giles 2981a479e8 reflective: extract class-chain.sx — Smalltalk + CLOS method dispatch share parent-walk ...

lib/guest/reflective/class-chain.sx — class inheritance walker with
adapter cfg for single-parent (Smalltalk) and multi-parent (CLOS)
hierarchies. Three primitives:

- refl-class-chain-find-with CFG CN PROBE
    DFS through parents, returns first non-nil probe result.
    Smalltalk method lookup uses this.

- refl-class-chain-depth-with CFG CN ANCESTOR
    Min hop distance via any parent path, or nil if unreachable.
    CLOS method specificity uses this.

- refl-class-chain-ancestors-with CFG CN
    Flat DFS-ordered list of all reachable ancestor names.

Adapter cfg has two keys: :parents-of (CN → list of parent names,
possibly empty) and :class? (predicate; short-circuits walk on
non-existent class names mid-chain).

Migrations:
- lib/smalltalk/runtime.sx: st-method-lookup-walk now a 9-line
  thin probe through the kit (was 20 lines of inline recursion);
  st-class-cfg wraps the single-parent :superclass field into a
  1-element list for the cfg.

- lib/common-lisp/clos.sx: clos-specificity is a one-line wrapper
  around refl-class-chain-depth-with (was 28 lines); clos-class-cfg
  reads the multi-parent :parents field.

Both consumers green:
- Smalltalk: 847/847 (unchanged)
- CL: 222/240 (unchanged baseline; 18 pre-existing failures, all
  in stdlib functions like cl-set-memberp, unrelated to CLOS).

This is the second extracted reflective kit (env.sx was first).
The adapter-cfg pattern continues to bridge structurally divergent
consumers (Smalltalk single-inheritance vs CLOS multiple-inheritance
with method-precedence distance) via a uniform :parents-of callback.

2026-05-12 21:09:07 +00:00

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