[class.prop] standard-layout class type requirements are hard to read

[Eisenwave]

I find that https://eel.is/c++draft/class.prop#2.7 is pretty hard to read in its current state:

draft/source/classes.tex

Lines 208 to 230 in 0ca05d2

	\begin{itemize}
	\item If \tcode{X} is a non-union class type with no non-static data members,
	the set $M(\mathtt{X})$ is empty.
	\item If \tcode{X} is a non-union class type with a non-static data
	member of type $\mathtt{X}_0$
	that is either of zero size or
	is the first non-static data member of \tcode{X}
	(where said member may be an anonymous union),
	the set $M(\mathtt{X})$ consists of $\mathtt{X}_0$ and the elements of
	$M(\mathtt{X}_0)$.
	\item If \tcode{X} is a union type, the set $M(\mathtt{X})$ is
	the union of all $M(\mathtt{U}_i)$ and the set containing all $\mathtt{U}_i$,
	where each $\mathtt{U}_i$ is the type of the $i^\text{th}$ non-static data member
	of \tcode{X}.
	\item If \tcode{X} is an array type with element type $\mathtt{X}_e$,
	the set $M(\mathtt{X})$ consists of $\mathtt{X}_e$
	and the elements of $M(\mathtt{X}_e)$.
	\item If \tcode{X} is a non-class, non-array type, the set $M(\mathtt{X})$ is empty.
	\end{itemize}

For starters, we can replace the first and last bullet like:

-\item If \tcode{X} is a non-union class type with no non-static data members, 
-the set $M(\mathtt{X})$ is empty. 
 [...]
-\item If \tcode{X} is a non-class, non-array type, the set $M(\mathtt{X})$ is empty.
+Otherwise, the set $M(\mathtt{X})$ is empty.

I may draft up an actual PR for this soon, but I'm still pondering on how to fully simplify this.

[Eisenwave]

Another optimization opportunity:

-has no element of the set M(S) of types as a base class
+has no base class in the set M(S) of types

[Eisenwave]

It may also be helpful to simply use a good name for M(X) rather than having a note explain the intent. Something like

has none if its zero-offset types as a base class, where the zero-offset types of a type X are defined as follows:

Then we could also delete https://eel.is/c++draft/class.prop#note-1

[Eisenwave]

Lénárd Szolnoki noted that CWG2736 is making changes in the same area.