Refer OpenCL Spec 1.2

Section 6.2.3
Explicit conversions may be performed using the
convert_destType(sourceType)
suite of functions. These provide a full set of type conversions between supported types (see
sections 6.1.1, 6.1.2 and 6.1.3) except for the following types: bool, half, size_t,
ptrdiff_t, intptr_t, uintptr_t, and void

Section 6.2.3.1
Conversions are available for the following scalar types: char, uchar, short, ushort,
int, uint, long, ulong, float, and built-in vector types derived therefrom.

There are datatypes like
double,
image2d_t
image3d_t
image2d_array_t
image1d_t
image1d_buffer_t
image1d_array_t
sampler_t
event_t
Which are covered in section 6.2.3, but not in 6.2.3.1. What is expected of these datatypes?