Also discussed at https://groups.google.com/d/topic/clojure/e6UhXVny8Xc/discussion

Per Rich, "The policy is: = includes the type and .equals doesn't. In this way records can still be proper j.u.Maps and = remains most useful for records (e.g. including type)."

On a related note:

http://dev.clojure.org/display/doc/Enhanced+Primitive+Support?focusedCommentId=1573146#comment-1573146

Regarding "hash maps and sets now use = for keys ... will use stricter .equals when calling through java.util interfaces":

Note that "=" is actually stricter than ".equals" for record types currently, because it includes type information.

This has important consequences for how (and whether) hash maps and sets actually obey the java.util interfaces.

For instance, if

(defrecord P []), ...

what should (.get {(P.) 1 (Q.) 2} (Q.)) return? How about if we .get an element of a third type (R.)?

In a similar vein, this behavior seems confusing at best:

user=> (java.util.HashMap. {(P.) 1 (Q.) 2})
#<HashMap {user.P@0=2}>

Open question:

• the phrase "type-independent" is confusing. It is intended to talk about concrete numeric and collection types, but I can see why it gets confusing with records. Need an idea for two different terms here (and define them someplace). If somebody has one, please add it to this ticket.

Non-issues:

• = and .equals are not and will not be the same. The whole point is to avoid Java's broken semantics (=) while providing an interop formula for those who need it (.equals)
• Any types can collide as hash keys.

Any thoughts on the open questions part Rich?

I think the following is better:

monospaced
In addition, defrecord will define type-and-value-based =,
and will defined Java .hashCode and .equals consistent with the
contract for java.util.Map.
monospaced

But I don't want to hold release for discussion, so bumping this to approved backlog for further bikeshedding.

Better yet, let's just agreed on my prose and call this done.