lib/meta.nix: platformMatch: allow predicate functions

lib/meta.nix

@@ -78,10 +78,15 @@ rec {
 
        2. (modern) a pattern for the platform `parsed` field.
 
+       3. (functional) a predicate function returning a boolean.
+
      We can inject these into a pattern for the whole of a structured platform,
      and then match that.
   */
-  platformMatch = platform: elem: let
+  platformMatch = platform: elem:
+    if builtins.isFunction elem
+    then elem platform
+    else let
       pattern =
         if builtins.isString elem
         then { system = elem; }

pkgs/stdenv/generic/check-meta.nix

@@ -271,7 +271,7 @@ let
     sourceProvenance = listOf lib.types.attrs;
     maintainers = listOf (attrsOf anything); # TODO use the maintainer type from lib/tests/maintainer-module.nix
     priority = int;
-    platforms = listOf (either str (attrsOf anything));   # see lib.meta.platformMatch
+    platforms = listOf (oneOf [ str (attrsOf anything) (functionTo bool) ]);   # see lib.meta.platformMatch
     hydraPlatforms = listOf str;
     broken = bool;
     unfree = bool;