A design discussion on 0008 surfaced four refinements; this records them
in the exploratory model. Still design exploration, not a spec commitment.
- §3.4 (new): the keywords are adjectival, not verbal. `own`/`borrow`
are acquisition verbs — native on a parameter (the callee acquires),
backwards on a return (the callee disposes; §3.1's own text switches
feet between the two readings). Naming the mode adjectivally
(`owned`/`borrowed`) describes the value the receiver holds and is
position-independent, strengthening §3's uniformity rather than
breaking it. Carries a safety stake, not only readability: a wrong
`own` is the double-free (§6), and the verb form is a mis-annotation
pump pointed that way. Notes the corroborating `ret_mode: ParamMode`
type-name smell (a return mode is a covariant promise, not a
contravariant param demand).
- §4.4: "fixed modes suffice" is contingent on the point-free cut, not a
standalone theorem. Adds the structural discriminator — today's HOFs
control both ends of their seam, so the seam mode is determinate; only
the wire-two-black-boxes kind (point-free) needs a mode variable.
- §5.1–5.3 (new): a tuple question exposed that `ret_mode` is flat but
ownership is a tree over the type — a single top-level `Own` on a
mixed Pair (owned field + borrowed field) decs borrowed data on drop.
Resolved to regime A (borrows may not escape into an escaping heap
structure → transitive ownership → flat `ret_mode` sound), not a
per-field mode tree (regime B = lifetimes). For compound returns,
verification is constitutive of the flat representation's meaning, not
a separable phase — sharpening Q2 to "must" there. Multi-return is the
ownership-honest return path (flat per-position modes, no reachability
pass) but does not subsume the typed boxed aggregate; the boxing point
is the ownership commit.
- §7: Q2 sharpened (compound returns force it), Q3 rewritten (adjectival
keywords + the pre-cutover timing, since a post-cutover rename is a
second irreversible hash reset), Q4 added (multi-return adoption);
resolved-footer extended with regime A and multi-return≠tuple.
- §8 (new): relation to Rust. Concedes the primitive-level convergence
(own/borrow ≈ move/borrow, regime A ≈ Rust's escape rule, unboxed
product ≈ tuple, RC ≈ Rc/Arc), then names what AILang drops and why:
no lifetime polymorphism (the point-free cut removes the pressure that
makes Rust carry it), no `&mut`/shared-XOR-mutable (no shared mutable
refs; mutation rides uniqueness, the Clean lineage), no elision (§2's
no-defaults is the opposite of Rust's elision). Scoped to the
totality-relevant divergences; the broader memory-model lineage is
cross-referenced to 0004 rather than duplicated.
Brummel
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