cl: Phase 3 conditions + restarts — handler-bind, handler-case, restart-case, 55 tests (123 total runtime)

define-condition with 15-type ANSI hierarchy (condition/error/warning/
simple-error/simple-warning/type-error/arithmetic-error/division-by-zero/
cell-error/unbound-variable/undefined-function/program-error/storage-condition).

cl-condition-of-type? walks the hierarchy; cl-make-condition builds tagged
dicts {:cl-type "cl-condition" :class name :slots {...}}. cl-signal-obj
walks cl-handler-stack for non-unwinding dispatch. cl-handler-case and
cl-restart-case use call/cc escape continuations for unwinding. All stacks
are mutable SX globals (the built-in handler-bind/restart-case only accept
literal AST specs — not computed lists). Key fix: cl-condition-of-type?
captures cl-condition-classes at define-time via let-closure to avoid
free-variable failure through env_merge parent chain.

55 tests in lib/common-lisp/tests/conditions.sx, wired into test.sh.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plans/common-lisp-on-sx.md

@@ -66,14 +66,14 @@ Core mapping:
 - [x] 127 tests in `lib/common-lisp/tests/eval.sx`
 
 ### Phase 3 — conditions + restarts (THE SHOWCASE)
-- [ ] `define-condition` — class hierarchy rooted at `condition`/`error`/`warning`/`simple-error`/`simple-warning`/`type-error`/`arithmetic-error`/`division-by-zero`
-- [ ] `signal`, `error`, `cerror`, `warn` — all walk the handler chain
-- [ ] `handler-bind` — non-unwinding handlers, may decline by returning normally
-- [ ] `handler-case` — unwinding handlers (delcc abort)
-- [ ] `restart-case`, `with-simple-restart`, `restart-bind`
-- [ ] `find-restart`, `invoke-restart`, `invoke-restart-interactively`, `compute-restarts`
-- [ ] `with-condition-restarts` — associate restarts with a specific condition
-- [ ] `*break-on-signals*`, `*debugger-hook*` (basic)
+- [x] `define-condition` — class hierarchy rooted at `condition`/`error`/`warning`/`simple-error`/`simple-warning`/`type-error`/`arithmetic-error`/`division-by-zero`
+- [x] `signal`, `error`, `cerror`, `warn` — all walk the handler chain
+- [x] `handler-bind` — non-unwinding handlers, may decline by returning normally
+- [x] `handler-case` — unwinding handlers (call/cc escape)
+- [x] `restart-case`, `with-simple-restart`, `restart-bind`
+- [x] `find-restart`, `invoke-restart`, `compute-restarts`
+- [x] `with-condition-restarts` — associate restarts with a specific condition
+- [ ] `invoke-restart-interactively`, `*break-on-signals*`, `*debugger-hook*` (basic)
 - [ ] Classic programs in `lib/common-lisp/tests/programs/`:
   - [ ] `restart-demo.lisp` — division with `:use-zero` and `:retry` restarts
   - [ ] `parse-recover.lisp` — parser with skipped-token restart
@@ -124,6 +124,7 @@ data; format for string templating.
 
 _Newest first._
 
+- 2026-05-05: Phase 3 conditions + restarts — `cl-condition-classes` hierarchy (15 types), `cl-condition?`/`cl-condition-of-type?`, `cl-make-condition`, `cl-define-condition`, `cl-signal`/`cl-error`/`cl-warn`/`cl-cerror`, `cl-handler-bind` (non-unwinding), `cl-handler-case` (call/cc escape), `cl-restart-case`/`cl-with-simple-restart`, `cl-find-restart`/`cl-invoke-restart`/`cl-compute-restarts`, `cl-with-condition-restarts`; 55 new tests in `tests/conditions.sx` (123 total runtime tests). Key gotcha: `cl-condition-classes` must be captured at define-time via `let` in `cl-condition-of-type?` — free-variable lookup at call-time fails through env_merge parent chain.
 - 2026-05-05: tagbody + go — cl-go-tag? sentinel; cl-eval-tagbody runs body with tag-index map (keys str-normalised for integer tags); go-tag propagation in cl-eval-body alongside block-return; 11 new tests (151 eval, 323 total green).
 - 2026-05-05: block + return-from — sentinel propagation in cl-eval-body; cl-eval-block catches matching sentinels; BLOCK/RETURN-FROM/RETURN dispatch in cl-eval-list; 13 new tests (140 eval, 312 total green). Parser: CL strings → {:cl-type "string"} dicts.
 - 2026-04-25: Phase 2 eval — 127 tests, 299 total green. `lib/common-lisp/eval.sx`: cl-eval-ast with quote/if/progn/let/let*/flet/labels/setq/setf/function/lambda/the/locally/eval-when; defun/defvar/defparameter/defconstant; built-in arithmetic (+/-/*//, min/max/abs/evenp/oddp), comparisons, predicates, list ops (car/cdr/cons/list/append/reverse/length/nth/first/second/third/rest), string ops, funcall/apply/mapcar. Key gotchas: SX reduce is (reduce fn init list) not (reduce fn list init); CL true literal is t not true; builtins registered in cl-global-env.fns via wrapper dicts for #' syntax.