Providing a non-Int64 N parameter to NTuple within a struct does not throw error

[mkitti]

I provide a Int8 or UInt8 value as the first parameter to a NTuple within a struct, I get a Union{} for its type with fieldtype. I would have expected an error similar to the one received when trying to construct a NTuple directly.

julia> struct S{P}
           x::NTuple{P,UInt32}
       end

julia> fieldtype(S{2},1)
Tuple{UInt32, UInt32}

julia> fieldtype(S{0x2},1)
Union{}

julia> fieldtype(S{Int8(2)},1)
Union{}

julia> fieldtype(S{Int16(2)},1)
Union{}

julia> fieldtype(S{Int32(2)},1)
Union{}

julia> fieldtype(S{Int64(2)},1)
Tuple{UInt32, UInt32}

julia> fieldtype(S{Int128(2)},1)
Union{}

julia> NTuple{0x2, UInt32}
ERROR: TypeError: in Vararg, in count, expected Int64, got a value of type UInt8
Stacktrace:
 [1] top-level scope
   @ REPL[15]:1

[vtjnash]

fieldtypes are not part of the identity of a type, so construction of it is legal, though this may be a bit of a surprise that could be better documented to be google-searchable (c.f. #31877)

[mkitti]

Could we just make NTuple{0x2, UInt32} work somehow? We could convert 0x2 to an Int and then continue.