packages: Use '@' in package record printers.

* guix/packages.scm <package>: Use '@' in record printer.
* guix/import/cabal.scm <cabal-package>: Likewise
* guix/import/elpa.scm <elpa-package>: Likewise.
* tests/packages.scm: Adapt to it.

guix/import/cabal.scm

@@ -608,7 +608,7 @@ (define-record-type <cabal-package>
 
 (set-record-type-printer! <cabal-package>
                           (lambda (package port)
-                            (format port "#<cabal-package ~a-~a>"
+                            (format port "#<cabal-package ~a@~a>"
                                       (cabal-package-name package)
                                       (cabal-package-version package))))
 

guix/import/elpa.scm

@@ -121,7 +121,7 @@ (define-record-type <elpa-package>
 
 (set-record-type-printer! <elpa-package>
                           (lambda (package port)
-                            (format port "#<elpa-package ~a-~a>"
+                            (format port "#<elpa-package ~a@~a>"
                                       (elpa-package-name package)
                                       (elpa-package-version package))))
 

guix/packages.scm

@@ -278,7 +278,7 @@ (define-record-type* <package>
                           (lambda (package port)
                             (let ((loc    (package-location package))
                                   (format simple-format))
-                              (format port "#<package ~a-~a ~a~a>"
+                              (format port "#<package ~a@~a ~a~a>"
                                       (package-name package)
                                       (package-version package)
                                       (if loc

tests/packages.scm

@@ -58,7 +58,7 @@ (define %store
 (test-begin "packages")
 
 (test-assert "printer with location"
-  (string-match "^#<package foo-0 foo.scm:42 [[:xdigit:]]+>$"
+  (string-match "^#<package foo@0 foo.scm:42 [[:xdigit:]]+>$"
                 (with-output-to-string
                   (lambda ()
                     (write
@@ -66,7 +66,7 @@ (define %store
                        (location (make-location "foo.scm" 42 7))))))))
 
 (test-assert "printer without location"
-  (string-match "^#<package foo-0 [[:xdigit:]]+>$"
+  (string-match "^#<package foo@0 [[:xdigit:]]+>$"
                 (with-output-to-string
                   (lambda ()
                     (write