Provide a new alias for Any, dedicated for use as a placeholder, thus reserving Any for situations when truly every type is acceptable.
When adding type annotations to code that was previously untyped, it's often useful to do so in stages. A common early step is to use Any liberally to avoid getting stuck figuring out the "best" type for a Var. (For example, see this pull request, in which clojure.zip/zipper is given the type [Any Any Any Any -> (Vec Any)].)
The problem is that there's no way to tell whether a given occurrence of Any is functioning as a temporary placeholder, or whether it's expressing the fact that truly every value is acceptable.
I propose a new alias for Any that will enable users to distinguish between these two usages. I don't feel strongly about the name of the alias, but in the absence of other suggestions I nominate Dunno because it concisely expresses the phrase "I don't know".
Unclear how to proceed.
Cool idea. At least in the core library, the annotations should be "safe", that zipper annotation looks too permissive to me.
Perhaps we need a clojure.core.typed.scratch namespace for dirty transitions from untyped to typed.
A possible further enhancement would be trivial TFn (or even a no-op macro) for making temporary types that are more specific than Any but still indicate the need for further refinement. I’ve been using Approx in my own work.