C#: the FileEntity hierarchy, copy constructors — and the honest answer on generic entities

[skarndev]

The second consumer-feedback round, one question at a time. Rides skarndev/welder-csharp#3 (pinned at 772e6c9) — merge that first.

1. ADT<ClientVersion> generics — assessed, and declined

C# cannot faithfully mimic the C++ value-templated interface: generics take types, not values (no non-type template parameters), and one generic definition carries one member set where ADT<V> instantiations genuinely differ per range (version-gated members, retyped members). Faking it with 11 era marker types over the 5 real layouts would also split type identity — ADT<Mop> ≠ ADT<Legion> despite being one native class — breaking is-checks, equality, and the family dispatch. The hierarchy below delivers the intent (version-agnostic, statically-typed common surface) the way C# actually favors.

2. The hierarchy: Formats.FileEntity

Every file-level entity — the six family bases and BLP — now derives Formats.FileEntity. With welder-csharp's new multi-level family surfaces, the root auto-hoists exactly the contract every child hierarchy binds: Validate() and EnsureValid(), dispatching format-then-version through one FileEntity-typed reference. Read/Write stay on the family bases — ADT's alpha parameter breaks uniformity, and the intersection excludes them automatically rather than by hand list.

The build refused to paper over two real pre-existing gaps, both now fixed at the right layer:

• Single-range families had no surface at all (Skeleton, WDTOcclusion, WDTParticulates — the rod's old two-child minimum). Fixed upstream; Skeleton.ForVersion(...) results finally carry members.
• The WDT assembly was the one file entity with no validate()/ensure_valid() in C++. Added: a compound over the main file and every engaged satellite (root/occlusion/lights/fogs/particulates member paths), mirroring WMO's; the validation-contracts docs page picks it up automatically.

3. Copy constructors + Dispose

new ADTWotlk(other) — the BCL's own copy idiom — replaces Clone() everywhere a C++ copy constructor is admitted. Dispose stays and now documents itself as optional deterministic release (the SafeHandle finalizer frees native memory on collection; using makes it prompt) — the C# answer to "proper destructor" is that the destructor already exists.

Also: the BLP class welds as BLP for C# (the dotnet style had coerced it to Blp; Python always spelled BLP) — the last straggler from the round-1 acronym directive.

Verified

Guide gains "One root above the families"; FamilySurfaceTests locks the heterogeneous WMO+BLP Validate loop, the Read exclusion, and the copy-ctor surface. Full native rebuild + dotnet test: 34/34.

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