Index: src/tests/avltree/avl.h
===================================================================
--- src/tests/avltree/avl.h	(revision 14f6bb395794c1f66c011077161a28e327f18dd6)
+++ src/tests/avltree/avl.h	(revision 142cf5d5bc4083f9bfbdb71d2ae41cf1ec930d79)
@@ -61,5 +61,5 @@
 void ?{}(tree(K, V) *t, K key, V value);
 
-forall(otype K | Comparable(K), otype V)
+forall(otype K, otype V)
 void ^?{}(tree(K, V) * t);
 
Index: src/tests/avltree/avl1.c
===================================================================
--- src/tests/avltree/avl1.c	(revision 14f6bb395794c1f66c011077161a28e327f18dd6)
+++ src/tests/avltree/avl1.c	(revision 142cf5d5bc4083f9bfbdb71d2ae41cf1ec930d79)
@@ -12,5 +12,5 @@
 }
 
-forall(otype K | Comparable(K), otype V)
+forall(otype K, otype V)
 void ^?{}(tree(K, V) * t){
   delete(t->left);
Index: src/tests/avltree/avl_test.c
===================================================================
--- src/tests/avltree/avl_test.c	(revision 14f6bb395794c1f66c011077161a28e327f18dd6)
+++ src/tests/avltree/avl_test.c	(revision 142cf5d5bc4083f9bfbdb71d2ae41cf1ec930d79)
@@ -25,5 +25,5 @@
 
   // int -> char *
-  tree(int, char *) * smap = create(-1, "baz");
+  tree(int, const char *) * smap = create(-1, "baz");
   insert(&smap, 12, "bar");
   insert(&smap, 2, "foo");
@@ -35,17 +35,17 @@
   delete(smap);
 
-  // char* -> char*
-  struct c_str { char *str; };  // wraps a C string
-  int ?<?(c_str a, c_str b) {
-    return strcmp(a.str,b.str) < 0;
+  // const char* -> const char*
+  int ?<?(const char * a, const char * b) {
+    return strcmp(a, b) < 0;
   }
-  tree(c_str, char *) * ssmap = create((c_str){"queso"}, "cheese");
-  insert(&ssmap, (c_str){"foo"}, "bar");
-  insert(&ssmap, (c_str){"hello"}, "world");
+
+  tree(const char *, const char *) * ssmap = create("queso", "cheese");
+  insert(&ssmap, "foo", "bar");
+  insert(&ssmap, "hello", "world");
   assert( height(ssmap) == 2 );
 
-  printf("%s %s %s\n", *find(ssmap, (c_str){"hello"}), *find(ssmap, (c_str){"foo"}), *find(ssmap, (c_str){"queso"}));
+  printf("%s %s %s\n", *find(ssmap, "hello"), *find(ssmap, "foo"), *find(ssmap, "queso"));
 
-  remove(&ssmap, (c_str){"foo"});
+  remove(&ssmap, "foo");
   delete(ssmap);
 }