`thrust::exclusive_scan` deduces value type from identity value

I ran into a particularly hard-to-spot issue that I would consider a bug ~~in Thrust~~ in the C++ standard 😄 :

```cpp
#include
#include
#include
#include
#include

int main() {
thrust::device_vector vec(3);
vec[0] = std::numeric_limits::max() - 1;
vec[1] = 1;
vec[2] = 0;
thrust::exclusive_scan(vec.begin(), vec.end(), vec.begin(), 0);
std::cout << vec[0] << '\n';
std::cout << vec[1] << '\n';
std::cout << vec[2] << '\n';
}
```

I would expect this to output 0, LONG_MAX - 1 and LONG_MAX, instead it outputs 0, -2, -1.

EDIT: I checked with std::exclusive_scan, and I get the same behavior, but TBH this seems like a really bug-prone specification to me. I would expect the computational type to be derived based on the return type of the associative operation or the iterator types.