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GaloisInc · Sep 3, 2024 · ffe79ce · ffe79ce
1 parent 2103ce3
commit ffe79ce
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/src/Cryptol/TypeCheck/SimpType.hs b/src/Cryptol/TypeCheck/SimpType.hs
@@ -113,7 +113,13 @@ tSub :: Type -> Type -> Type
 tSub x y
   | Just t <- tOp TCSub (op2 nSub) [x,y] = t
   | tIsInf y  = tError (tf2 TCSub x y)
+
   | tIsInf x = x
+    {- This assumes that `y` is finite and not error.  The first should
+       follow from the typing on `tSub`, which asserts that the second argumet
+       is finite and less than the first;  the second should have been handleed
+       by the first equation above `tOp`. -}
+
   | Just 0 <- yNum = x
   | Just k <- yNum
   , TCon (TF TCAdd) [a,b] <- tNoUser x