Nested let-mutable's

[vitvly]

Hi!

Thank you for your open-source work!

I've recently ran into an issue with Proteus, namely that

(let-mutable [a 3
              b (let-mutable [c 1 ]
                  c)]
  b)

will yield

CompilerException java.lang.ClassCastException: java.lang.Long cannot be cast to proteus.Containers$L, compiling:(proteus.clj:123:1)

After macro-expanding it turns out that read-form gets applied twice to c. After some debugging i've figured out how to address the issue by modifying the code of read-form to

(defn- read-form [x]
  (if (not (:tag (meta x)))
    (-> (locals) (find x) key* meta ::read-form)
    nil))

It checks for the presence of :tag in local's metadata, which should only be there if it is being processed by the let-mutable macro at the current level of nesting.

It seems that a corresponding fix to write-form is not necessary.

If the above is correct and there are no stupid mistakes on my part, i can make a pull request.

Thanks again,
Vitaliy.

[ztellman]

It's been a while since I've looked at this code, but that seems like a sane fix to me. If you can open a pull request with some additional test cases, I'd appreciate it.