Mercurial > urweb
changeset 238:44a1663ad893
Checking for well-formed 'val rec'
| author | Adam Chlipala <adamc@hcoop.net> |
|---|---|
| date | Thu, 28 Aug 2008 13:13:16 -0400 |
| parents | 9182068c9d7c |
| children | fc6f04889bf2 |
| files | src/elaborate.sml tests/recBad.lac |
| diffstat | 2 files changed, 25 insertions(+), 0 deletions(-) [+] |
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--- a/src/elaborate.sml Thu Aug 28 12:58:11 2008 -0400 +++ b/src/elaborate.sml Thu Aug 28 13:13:16 2008 -0400 @@ -1033,6 +1033,7 @@ | DuplicatePatField of ErrorMsg.span * string | Unresolvable of ErrorMsg.span * L'.con | OutOfContext of ErrorMsg.span * (L'.exp * L'.con) option + | IllegalRec of string * L'.exp fun expError env err = case err of @@ -1082,6 +1083,10 @@ | Unresolvable (loc, c) => (ErrorMsg.errorAt loc "Can't resolve type class instance"; eprefaces' [("Class constraint", p_con env c)]) + | IllegalRec (x, e) => + (ErrorMsg.errorAt (#2 e) "Illegal 'val rec' righthand side (must be a function abstraction)"; + eprefaces' [("Variable", PD.string x), + ("Expression", p_exp env e)]) fun checkCon (env, denv) e c1 c2 = unifyCons (env, denv) c1 c2 @@ -2826,6 +2831,13 @@ end | L.DValRec vis => let + fun allowable (e, _) = + case e of + L.EAbs _ => true + | L.ECAbs (_, _, _, e) => allowable e + | L.EDisjoint (_, _, e) => allowable e + | _ => false + val (vis, gs) = ListUtil.foldlMap (fn ((x, co, e), gs) => let @@ -2849,6 +2861,10 @@ val gs2 = checkCon (env, denv) e' et c' in + if allowable e then + () + else + expError env (IllegalRec (x, e')); ((x, n, c', e'), gs1 @ enD gs2 @ gs) end) gs vis in
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/tests/recBad.lac Thu Aug 28 13:13:16 2008 -0400 @@ -0,0 +1,9 @@ +datatype list a = Nil | Cons of a * list a + +val rec append : t ::: Type -> list t -> list t -> list t = fn t ::: Type => fn ls1 => fn ls2 => + case ls1 of + Nil => ls2 + | Cons (h, t) => Cons (h, append t ls2) + +(*val rec ones : list int = Cons (1, ones)*) +val rec ones : unit -> list int = fn () => Cons (1, ones ())