monads: Fix 'liftN' fallback case.

Reported by Andy Wingo <wingo@igalia.com>.

* guix/monads.scm (define-lift) <fallback case>: Add missing #'.  Remove
  extra formal parameter.
* tests/monads.scm ("lift"): Add test with 'lift1' as a procedure.

1 files changed, 4 insertions, 4 deletions

diff --git a/guix/monads.scm b/guix/monads.scm
index 61cd533bf4..0b0ad239de 100644
--- a/guix/monads.scm
+++ b/guix/monads.scm
@@ -239,10 +239,10 @@ CONDITION is true, return *unspecified* in the current monad."
             (identifier? #'id)
             ;; Slow path: Return a closure-returning procedure (we don't
             ;; guarantee (eq? LIFTN LIFTN), but that's fine.)
-            (lambda (liftn proc monad)
-              (lambda (args ...)
-                (with-monad monad
-                  (return (proc args ...))))))))))))
+            #'(lambda (proc monad)
+                (lambda (args ...)
+                  (with-monad monad
+                    (return (proc args ...))))))))))))
 
 (define-lift lift0 ())
 (define-lift lift1 (a))