Variant on Tree, try not to expand too much

tests/aside/Test1.newt

@@ -0,0 +1,11 @@
+module Test1
+
+-- This is not total
+nat : U
+nat = {C : U} -> C -> (nat -> C) -> C
+
+-- TESTCASE This was broken when I wasn't expanding Ref ty in check
+-- Also broken when I tried to put Def in VRef
+-- Broken if I don't `nf` the type of a function before putting in TopContext
+succ : nat -> nat
+succ = \n => \ z s => s n