Unintuitive recursive type error in simple code

[davazp]

The following code fails to type

(lambda () ((:callback *context*) 10))

It infers that the context has to have a :callback field of type function:

{
  :callback (-> .... number a)
}

but what's the full type of that function? the function is called in the same context itself, so the inferred type for the code would be a recursive context.