c3c/resources/castrules.md

Some short names:

1. expl - explicit
2. sw/sn - simple widening + subexpression narrowing
3. yes - always allowed
4. explptr - explicit if pointer sized
5. ptrconv - to/from void* is fine, other cast must be explicit
6. saconv - explicit if same element size
7. explbase - explicit to base disregaring sign
8. distel - explicit to same element disregarding distinct
9. inline - implicit if type subtype
10. cond - implicit in cond, explicit otherwise
11. edist - explicit to anything underlying type can convert to, if inline as underlying
12. arve - if array or vec ptr

from, to	bool	int	float	pointer	subarr	vec	bits	distc	array	struct	union	any	fault	enum	typeid
bool	n/a	expl	expl	no	no	expand	no	edist	no	no	no	no	no	no	no
int	cond	sw/sn	always	explptr	no	expand	explbase	edist	no	no	no	no	no	edist	no
float	cond	expl	sw/sn	no	no	expand	no	edist	no	no	no	no	no	no	no
pointer	cond	explptr	no	ptrconv	arve	expand	no	edist	no	no	no	yes	expl	no	expl
subarray	cond	no	no	no	saconv	no	no	edist	no?	no	no	no	no	no	no
vec	cond	no	no	no	no	as base	no	edist	expl	no	no	no	no	no	no
bits	no	explbase	no	no	no	no	no?	edist	explbase	no	no	no	no	no	no
distc	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist	edist
array	no	no	no	no	no	explbase	explbase	edist	distel	no	no	no	no	no	no
struct	inline	inline	inline	inline	inline	inline	inline	edist	inline	inline	inline	inline	inline	inline	inline
union	no	no	no	no	no	no	no	edist	no	no	no	no	no	no	no
any	cond	no	no	expl	no	no	no	edist	no	no	no	n/a	no	no	no
fault	cond	explptr	no	expl	no	no	no	edist	no	no	no	no	anyf	no	no
enum	no	expl	no	no	no	expand	no	edist	no	no	no	no	no	no	no
typeid	cond	no	no	expl	no	no	no	edist	no	no	no	no	no	no	n/a