exprIsHNF should "look through" lets

I can't quite remember when I spotted this, but exprIsHNF (and
similarly exprIsConLike) should ignore enclosing let-bindings,
since they don't affect termination.

diff --git a/compiler/coreSyn/CoreUtils.lhs b/compiler/coreSyn/CoreUtils.lhs
index 58beaf0..d200f81 100644 (file)
--- a/compiler/coreSyn/CoreUtils.lhs
+++ b/compiler/coreSyn/CoreUtils.lhs
@@ -736,6 +736,7 @@ exprIsHNFlike is_con is_con_unf = is_hnf_like
     is_hnf_like (Cast e _)       = is_hnf_like e
     is_hnf_like (App e (Type _)) = is_hnf_like e
     is_hnf_like (App e a)        = app_is_value e [a]
+    is_hnf_like (Let _ e)        = is_hnf_like e  -- Lazy let(rec)s don't affect us
     is_hnf_like _                = False
 
     -- There is at least one value argument