[bug#74151] [PATCH 3/7] system/vm: Fix virtual-machine bug.

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

The virtual-machine syntax would not accept a single operating-system field,
which was puzzling.

* gnu/system/vm.scm (virtual-machine): Add a pattern matching a single literal
'operating-system' field and value.

Change-Id: If207fd71df3a3f763b2e63229eafa82f63e80773
---
 gnu/system/vm.scm | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index a2743453e7..4a400056d7 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -422,10 +422,14 @@ (define-record-type* <virtual-machine> %virtual-machine
                     (default #f)))
 
 (define-syntax virtual-machine
-  (syntax-rules ()
+  (syntax-rules (operating-system)
     "Declare a virtual machine running the specified OS, with the given
 options."
-    ((_ os)                                       ;shortcut
+    ((_ (operating-system os))
+     ;; Also accept the long form (virtual-machine (operating-system os)), for
+     ;; correctness.
+     (%virtual-machine (operating-system os)))
+    ((_ os)                             ;shortcut
      (%virtual-machine (operating-system os)))
     ((_ fields ...)
      (%virtual-machine fields ...))))
-- 
2.46.0