CLJ-1868 Avoid compiler NPE when checking class return type

Signed-off-by: Stuart Halloway <stu@cognitect.com>

Author: puredanger

src/clj/clojure/core.clj

@@ -244,9 +244,10 @@
                           (if (instance? clojure.lang.Symbol tag)
                             (if (clojure.lang.Util/equiv (.indexOf (.getName tag) ".") -1)
                               (if (clojure.lang.Util/equals nil (clojure.lang.Compiler$HostExpr/maybeSpecialTag tag))
-                                (let [t (.getName (clojure.lang.Compiler$HostExpr/maybeClass tag false))
-                                      resolvedtag (clojure.lang.Symbol/intern t)]
-                                  (with-meta argvec (assoc m :tag resolvedtag)))
+                                (let [c (clojure.lang.Compiler$HostExpr/maybeClass tag false)]
+                                  (if c
+                                    (with-meta argvec (assoc m :tag (clojure.lang.Symbol/intern (.getName c))))
+                                    argvec))
                                 argvec)
                               argvec)
                             argvec)))]

test/clojure/test_clojure/compilation.clj

@@ -145,6 +145,12 @@
     (is (= 'java.lang.String (-> arglists first meta :tag)))
     (is (= 'java.lang.Integer (-> arglists second meta :tag)))))
 
+(deftest CLJ-1232-return-type-not-imported
+  (is (thrown-with-msg? Compiler$CompilerException #"Unable to resolve classname: Closeable"
+                        (eval '(defn a ^Closeable []))))
+  (is (thrown-with-msg? Compiler$CompilerException #"Unable to resolve classname: Closeable"
+                        (eval '(defn a (^Closeable []))))))
+
 (defn ^String hinting-conflict ^Integer [])
 
 (deftest calls-use-arg-vector-hint