template FieldTypeTuple(S) in std.traits

[pc]

1. Are the types guaranteed to be in the same order as the definition?

struct S1 {int a; float f} can be intialized with S1(10, 10.5), implying a constructor that is based on the lexical order in the definition? 

Will FieldTypeTuple!(S1), always give me Tuple!(int, float)? 

Would the answer be the same if S1 were a class?

2. The description of "Template RepresentationTypeTuple(T...)" states:

    Get the primitive types of the fields of a struct or class, in topological order. 

Is this the lexical order in the code or how they are laid out when compiled or what?

Thanks