flambda-backend: Prevent fatal errors related to regions (#2096)

Author: Ekdohibs

testsuite/tests/typing-local/local_gadt.ml

@@ -0,0 +1,14 @@
+(* TEST *)
+
+type (_, _) eq = Eq : ('a, 'a) eq
+
+let[@inline always] cast (type a b) (x : a) (Eq : (a, b) eq) : b = x
+
+let test (f : local_ 'a -> local_ 'b) (eq : (local_ 'a -> local_ 'b, 'a -> 'b) eq) (x : 'a) : 'b =
+  (cast f eq) x 
+
+type 'a box = Box of 'a
+
+let localf : (local_ 'a -> local_ 'a box) = fun x -> exclave_ (local_ (Box x))
+
+let g eq x = test localf eq x

testsuite/tests/typing-local/local_gadt.reference

@@ -0,0 +1,12 @@
+(* TEST *)
+
+type 'a box = Box of 'a
+module X : sig
+  val f : int -> string -> local_ int box
+end = struct
+  let[@inline never] f x y = exclave_ (local_ (Box x))
+end
+
+let[@inline always] h x = x
+
+let g a = (h X.f) a

testsuite/tests/typing-local/partial_app_bug.ml

@@ -0,0 +1,20 @@
+(* TEST *)
+
+type 'a box = Box of 'a
+
+let[@inline never] f x y z =
+  match x, y, z with Box x, Box y, Box z -> x + y + z
+
+type t = int box -> int box -> int
+let[@inline always] h x = x
+let g = (h f :> int box -> local_ t)
+
+let[@inline never] go a b c =
+  let local_ g1 = (g a) in
+  let g2 = (g1 b) in
+  g2 c
+
+let[@inline never] test () =
+  Format.eprintf "%d@." (go (Box 1) (Box 2) (Box 3))
+
+let () = test ()

testsuite/tests/typing-local/partial_app_bug.reference

@@ -0,0 +1 @@
+6