2008: Generic Package fails with signed type, but not integer

[bpadalino]

package testpkg is
  generic (
    type A ;
    val : A ;
    function to_string(x : A) return string is <> ;
  ) ;

    constant x : A := val ;

    function doit(l, r : A) return string ;

end package ;

package body testpkg is

    function doit(l, r : A) return string is
    begin
        return to_string(l) & to_string(r) ;
    end function ;

end package body ;

library ieee ;
    use ieee.std_logic_1164.all ;
    use ieee.numeric_std.all ;

entity test is
end entity ;

architecture arch of test is


    --package test_int is new work.testpkg generic map(A => integer, val => 12) ;
    package test_signed is new work.testpkg generic map (A => signed, val => to_signed(12, 16)) ;

begin

    tb : process
    begin
        --report test_int.doit(44, 55) ;
        report test_signed.doit(to_signed(44, 16), to_signed(55, 16)) ;
        std.env.stop ;
    end process ;

end architecture ;

The integer version works, but not the signed version.

$ nvc --std=2019 -a test.vhdl -e test -r
** Fatal: tree kind T_ALIAS does not have item I_PORTS
[0x5599b8e2a2f9] ../src/object.c:254 object_lookup_failed
[0x5599b8e27692] ../src/tree.c:595 tree_ports
[0x5599b8e27692] ../src/tree.c:50 simp_call_args.cold
[0x5599b8ea2f3d] ../src/simp.c:238 simp_fcall
[0x5599b8ea2f3d] ../src/simp.c:1565 simp_tree.lto_priv.0
[0x5599b8eb7b44] ../src/object.c:714 object_rewrite
[0x5599b8eb7ba6] ../src/object.c:778 object_rewrite
[0x5599b8eb7d74] ../src/object.c:789 object_rewrite
[0x5599b8eb7ba6] ../src/object.c:778 object_rewrite
[0x5599b8eb7d74] ../src/object.c:789 object_rewrite
[0x5599b8eb7d74] ../src/object.c:789 object_rewrite
[0x5599b8eb7d74] ../src/object.c:789 object_rewrite
[0x5599b8f79eaf] ../src/tree.c:1302 tree_rewrite.isra.0
[0x5599b8eb587c] ../src/simp.c:1700 analyse_file
[0x5599b8e3a60a] ../src/nvc.c:246 analyse
[0x5599b8e3a60a] ../src/nvc.c:1920 process_command
[0x5599b8e314e5] ../src/nvc.c:2060 main

[nickg]

The difference is to_signed is an alias for signed but an implicit subprogram for integer.