Cloudflare workers-types generation — status & remaining-work map

As of 2026-06-28. Target: @cloudflare/workers-types (latest) generated F#, compiled against Fable.Core + Xantham.Fable.Core. Error count is the Phase-B compile-error total.

Trajectory

The surface went from not compiling at all (≈102 syntax errors → fully parsing) to ~2,868 semantic errors, with every catastrophic correctness defect resolved.

Milestone	Errors
Syntax dam broke (output first parses)	9,880
After the structural/semantic fixes below	3,204
lib.es map (#4)	3,054
inherit-non-interface (drop inherit exn/obj)	2,972
named Array<T> → ResizeArray (staged, uncommitted)	2,868

Committed fixes (correctness-critical)

• string-collapse: string no longer renders as D1SessionBookmark (was 2,094×).
• type-parameter constraints (when 'T :> X); EmitProperty not CompiledName on abstract members (FS0755, was 6,498); Array/T[] → ResizeArray; emit U10+ erased unions; inherit type-arg fix; coordinated alias self-reference fix (IR self-refs 332 → 0); lib.es map (Error→exn, PromiseLike→Promise, iterators→seq, …); drop non-interface heritage bases.

Staged (uncommitted, verified, ready to commit)

• Render.fs: named lib Array<T> → ResizeArray<'T> via a typescript-source stdlib substitution (safety-gated by the substitution map). 185 tests pass, no crash. −104 errors.

Remaining ~2,868 errors — classified

Class	~count	What it is	Tractability
*Response/Request/RequestInit/WebSocket/QueuingStrategy undefined*	~340	workers-types' OWN globals (source typescript) dropped to ref-only by the source-ignore gate	FIXED (Fix A, staged) — globals now emitted at top level; see path-system-pass-findings.md. Payoff masked by B + dup-members below.
*Type/Format/ToolCalls/Role/FunctionCall/… undefined*	large share of FS0039	hoisted nested types deduped by ResolvedType; references named per-property dangle	root cause PINNED, not surgical — TypeStore + render cache both keyed by ResolvedType; heterogeneous sharing (pop≡length) makes redirect wrong (+1046). Needs encoder-side distinct keys. See path-system-pass-findings.md.
duplicate members from declaration merging	~60+	Response etc. emit url/type/status 2× (merged lib + workers decls) → FS0035x/FS0663	new — surfaced by Fix A; dedup members by name at render
FS0033 typed arrays (Uint8Array<X>, ArrayBufferView<X>, Float32Array<X>)	~130	generic in TS, non-generic in Fable.Core.JS — needs the spurious arg dropped	attempted: dropping the arg traded ~300 FS0033 for ~140 FS0039 (the element type is load-bearing somewhere) + %A debug spam → reverted. Not yet clean.
FS0953 cyclic aliases	170	type X = U2<X,X> residual; splits encoder-corrupt (Array<spurious> bodies) + anonymous-union limitation	Step-2, deferred-documented (see alias-self-reference-followup.md)
FS0663/0883/0698/0660/0035	~230	bogus typar constraints / structural-construct issues from the above families	mostly downstream of the path/alias work

The strategic read

Clean, isolated wins are thinning. The two largest remaining levers — the typescript-source global placement (~340) and the dropped hoisted nested types (#3) — both live in the path / module-resolution subsystem (transient→anchored path localisation, TypeStore dedup keyed by ResolvedType). Four focused attempts on that subsystem each produced double-grafts or crashes; it resists surgical fixes and likely needs a dedicated, deeper effort (possibly with an encoder-side component, since some alias/array bodies are genuinely corrupt in the IR).

Recommendation: the remaining high-value work is a dedicated path-system pass (global placement + nested-type hoisting), treated as its own project with proper architectural design rather than incremental surgical attempts. The typed-array drop-arg is a smaller separate item once the element-type dependency is understood. Everything catastrophic is already fixed and committed; what remains is well-formedness polish concentrated in one subsystem.

Detailed root-cause notes: docs/alias-self-reference-followup.md.