feat(core): LambdaDelta part 2 — hygienic macros + multimethods + prelude

[hyperpolymath]

What this is

The language core, completed (spec §3) — the second half of "1 then 2": full macro hygiene, procedural defmacro, multimethods, and a sugar prelude. Builds on the L0 kernel (#35) and notebook host (#36); the kernel/host seam is untouched, so the notebook host inherits all of this for free.

You chose B — full set-of-scopes hygiene now, in one pass — and that's what this is: not the weaker Clojure auto-gensym model.

Full hygiene (and it's genuinely full)

Kohlbecker-style marks, encoded in symbol names. Each macro expansion gets a fresh mark; quasiquote tags the symbols a template introduces with it. Both hygiene properties are implemented and tested:

Property	Test	Result
Introduced bindings never capture	(defmacro m [e] \(let [x 2] ~e)) (let [x 1] (m x))`	1, not 2
Free identifiers are referentially transparent	(defmacro inc [n] \(+ ~n 1)) (let [+ -] (inc 5))`	6, not 4

So the prelude's and/or/if-let use plain v/tmp with no foo# — "macro-introduced bindings never capture… without the author asking" (spec §3), delivered literally.

Mechanics: marked free identifiers fall back to the definition (global) env; special forms and macros dispatch on the base name (so a marked let/if/user-macro in a template still works); Display strips marks so output stays readable.

What's in this PR

• defmacro — procedural transformer over unevaluated forms; gensym, macroexpand, macroexpand-1.
• Multimethods (spec §3, open dispatch — not class-OO): defmulti name dispatch-fn + defmethod name dispatch-val [args] … with :default. Dispatch on any function of the args — e.g. a note's :type:

  (defmulti describe :type)
  (defmethod describe "task" [n] (str "task:" (:title n)))
  (defmethod describe :default [n] "other")

• Prelude (prelude.rs) — hygienic sugar written in λδ itself, loaded at Interp::new(): when unless cond and or -> ->> if-let when-let.

Files

value.rs (mark primitives + MultiMethod + mark-stripping display) · mod.rs (macro/multimethod registries, mark counters, prelude load) · eval.rs (hygiene-aware symbol resolution, base-name dispatch, expand_macro, defmacro/defmulti/defmethod, quasiquote marking) · builtins.rs (gensym/macroexpand) · prelude.rs (new) · tests.rs (11 new tests).

Deliberately deferred

let/fn destructuring; an explicit unhygienic escape hatch (if ever justified); case/match (pattern matching). Each layers on without touching the seam.

Verification

• cargo test — 81 lib tests green (11 new: user macros, both hygiene properties, multimethods, all prelude sugar, gensym, macroexpand) + host + golden + invariants + doc-tests.
• cargo clippy --all-targets -- -D warnings — clean (default and --features wasm).
• cargo fmt --check — clean. Production kernel stays panic-free (Hypatia-clean).

Note: estate governance workflow_audit findings are pre-existing estate policy, out of scope; rust-ci is the gate here.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PAEqVP7Y3bZDhtAaPUTbps

---

Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🔍 Hypatia Security Scan

Findings: 62 issues detected

Severity	Count
🔴 Critical	1
🟠 High	30
🟡 Medium	31

⚠️ Action Required: Critical security issues found!

View findings

[
  {
    "reason": "Issue in scorecard.yml",
    "type": "missing_workflow",
    "file": "scorecard.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Issue in boj-build.yml",
    "type": "missing_timeout_minutes",
    "file": "boj-build.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in casket-pages.yml",
    "type": "missing_timeout_minutes",
    "file": "casket-pages.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in casket-pages.yml",
    "type": "missing_timeout_minutes",
    "file": "casket-pages.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in codeql.yml",
    "type": "missing_timeout_minutes",
    "file": "codeql.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in dogfood-gate.yml",
    "type": "missing_timeout_minutes",
    "file": "dogfood-gate.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in dogfood-gate.yml",
    "type": "missing_timeout_minutes",
    "file": "dogfood-gate.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in dogfood-gate.yml",
    "type": "missing_timeout_minutes",
    "file": "dogfood-gate.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in dogfood-gate.yml",
    "type": "missing_timeout_minutes",
    "file": "dogfood-gate.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Issue in dogfood-gate.yml",
    "type": "missing_timeout_minutes",
    "file": "dogfood-gate.yml",
    "action": "flag",
    "rule_module": "workflow_audit",
    "severity": "medium"
  }
]

Powered by Hypatia Neurosymbolic CI/CD Intelligence