Add a test case for previous commit

Also make unifying int against int('n) work as expected for
constructor applications.

2 files changed, 31 insertions, 0 deletions

diff --git a/src/type_check.ml b/src/type_check.ml
index 1afd9765..de1c1ae1 100644
--- a/src/type_check.ml
+++ b/src/type_check.ml
@@ -1585,6 +1585,9 @@ let rec unify_typ l env goals (Typ_aux (aux1, _) as typ1) (Typ_aux (aux2, _) as
 
   | Typ_var v, _ when KidSet.mem v goals -> KBindings.singleton v (arg_typ typ2)
 
+  (* We need special cases for unifying range(n, m), nat, and int vs atom('n) *)
+  | Typ_id int, Typ_app (atom, [A_aux (A_nexp n, _)]) when string_of_id int = "int" -> KBindings.empty
+
   | Typ_id nat, Typ_app (atom, [A_aux (A_nexp n, _)]) when string_of_id nat = "nat" ->
      if prove __POS__ env (nc_gteq n (nint 0)) then KBindings.empty
      else unify_error l (string_of_typ typ2 ^ " must be a natural number")
diff --git a/test/typecheck/pass/existential_ast2.sail b/test/typecheck/pass/existential_ast2.sail
new file mode 100644
index 00000000..f15d1f57
--- /dev/null
+++ b/test/typecheck/pass/existential_ast2.sail
@@ -0,0 +1,28 @@
+default Order dec
+
+$include <prelude.sail>
+
+type datasize('n: Int) -> Bool = 'n in {32, 64}
+
+type regno = range(0, 31)
+
+union ast = {
+  Ctor1 : {'d, datasize('d). (nat, int('d), bits(4))},
+  Ctor2 : {'d, datasize('d). (int, int('d), bits(4))},
+}
+
+val decode : bits(16) -> option(ast)
+
+function clause decode(a : bits(4) @ b : bits(1) @ c : bits(4) @ 0b0000110) = {
+  let x : {|32, 64|} = if b == 0b0 then 32 else 64;
+  let a = unsigned(a);
+
+  Some(Ctor1(a, x, c))
+}
+
+function clause decode(a : bits(4) @ b : bits(1) @ c : bits(4) @ 0b0000111) = {
+  let x : {|32, 64|} = if b == 0b0 then 32 else 64;
+  let a = unsigned(a);
+
+  Some(Ctor2(a, x, c))
+}