Unexpected TypeNode kind: OptionalType

[agilob]

I'm getting 100s of

❯ dart_js_facade_gen http.d.ts
http.d.ts:299:51: Unexpected TypeNode kind: OptionalType
http.d.ts:299:51: Internal error. Generate null type name.
http.d.ts:299:74: Unexpected TypeNode kind: OptionalType
http.d.ts:299:74: Internal error. Generate null type name.
http.d.ts:299:74: Unexpected TypeNode kind: OptionalType
http.d.ts:299:74: Internal error. Generate null type name.
http.d.ts:299:74: Unexpected TypeNode kind: OptionalType

Line 299 is

export type ArrayBatchRequest = [ string, string, (RequestBody | null)?, (Params | null)? ];

Change to

export type ArrayBatchRequest = [ string, string, RequestBody, Params];

allows transpilation of the file.

trying to convert 0.28.3 of @types/k6

dart_js_facade_gen produces no new files