diff options
| -rw-r--r-- | compiler/typecheck/TcHsType.hs | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/compiler/typecheck/TcHsType.hs b/compiler/typecheck/TcHsType.hs index f931073ae1..37a867590a 100644 --- a/compiler/typecheck/TcHsType.hs +++ b/compiler/typecheck/TcHsType.hs @@ -938,8 +938,11 @@ tcTyVar mode name -- Could be a tyvar, a tycon, or a datacon | otherwise = do { (tc_ty, kind) <- instantiateTyN 0 ty tc_kind - ; traceTc "tcTyVar2b" (vcat [ ppr tc <+> dcolon <+> ppr tc_kind - , ppr tc_ty $$ ppr kind ]) + -- tc and tc_ty must not be traced here, because that would + -- force the evaluation of a potentially knot-tied variable (tc), + -- and the typechecker would hang, as per #11708 + ; traceTc "tcTyVar2b" (vcat [ ppr tc_tc <+> dcolon <+> ppr tc_kind + , ppr kind ]) ; return (tc_ty, kind) } where ty = mkNakedTyConApp tc [] |