F.BadInput documentation should include language similar to F.Fatal. The example clearly uses it for control flow, and the current documentation hints at that, but it should be made clear like F.Fatal.

Fuzzing of built-in types (e.g. simple types, maps, arrays) and types which implement the BinaryMarshaler and TextMarshaler interfaces are supported.

That should include corresponding XxxUnmarshaler interfaces or you won't be able to load them back from files; the Implementation section gets that right, which might be a sign of unnecessary duplication. Suggestion: define the concept fuzzable type once, don't repeat.

By the time this proposal makes it to actual docs, definition of fuzzable types should explicitly state that the combination of built-in types with marshalable fields/values/etc are fuzzable too. Right now that is merely implied.

Closing this issue, since discussion will now be at https://golang.org/s/draft-fuzzing-reddit.