§4.4's heritage rule, emitted: the base is a declaration this run writes as an interface, so the derived type upcasts to it. Its members are declared again beside the `inherit` - F# admits the redeclaration - which is what keeps `Create` and the member list exact when a *second* base is not inheritable.

A base that names something, but not something this run declares as an interface: a `Fable.Core.JS.*` or `Browser.Types.*` binding, a referenced group's templated name, an abbreviation over a non-object type. `inherit` on a non-interface is FS0887, and this run cannot prove which of those a foreign name is, so its members are flattened.

A base that reaches this declaration again through the inherit graph. TypeScript has no cyclic heritage, but two type ids can share one F# name, so the graph is checked rather than assumed: `inherit` here is FS0954, so the base stays flattened.

A constructor object declared as an interface of its own (§4.4): F# has no first-class type of a class object, so `typeof Request` at a member position reads as a named declaration whose construct signatures are `[]` `Create` members and whose properties are the class's statics.