Adjust new [assert] to work properly from top.ur

2 files changed, 9 insertions, 2 deletions

diff --git a/lib/ur/top.ur b/lib/ur/top.ur
index 06dcab5f..e831b4f7 100644
--- a/lib/ur/top.ur
+++ b/lib/ur/top.ur
@@ -412,4 +412,4 @@ fun min [t] ( _ : ord t) (x : t) (y : t) : t =
     if x < y then x else y
 
 fun assert [a] (cond: bool) (msg: string) (loc: string) (x:a): a =
-  if cond then x else error <xml>{[msg]} at {[loc]}</xml>
+  if cond then x else error <xml>{txt msg} at {txt loc}</xml>
diff --git a/lib/ur/top.urs b/lib/ur/top.urs
index 15bc6a22..907b28b2 100644
--- a/lib/ur/top.urs
+++ b/lib/ur/top.urs
@@ -35,7 +35,7 @@ con snd3 = K1 ==> K2 ==> K3 ==> fn t :: (K1 * K2 * K3) => t.2
 con thd3 = K1 ==> K2 ==> K3 ==> fn t :: (K1 * K2 * K3) => t.3
 
 (* Convert a record of n Units into a type-level record where
-   each field has the same value (which describes a uniformly
+o   each field has the same value (which describes a uniformly
    typed record) *)
 con mapU = K ==> fn f :: K => map (fn _ :: Unit => f)
 
@@ -290,3 +290,10 @@ val postFields : postBody -> list (string * string)
 
 val max : t ::: Type -> ord t -> t -> t -> t
 val min : t ::: Type -> ord t -> t -> t -> t
+
+val assert : t ::: Type
+             -> bool   (* Did we avoid something bad? *)
+             -> string (* Explanation of the bad thing *)
+             -> string (* Source location of the bad thing *)
+             -> t      (* Return this value if all went well. *)
+             -> t