core.typed and core.match failing to get along, with multimethods this time

lambda.clj

(ns type-test.lambda
  (require [clojure.core.typed :refer :all]
           [clojure.core.match :refer [match]]))

(def-alias Expr "An expression"
  (Rec [e]
       (U '[(Value :var) Symbol]
          '[(Value :lam) Symbol e]
          '[(Value :app) e e])))

(ann free? (Fn [Expr Symbol -> Boolean]))
(defmulti free? (fn [expr var] (first expr)))
(defmethod free? :var [[_ sym] var] (= sym var))
(defmethod free? :lam [[_ arg body] var] (and (not= arg var) (free? body var)))
(defmethod free? :app [[_ func expr] var] (or (free? func var) (free? expr var)))

output

Initializing core.typed ...
Building core.typed base environments ...
Finished building base environments
"Elapsed time: 4289.650169 msecs"
core.typed initialized.
Start collecting type-test.lambda
Finished collecting type-test.lambda
Collected 1 namespaces in 5638.999324 msecs
Start checking type-test.lambda
Checked type-test.lambda in 421.090446 msecs
Checked 1 namespaces (approx. 15 lines) in 6064.178849 msecs
Type Error (type_test/lambda.clj:14:62) Type mismatch:

Expected: 	Expr

Actual: 	(U nil type-test.lambda/Expr)
in: (free? body var)


Type Error (type_test/lambda.clj:15:47) Type mismatch:

Expected: 	Expr

Actual: 	(U Symbol type-test.lambda/Expr)
in: (free? func var)


Type Error (type_test/lambda.clj:15:64) Type mismatch:

Expected: 	Expr

Actual: 	(U nil type-test.lambda/Expr)
in: (free? expr var)


Type Checker: Found 3 errors
Found errors
Subprocess failed