[project @ 2003-07-23 13:08:22 by simonpj]

Comment case-alternative invariants

diff --git a/ghc/compiler/coreSyn/CoreSyn.lhs b/ghc/compiler/coreSyn/CoreSyn.lhs
index edee0dd..4c70bb3 100644 (file)
--- a/ghc/compiler/coreSyn/CoreSyn.lhs
+++ b/ghc/compiler/coreSyn/CoreSyn.lhs
@@ -79,7 +79,8 @@ data Expr b   -- "b" for the type of binders,
   | Lam   b (Expr b)
   | Let   (Bind b) (Expr b)
   | Case  (Expr b) b [Alt b]   -- Binder gets bound to value of scrutinee
-                               -- DEFAULT case must be *first*, if it occurs at all
+       -- Invariant: the list of alternatives is ALWAYS EXHAUSTIVE
+       -- Invariant: the DEFAULT case must be *first*, if it occurs at all
   | Note  Note (Expr b)
   | Type  Type                 -- This should only show up at the top
                                -- level of an Arg