scriptc

Known compiler bug (v0.3.0, issue #963). A computed-key write anywhere on a generic class instance, e.g. (obj as any)[key] = fn with a non-literal key, makes the method-name census demote that class's methods into prototypeMethodAccesses. The lowered code then reads the per-instance dynamic property bag with no dyn.hasKey guard, and classPrototypeData returns null for generic/generic-instance classes, so there is no prototype fallback: the bag read yields undefined and the call throws. Non-generic classes are unaffected because they get a prototype-data helper.

Workarounds until the compiler fix lands:
1. Eliminate dynamic-key writes on generic class instances — store external metadata in a separate Map/side table or use literal property assignments instead of obj[expr] = value.
2. If feasible, drop the type parameter (use a concrete type instead of Ctx<T>) so the class compiles through the non-generic path, which builds the prototype-data helper and resolves methods correctly.

Compiler-side fix directions under discussion: emit prototype data for generic instances so the bag read has a fallback, or retain the dyn.hasKey guard for methods of generic classes so reads fall back to the static method.

SC1090 means the compiler cannot statically prove the receiver's runtime class, which is required because generic methods dispatch statically. This happens when an object passes through any and is cast back to an interface (e.g., const restored = erased as GenericIdentity; restored.id(42)). This pattern is not supported yet (feature request #905). Workarounds: (1) Call the generic method directly on the original typed object before it is erased to any — direct calls through the original object are supported. (2) For class instances, bind the receiver to a const initialized with its new expression so the class is provable: const r: GenericIdentity = new C(...). Note: there is currently no workaround for generic arrow-function properties on object literals that must round-trip through any or type-erased storage.