On Mar 26, 2009, at 22:44, srader wrote:
> When I type the following in at the REPL:
>
> (def foo (ref {} :meta {:type :t}))
>
> and then try to print it, I get the following error:
>
> java.lang.ClassCastException: clojure.lang.Ref (NO_SOURCE_FILE:0)
> [Thrown class clojure.lang.Compiler$CompilerException]
>
> Is this a bug?
I'd say yes. Here's what happens: Typing "foo" at the REPL causes a
call to clojure.core/print-method. This is a multimethod that
dispatches on the result of clojure.core/type, which is the value of
the :type tag in the metadata if there is one. Since there is no
implementation for type :t, the default implementation is called,
which is:
(defmethod print-method :default [o, #^Writer w]
(print-method (vary-meta o #(dissoc % :type)) w))
It is the call to vary-meta that fails for a ref.
Konrad.
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