check io.open return

main.fnl

@@ -8,6 +8,12 @@
 (local pkey (require :openssl.pkey))
 (local bignum (require :openssl.bignum))
 
+;; ncall is the opposite of pcall: "non-protected call"
+(macro ncall [f]
+  `(case ,f
+     ok# ok#
+     (nil err#) (error err#)))
+
 (fn string->bignum [bytes]
   (bignum.new
    (string.format
@@ -34,10 +40,10 @@
   (out:write_chunk text true))
 
 (fn slurp [filename]
-  (with-open [f (io.open filename "r")] (f:read "*a")))
+  (with-open [f (ncall (io.open filename "r"))] (f:read "*a")))
 
 (fn read-line [filename]
-  (with-open [f (io.open filename "r")] (f:read "l")))
+  (with-open [f (ncall (io.open filename "r"))] (f:read "l")))
 
 (fn assoc [tbl k v & more]
   (tset tbl k v)
@@ -106,12 +112,6 @@
       _
       (send-error out 404 "not found"))))
 
-;; ncall is the opposite of pcall: "non-protected call"
-(macro ncall [f]
-  `(case ,f
-     ok# ok#
-     (nil err#) (error err#)))
-
 (fn new-server []
   (let [(addr port) (string.match options.bind-address "(.+):(%d+)$")]
     (case (server.listen