On Tue, Feb 08, 2011 at 09:01:38AM -0500, Stuart Halloway wrote:
> Please let us know when you get a misleading error message from a
> macroexpansion, so we can make it better. Or contribute a patch along the
> lines
> of [2].
Here's another error message that really threw me off for a while.
I have some code that looks like this:
(let [[x y] (nth @my-atom z)]
...)
Which occasionally failed with:
java.lang.UnsupportedOperationException: nth not supported on this type:
Float
at clojure.lang.RT.nthFrom(RT.java:815) ~[clojure-1.2.0.jar:na]
at clojure.lang.RT.nth(RT.java:765) ~[clojure-1.2.0.jar:na]
I tried to figure out how a single float could have ended up in that
atom and why I couldn't catch it by checking for `(coll? @my-atom)`.
After a while I found out that `@my-atom` indeed contained a
collection -- a collection of floats -- and that the exception was
thrown by the destructuring.
An error message something like this would have been much more helpful:
Can't destructure `(nth @my-atom z)` to `[x y]`: expected a
collection with 2 or more items but got `Float`.
--
Timo
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