Problem with type aliases in SMT backend using version 0.15

[rmn30]

default Order dec

$include <arith.sail>
$include <vector_dec.sail>

type r1 = range(0, ((2 ^ 32) - 1))

function foo (x : bits(32)) -> r1 = {
    unsigned(x)
}

$property
function prop (x : bits(32)) -> bool = {
    foo(x) == 0
}

Compiling the above file with sail -smt produces an error:

Type error:
test.sail:8.13-33:
8 |function foo (x : bits(32)) -> r1 = {
  |             ^------------------^
  | . range(0, (2 ^ 32 - 1)) and . r1 do not match between function and val spec

If you substitute the type alias manually the error goes away.

[rmn30]

I should also note that the error is new in version 0.15 and that it does not occur with the C backend.

[rmn30]

Thanks!