CTAD bug in vector length

[joeatodd]

Describe the bug
Swizzled vector types can't be passed directly to length() because detail::is_gengeohalf<T>::value is false for these types.

From this StackOverflow question.

To Reproduce

#define SYCL_SIMPLE_SWIZZLES
#include <CL/sycl.hpp>

using namespace sycl;

int main(){
  float3 myVec{1.0, 0.0, 2.0};
  auto len = length(myVec.zy());
}

The above code fails to compile because it cant deduce typename T of length (should be float2?) If one instead has

auto len = length<float2>(myVec.zy());

it works fine.

Additional context

length() is defined in builtins.hpp:

// float length (gengeofloat p)
template <typename T,
          typename = detail::enable_if_t<detail::is_gengeofloat<T>::value, T>>
float length(T p) __NOEXC {
  return __sycl_std::__invoke_length<float>(p);
}

and detail::is_gengeofloat<T> is only true for type_list<float, vec<float, 1>, vec<float, 2>, vec<float, 3>, vec<float, 4>>.

I'm not sure if the solution is to include the SwizzleOp types in geo_float_list or to define a specialization for length etc for SwizzleOp types, but as the StackOverflow OP points out, this somewhat defeats the purpose of swizzle convenience operations.

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[KornevNikita]

Re-opening as the patch was reverted. But #10198 should solve it.