Brief

This patch block to compile these functions below:

(fn [a r g s]) (fn ([a r g s])) (defn name [a r g s]) (defn name ([a r g s]))

and force you to write a body or nil. (In the Clojure Compiler, they return nil.)

Reason

• (fn [arg]) which has no body is used to return nil at any time but there's (constantly nil) for it.
• On the other hand, it would be difficult (and I stucked in) to fix bugs about applying ~@ to '() in a defmacro clause with a careless oversight because this wouldn't spit an error in a couple of cases.

Example

with this:

user=> (defn foo [bar])
Syntax error (IllegalArgumentException) compiling at (REPL:1:1).
([bar]) has no body. fn/defn must have them.

user=> (defn foo [bar] (inc 1))
#'user/foo

without (it's normal):

user=> (defn foo [bar]) 
#'user/foo

with:

user=> `(fn [a] ~@(filter even? [1 3 5]))
(clojure.core/fn [user/a])

user=> (defmacro aa [x y z] `(fn [] ~@(filter even? [x y z])))
#'user/aa

user=> (aa 1 3 5)
Syntax error macroexpanding clojure.core/fn at (REPL:1:1).
(fn([])) has no body. fn/defn must have them.

user=> (aa 1 2 3)
#object[user$eval149$fn__150 0x32c8e539 "user$eval149$fn__150@32c8e539"]

without:

user=> `(fn [a] ~@(filter even? [1 3 5])) 
(clojure.core/fn [user/a])

user=> (defmacro aa [x y z] `(fn [] ~@(filter even? [x y z])))
#'user/aa

user=> (aa 1 3 5)
#object[user$eval148$fn__149 0x70efb718 "user$eval148$fn__149@70efb718"]

user=> (aa 1 2 3)
#object[user$eval152$fn__153 0x4e70a728 "user$eval152$fn__153@4e70a728"]

How to use

• Patching
  1. git clone https://github.com/taiyakihitotsu/ClojureFnPatch
  2. cd ./ClojureFnPatch
  3. git clone https://github.com/clojure/clojure.git
  4. patch -d clojure -p1 < defnfix-patch-proto.patch
• Tests
  1. cd ./clojure
  2. mvn clean test
• Repl
  1. mvn -Plocal -Dmaven.test.skip=true package
  2. java -jar clojure.jar

Confirmed Version

• 1.12.0-rc gentoo
• 1.12.0-master-SNAPSHOT
• 1.13.1 gentoo

Author

Taiyakihitotsu

License

EPL