The struct/class split, written down before anything is built on it. A struct
stays a fixed-layout value with C's layout, which is what keeps the FFI, SoA and
wasm stories intact; a class is a separate kind with identity, metadata and an
implementation-defined representation, for the long-lived gameplay objects that
want to change shape while the program is running.
The tagline loses "no GC" for "no mandatory GC", because a small collector
confined to class instances is now an option rather than a contradiction. CLOS
goes from a flat non-goal to a bounded one: the metaclasses, method combination
and arbitrary change-class are out; exact-class single dispatch and an explicit
frame-boundary migration are in.
Migration is eager and explicit rather than CLOS's lazy-on-access, which would
put a check on every slot read. Class identity is stable and layouts are
numbered, the same shape as the function versions the hot reload section grew.
Nothing is frozen and nothing is to be built until struct, Handle and reload
semantics are working.
spec-memory.md drops (set (get m k) v) from the assignable forms: a map has an
upsert of its own, put, which either inserts or replaces, so there is no store
into a lookup - and an absent entry has no location to store into anyway.
The compiler still parsed it into an Ast.Pkey and refused it downstream as
unimplemented, milestone 6, which is the wrong reason for something that is
never arriving. The place form is gone from ast, tast, load, check and emit,
and the parser refuses the shape where it is written, with the reason and a
pointer to put.
