smalltalk: method-lookup cache + 10 tests

plans/smalltalk-on-sx.md

@@ -58,7 +58,7 @@ Core mapping:
 ### Phase 2 — object model + sequential eval
 - [x] Class table + bootstrap (`lib/smalltalk/runtime.sx`): canonical hierarchy installed (`Object`, `Behavior`, `ClassDescription`, `Class`, `Metaclass`, `UndefinedObject`, `Boolean`/`True`/`False`, `Magnitude`/`Number`/`Integer`/`SmallInteger`/`Float`/`Character`, `Collection`/`SequenceableCollection`/`ArrayedCollection`/`Array`/`String`/`Symbol`/`OrderedCollection`/`Dictionary`, `BlockClosure`). User class definition via `st-class-define!`, methods via `st-class-add-method!` (stamps `:defining-class` for super), method lookup walks chain, ivars accumulated through superclass chain, native SX value types map to Smalltalk classes via `st-class-of`.
 - [x] `smalltalk-eval-ast` (`lib/smalltalk/eval.sx`): all literal kinds, ident resolution (locals → ivars → class refs), self/super/thisContext, assignment (locals or ivars, mutating), message send, cascade, sequence, and ^return via a sentinel marker (proper continuation-based escape is the Phase 3 showcase). Frames carry a parent chain so blocks close over outer locals. Primitive method tables for SmallInteger/Float, String/Symbol, Boolean, UndefinedObject, Array, BlockClosure (value/value:/whileTrue:/etc.), and class-side `new`/`name`/etc. Also satisfies "30+ tests" — 60 eval tests.
-- [ ] Method lookup: walk class → superclass; cache hit-class on `(class, selector)`
+- [x] Method lookup: walk class → superclass already in `st-method-lookup-walk`; new cached wrapper `st-method-lookup` keys on `(class, selector, side)` and stores `:not-found` for negative results so DNU paths don't re-walk. Cache invalidates on `st-class-define!`, `st-class-add-method!`, `st-class-add-class-method!`, `st-class-remove-method!`, and full bootstrap. Stats helpers `st-method-cache-stats` / `st-method-cache-reset-stats!` for tests + later debugging.
 - [ ] `doesNotUnderstand:` fallback constructing `Message` object
 - [ ] `super` send (lookup starts at superclass of *defining* class, not receiver class)
 - [x] 30+ tests in `lib/smalltalk/tests/eval.sx` (60 tests, covering literals through user-class method dispatch with cascades and closures)
@@ -108,6 +108,7 @@ Core mapping:
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-25: method-lookup cache (`st-method-cache` keyed by `class|selector|side`, stores `:not-found` for misses). Invalidation on define/add/remove + bootstrap. `st-class-remove-method!` added. Stats helpers + 10 cache tests; 255/255 total.
 - 2026-04-25: `smalltalk-eval-ast` + 60 eval tests (`lib/smalltalk/eval.sx`, `lib/smalltalk/tests/eval.sx`). Frame chain with mutable locals/ivars (via `dict-set!`), full literal eval, send dispatch (user methods + native primitive tables for Number/String/Boolean/Nil/Array/Block/Class), block closures, while/to:do:, cascades returning last, sentinel-based `^return`. User Point class round-trip works including `+` returning a fresh point. 245/245 total.
 - 2026-04-25: class table + bootstrap (`lib/smalltalk/runtime.sx`, `lib/smalltalk/tests/runtime.sx`). Canonical hierarchy, type→class mapping for native SX values, instance construction, ivar inheritance, method install with `:defining-class` stamp, instance- and class-side method lookup walking the superclass chain. 54 new tests, 185/185 total.
 - 2026-04-25: chunk-stream parser + pragmas + 21 chunk/pragma tests (`lib/smalltalk/tests/parse_chunks.sx`). `st-read-chunks` (with `!!` doubling), `st-parse-chunks` state machine for `methodsFor:` batches incl. class-side. Pragmas with multiple keyword pairs, signed numeric / string / symbol args, in either pragma-then-temps or temps-then-pragma order. 131/131 tests pass.