp

thrust/system/cuda/detail/find.h", line 134: error: function "thrust::THRUST_300000_SM_70_NVHPC_NS::zip_iterator<IteratorTuple>::operator=(const thrust::THRUST_300000_SM_70_NVHPC_NS::zip_iterator<cuda::std::__4::tuple<thrust::THRUST_300000_SM_70_NVHPC_NS::transform_iterator<lambda [](double)->bool, double *, bool, bool>, thrust::THRUST_300000_SM_70_NVHPC_NS::counting_iterator<std::ptrdiff_t, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default>>> &) [with IteratorTuple=cuda::std::__4::tuple<thrust::THRUST_300000_SM_70_NVHPC_NS::transform_iterator<lambda [](double)->bool, double *, bool, bool>, thrust::THRUST_300000_SM_70_NVHPC_NS::counting_iterator<std::ptrdiff_t, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default>>]" (declared implicitly) cannot be referenced -- it is a deleted function
        interval_end = end;
                     ^

This issue arises because lambdas in C++17 have a deleted copy assignment operator, causing the thrust::transform_iterator to become non-copy assignable.
From https://timsong-cpp.github.io/cppwp/n4659/expr.prim.lambda#closure-11:
The closure type associated with a lambda-expression has no default constructor and a deleted copy assignment operator.

This test has started failing after this CCCL commit that replaces the custom copy assignment operator for thrust::transform_iterator with = default:
8da3ace

How to Reproduce

To compile the test with:

nvc++ -stdpar --c++17 test.cpp

Expected behavior

The NVC++ stdpar fails with:

thrust/system/cuda/detail/find.h", line 134: error: function "thrust::THRUST_300000_SM_70_NVHPC_NS::zip_iterator<IteratorTuple>::operator=(const thrust::THRUST_300000_SM_70_NVHPC_NS::zip_iterator<cuda::std::__4::tuple<thrust::THRUST_300000_SM_70_NVHPC_NS::transform_iterator<lambda [](double)->bool, double *, bool, bool>, thrust::THRUST_300000_SM_70_NVHPC_NS::counting_iterator<std::ptrdiff_t, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default>>> &) [with IteratorTuple=cuda::std::__4::tuple<thrust::THRUST_300000_SM_70_NVHPC_NS::transform_iterator<lambda [](double)->bool, double *, bool, bool>, thrust::THRUST_300000_SM_70_NVHPC_NS::counting_iterator<std::ptrdiff_t, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default, thrust::THRUST_300000_SM_70_NVHPC_NS::use_default>>]" (declared implicitly) cannot be referenced -- it is a deleted function
        interval_end = end;
                     ^

Reproduction link

No response

Operating System

No response

nvidia-smi output

No response

NVCC version

No response

[bernhardmgruber]

This for reporting this! We have a fix on this PR #3503. I pulled it out for you: #3542