String temp ids do not work with d/entity function calls

stringtemp.clj

;;google group discussion link https://groups.google.com/forum/#!topic/datomic/m6vSa6CjqjQ
(ns stringtemp.core
  (:import datomic.Util)
  (require [datomic.api :as d]
           [clojure.java.io :as io]))


;;Create the DB
(def db-uri "datomic:dev://localhost:4334/stringtemp")
(d/create-database db-uri)
(def conn (d/connect db-uri))

;; Schema
;[{:db/ident :foo/name
;  :db/valueType :db.type/string
;  :db/cardinality :db.cardinality/one}
; {:db/ident :foo/ref
;  :db/valueType :db.type/ref
;  :db/cardinality :db.cardinality/one}
; {:db/ident :myAdd
;  :db/fn #db/fn {:lang :clojure
;                 :params [db e a v]
;                 :code [[:db/add (:db/id (d/entity db e)) a v]]}}]

(def schema (read-string (slurp "/Users/jbin/Desktop/Jaret/Projects/workproof/merge/resources/stringschema.edn")))
@(d/transact conn schema)

;; The other examples are indirectly this.
@(d/transact conn
             [[:db/add "a" :foo/name "x"]
              [:db/add "b" :foo/name "y"]
              [:db/add "a" :foo/ref "b"]]))

;; Works! Note that d/entity resolves tempid.
(let [a (d/tempid :db.part/user)]
  @(d/transact conn
               [[:db/add a :foo/name "x"]
                [:db/add "b" :foo/name "y"]
                [:myAdd a :foo/ref "b"]]))

;; Fails with :db.error/not-a-keyword.
@(d/transact conn
             [[:db/add "a" :foo/name "x"]
              [:db/add "b" :foo/name "y"]
              [:myAdd "a" :foo/ref "b"]])