Consider adding linter to warn about duplicate names in function/macro parameter lists

[jafingerhut]

It should not warn about duplicate names that begin with '_', since those by convention are for ignored parameters, but something like this should warn:

(defn foo [a a a]
  (+ a a))

I don't know yet how tricky this might get with destructuring in arg lists.

Suggested here (and perhaps in other CLJ tickets as well, not sure): https://dev.clojure.org/jira/browse/CLJ-2293

[jafingerhut]

Not exactly a duplicate of this issue, but related: #225

Catching the example in the previous comment is a simpler thing to do.

Catching duplicated names anywhere in any sequential or associative destructuring in a defn, defn-, or fn arg vector would be more useful to Eastwood users than a check that only caught such duplicate names in the absence of destructuring.

[slipset]

This seems to be caught by redefd-vars in 2.7.0-SNAPSHOT

[vemv]

This seems to be caught by redefd-vars in 2.7.0-SNAPSHOT

Indeed:

duplicate-params: Local name `a` occurs multiple times in the same argument vector.