Implement in-ns as a function.

[SignSpice]

Please answer the following questions and leave the below in as part of your PR.

• I have read the developer documentation.

• This PR corresponds to an issue with a clear problem statement.
  implement in-ns as function rather than built-in #790

• This PR contains a test to prevent against future regressions

[SignSpice]

Not sure how to go about setting the namespace just yet. WIP

[mraveloarinjaka]

@borkdude

The following test fails:

(= :bar/foo (eval* "(#'clojure.core/in-ns 'bar) ::foo"))

With the start of the stack:

ERROR in (in-ns-test) (core.clj:4739) expected: (= :bar/foo (eval* "(#'clojure.core/in-ns 'bar) ::foo")) actual: clojure.lang.ExceptionInfo: Wrong number of args (1) passed to: namespaces/sci-in-ns at clojure.core$ex_info.invokeStatic (core.clj:4739) clojure.core$ex_info.invoke (core.clj:4739) sci.impl.utils$rethrow_with_location_of_node.invokeStatic (utils.cljc:134) sci.impl.utils$rethrow_with_location_of_node.invoke (utils.cljc:91) sci.impl.interpreter$eval_form.invokeStatic (interpreter.cljc:42) sci.impl.interpreter$eval_form.invoke (interpreter.cljc:15)

Is it something that should be supported by sci?

[borkdude]

@mraveloarinjaka Where did you encounter this behavior in real life?

[mraveloarinjaka]

I was testing whether the issue hyperfiddle/rcf#35 was solved with the latest changes done with this fix.
I believe that sci still chokes at https://github.com/hyperfiddle/rcf/blob/master/src/hyperfiddle/rcf/analyzer.clj#L25

[borkdude]

@mraveloarinjaka I didn't expect this dynamic usage of in-ns via a var, but it can be fixed. Let create a new issue.