1 files changed, 13 insertions, 8 deletions
diff --git a/elab.sml b/elab.sml
index 032d1d7..52d0089 100644
--- a/elab.sml
+++ b/elab.sml
@@ -27,21 +27,26 @@ struct
     | Syntax.ETyped (e, _) => elab env e
     | Syntax.EAndAlso (_, _) => raise Fail "unimplemented"
     | Syntax.EOrElse (_, _) => raise Fail "unimplemented"
-    | Syntax.ELet (decls, body) =>
-        foldr
-          (fn (Syntax.DVal v, acc) =>
-            Syntax.LApp (Syntax.LFn (Gensym.new (), acc), elab env v))
-          (elab env body)
-          decls
-    | Syntax.ELambda (var, body) =>
+    | Syntax.ELet ([], body) => elab env body
+    | Syntax.ELet (Syntax.DVal (pat, v) :: decls, body) =>
+        elab env (Syntax.ECase (v, [(pat, Syntax.ELet (decls, body))]))
+    | Syntax.ELambda (pat, body) =>
         let
           val v = Gensym.new ()
           val env' =
-            case var of
+            case pat of
               Syntax.PWild => env
             | Syntax.PVar name => StringMap.insert name v env
         in Syntax.LFn (v, elab env' body)
         end
+    | Syntax.ECase (expr, []) => raise Fail "nonexhaustive match"
+    | Syntax.ECase (expr, (pat, body) :: rest) =>
+        if rest <> [] then raise Fail "redundant match" else
+        let val v = Gensym.new () in
+          case pat of
+            Syntax.PWild => Syntax.LApp (Syntax.LFn (v, elab env body), elab env expr)
+          | Syntax.PVar name => Syntax.LApp (Syntax.LFn (v, elab (StringMap.insert name v env) body), elab env expr)
+        end
 
   fun elaborate (p : Syntax.expr) : Syntax.lexp = elab StringMap.empty p
 end