Fix cross-namespace defmethod: Unknown symbol on compile

[dankinsoid]

Bug

Any defmethod extending a multimethod defmulti'd in a different namespace fails to compile:

;; repro/multi.cljc
(ns repro.multi)
(defmulti kind :type)
(defmethod kind :same-ns [_] "same-ns")

;; repro/ext.cljc
(ns repro.ext
  (:require [repro.multi :as multi]))
(defmethod multi/kind :cross-ns [_] "cross-ns")

Unknown symbol: multi$SLASH_kind1jgmz0t (no source location)

Reproduced on current master (178e4fb) with a fresh (uncached) compile of a plain :kind :dart project. Note that a warm .clojuredart cache can mask the failure, which may be why this survives day-to-day incremental use.

Root cause

expand-method-impl rebuilds the dispatch table from (keys contributions) — the bare synthetic method-class names. emit-contribute* keys contributions by that bare name and stores the relocatable ($lib:-qualified, via relocatable-class-name) name as the value, keyed by contributing namespace:

contributions ; {bare-cname {contributing-ns relocatable-cname}}

A bare name only resolves while compiling the namespace that defined the method class. For a same-namespace defmethod that happens to be the multimethod's own namespace, so it works; for a cross-namespace one, the multimethod's namespace can't resolve it. The emitted table makes this visible — the same-ns entry is resolved, the cross-ns one isn't:

(-> {} transient ((kind1r4nwxi)) ((multi$SLASH_kind1jgmz0t)) persistent!)

Protocol extensions already handle this correctly by reading the relocatable names out of the contribution values ((vals exts) in the extensions expansion).

Fix

Build the table from the contribution values instead:

~@(for [cname (mapcat vals (vals contributions))] ...)

After the fix the repro compiles and both dispatches work at runtime (same-ns / cross-ns both print) — same-namespace methods keep working because relocatable names resolve locally too, same as for protocols.