import/cran: Detect library references in "check_installed".

* guix/import/cran.scm (import-pattern): Add case for "check_installed".
* tests/import/cran.scm: Add test.

Change-Id: Id69371158eecaeb371056e6954a3109687346c22

guix/import/cran.scm

@@ -570,7 +570,7 @@ referenced in build system files."
     ;; Quiet imports
     "(suppressPackageStartupMessages\\()?"
     ;; the actual import statement.
-    "(require|library)\\(\"?([^, \")]+)"
+    "(require|library|check_installed)\\(\"?([^, \")]+)"
     ;; Or perhaps...
     "|"
     ;; ...direct namespace access.

tests/import/cran.scm

@@ -103,6 +103,11 @@ Date/Publication: 2015-07-14 14:15:16
   (set->list ((@ (guix import cran) extract-imports)
               "this:is:not::a:procedure")))
 
+(test-equal "extract-imports: matches things before a comma"
+  (list "MASS")
+  (set->list ((@ (guix import cran) extract-imports)
+              "check_installed(\"MASS\",")))
+
 (test-equal "r-minimal is not a cran package"
   #f
   ((@@ (guix import cran) cran-package?) r-minimal))