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

Bool

1. Explicitly convert to float, int, bool vector
2. Implicitly convert to bool vector init
3. Implicitly convert to distinct bool if constant value.

Int

1. Implicitly convert to unsigned counterpart
2. Implicitly convert to float / wider int for simple expressions.
3. Implicitly convert to same int vector init (or any?)
4. Explicitly convert to pointer if pointer sized
5. Explicitly convert to same size int vector, enum with same backing size, bitstruct with same backing size.
6. Explicitly convert to bool, any int or float.
7. Implicitly convert to bool in conditionals.
8. Implicitly convert to any distinct integer. (Same size only?)
9. Implicitly convert to any float/int/distinct float/int if constant value that fits.

Float

1. Implicitly convert to wider float for simple expressions.
2. Implicitly convert to same float vector init (or any?)
3. Explicitly convert to bool, any int or float.
4. Explicitly convert to any distinct float. (Same size only?)
5. Implicitly convert to any float / distinct float constant value that fits.

Non void* pointer

1. Implicitly convert to void* and any.
2. Implicitly convert to an interface if the pointee implements the interface.
3. Explicitly convert to pointer sized int.
4. Implicitly convert to slice if it is a pointer to a vector or array.
5. Explicitly convert to any other pointer.
6. Explicitly convert to any distinct pointer.

void* pointer

1. Implicitly convert to a pointer sized int.
2. Implicitly convert to any other pointer.
3. Explicitly convert to any distinct pointer.
4. Implicitly convert to any distinct pointer if constant value.

Slice

1. Implicitly convert to a pointer of the same type.

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
slice	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