Allow @ to work with (ice-9 syncase)

(Reported by Panicz Maciej Godek.)

* test-suite/tests/syncase.test ("@ works with syncase"): New test.

* ice-9/syncase.scm (guile-macro): When a Guile macro transformer
  produces a variable, don't pass it through sc-expand.

NEWS

@@ -50,6 +50,13 @@ Changes in 1.8.7 (since 1.8.6)
 ** Fix build problem when scm_t_timespec is different from struct timespec
 ** Fix build when compiled with -Wundef -Werror
 
+** Allow @ macro to work with (ice-9 syncase)
+
+Previously, use of the @ macro in a module whose code is being
+transformed by (ice-9 syncase) would cause an "Invalid syntax" error.
+Now it works as you would expect (giving the value of the specified
+module binding).
+
 
 Changes in 1.8.6 (since 1.8.5)
 

THANKS

@@ -41,6 +41,7 @@ For fixes or providing information which led to a fix:
           Peter Gavin
            Eric Gillespie, Jr
          Didier Godefroy
+  Panicz Maciej Godek
            John Goerzen
            Mike Gran
          Szavai Gyula

ice-9/syncase.scm

@@ -146,9 +146,11 @@
 		      (let ((e ((macro-transformer m)
 				e
 				(append r (list eval-closure)))))
+			(if (variable? e)
+			    e
 			    (if (null? r)
 				(sc-expand e)
-			    (sc-chi e r w))))))))))
+				(sc-chi e r w)))))))))))
 
 (define generated-symbols (make-weak-key-hash-table 1019))
 

test-suite/tests/syncase.test

@@ -34,3 +34,6 @@
 
 (pass-if "basic syncase macro"
   (= (plus 1 2 3) (+ 1 2 3)))
+
+(pass-if "@ works with syncase"
+  (eq? run-test (@ (test-suite lib) run-test)))