1 files changed, 45 insertions, 0 deletions
diff --git a/stdlib/source/library/lux/meta/type/variance.lux b/stdlib/source/library/lux/meta/type/variance.lux
new file mode 100644
index 000000000..ac7e120d4
--- /dev/null
+++ b/stdlib/source/library/lux/meta/type/variance.lux
@@ -0,0 +1,45 @@
+(.require
+ [library
+  [lux (.except)
+   [meta
+    ["[0]" symbol]]]])
+
+(type .public (Co it)
+  (-> Any it))
+
+(type .public (Contra it)
+  (-> it Any))
+
+(type .public (In it)
+  (-> it it))
+
+(type .public (Mutable r w)
+  (Primitive "#Mutable" [(-> w r)]))
+
+(with_template [<name> <type>]
+  [(def .public <name>
+     (template (<name> it)
+       [((.is (.All (_ r w) <type>)
+              (.|>> .as_expected))
+         it)]))]
+
+  [read (.-> (..Mutable r w) r)]
+  [write (.-> w (..Mutable r w))]
+  )
+
+(type .public (Read_Only a)
+  (Mutable a Nothing))
+
+(type .public (Write_Only a)
+  (Mutable Any a))
+
+(with_template [<name> <type>]
+  [(def .public <name>
+     (template (<name> it)
+       [((.is (.All (_ r w) <type>)
+              (.|>>))
+         it)]))]
+
+  [read_only (.-> (..Mutable r w) (..Read_Only r))]
+  [write_only (.-> (..Mutable r w) (..Write_Only w))]
+  )