generic types can be used like type classes. distinct can be applied to type classes.

tests/compile/ttypeclasses.nim

@@ -0,0 +1,34 @@
+type
+  TFoo[T] = object
+    val: T
+
+  T1 = distinct expr
+  T2 = distinct expr
+
+proc takesExpr(x, y) =
+  echo x, y
+
+proc same(x, y: T1) =
+  echo x, y
+
+proc takesFoo(x, y: TFoo) =
+  echo x.val, y.val
+
+proc takes2Types(x,y: T1, z: T2) =
+  echo x, y, z
+
+takesExpr(1, 2)
+takesExpr(1, "xxx")
+takesExpr[bool, int](true, 0)
+
+same(1, 2)
+same("test", "test")
+
+var f: TFoo[int]
+f.val = 10
+
+takesFoo(f, f)
+
+takes2Types(1, 1, "string")
+takes2Types[string, int]("test", "test", 1)
+