Type piracy in `convert` and constructors for basic Julia types

[KristofferC]

The stuff in

Random123.jl/src/aesni_common.jl

Lines 7 to 16 in 195d1ee

	const __m128i = NTuple{2, VecElement{UInt64}}
	Base.convert(::Type{__m128i}, x::UInt128) = unsafe_load(Ptr{__m128i}(pointer_from_objref(Ref(x))))
	Base.convert(::Type{UInt128}, x::__m128i) = unsafe_load(Ptr{UInt128}(pointer_from_objref(Ref(x))))
	UInt128(x::__m128i) = convert(UInt128, x)
	__m128i(x::UInt128) = convert(__m128i, x)
	Base.convert(::Type{__m128i}, x::Union{Signed, Unsigned}) = convert(__m128i, UInt128(x))
	Base.convert(::Type{T}, x::__m128i) where T <: Union{Signed, Unsigned} = convert(T, UInt128(x))
	const LITTLE_ENDIAN = ENDIAN_BOM ≡ 0x04030201
	__m128i(hi::UInt64, lo::UInt64) = LITTLE_ENDIAN ? (VecElement(lo), VecElement(hi)) : (VecElement(hi), VecElement(lo))

is type piracy and changes how basic Julia types behave.

You should in general do something like

struct __m128i
    data:: NTuple{2, VecElement{UInt64}}
end

and define functions on that (similar as to how e.g. SIMD.jl does it, https://github.com/eschnett/SIMD.jl/blob/863e12ffd3fc36c4d9257f5332525948d55c9a70/src/simdvec.jl#L1-L3)

[sunoru]

Yes you are right and thanks for pointing it out. I realized this problem once but forgot to fix it. 😢