06/10: Revert "packages: Optimize 'package-transitive-supported-systems'."

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit 86eee976f5ef21fa132de9827ad09a026bfdfd63
Author: Ludovic Courtès <address@hidden>
Date:   Tue Jul 3 13:49:28 2018 +0200

    Revert "packages: Optimize 'package-transitive-supported-systems'."
    
    This reverts commit 24420f5ffabfbdbe913a5765e5c00e17de18fb4c.
    
    This broke 'package-transitive-supported-systems', which would return
    the union of supported systems instead of the intersection.
---
 guix/packages.scm | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/guix/packages.scm b/guix/packages.scm
index cd7d3b8..c762fa7 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -766,16 +766,15 @@ in INPUTS and their transitive propagated inputs."
   (mlambdaq (package)
     "Return the intersection of the systems supported by PACKAGE and those
 supported by its dependencies."
-    (set->list
-     (fold (lambda (input systems)
-             (match input
-               ((label (? package? p) . _)
-                (fold set-insert systems
-                      (package-transitive-supported-systems p)))
-               (_
-                systems)))
-           (list->set (package-supported-systems package))
-           (bag-direct-inputs (package->bag package))))))
+    (fold (lambda (input systems)
+            (match input
+              ((label (? package? p) . _)
+               (lset-intersection
+                string=? systems (package-transitive-supported-systems p)))
+              (_
+               systems)))
+          (package-supported-systems package)
+          (bag-direct-inputs (package->bag package)))))
 
 (define* (supported-package? package #:optional (system (%current-system)))
   "Return true if PACKAGE is supported on SYSTEM--i.e., if PACKAGE and all its