Invalid dependency resolution

[senier]

Dependencies are not resolved correctly in some cases. This is true for the current parser as well as the new parser developed in #547:

package P1 is
   type Kind is mod 2**16;
   type Frame is
      message
         Kind : Kind;
         Payload : Opaque
            with Size => Message'Last - Kind'Last;
      end message;
end P1;

package P4 is
   type Protocol_Number is mod 2**16;
end P4;

with P4;
package P2 is
   type Length is mod 2**16;
   type Packet is
      message
         Length : Length;
         Protocol : P4::Protocol_Number;
         Payload : Opaque
            with Size => 8 * Length;
      end message;
end P2;

with P2;
package P3 is
   type T is mod 2**32;
   type Packet is
      message
         F1 : T;
         F2 : P2::Length;
      end message;
end P3;

with P1;
with P2;
with P3;
package In_P1 is
   for P1::Frame use (Payload => P2::Packet)
      if Kind = 1;
   for P1::Frame use (Payload => P3::Packet)
      if Kind = 2;
end In_P1;

When checking In_P1, the new parser yields:

Processing P2
Processing P3
Processing P4
Processing P1
Processing In_P1
p2.rflx:10:10: model: error: missing type for field "Protocol" in "P2::Packet"
in_p1.rflx:7:34: parser: error: undefined type "P2::Packet" in refinement of "P1::Frame"

As can be seen, the dependency resolution yields P2, P3, P4, P1, In_P4, whereas the correct order would be P4, P1, P2, P3, In_P1 or P1, P4, P2, P3, In_P1 (i.e. post-order DFS).

The current parser has the same issue (but different subsequent errors):

Processing P2
Processing P3
Processing P4
Processing P1
Processing In_P1
in_p1.rflx:1:6: parser: error: dependency cycle when including "P1"
in_p1.rflx:2:6: parser: info: when including "P2"
p2.rflx:1:6: parser: info: when including "P4"
in_p1.rflx:3:6: parser: info: when including "P3"
p3.rflx:1:6: parser: info: when including "P2"
p2.rflx:10:10: model: error: missing type for field "Protocol" in "P2::Packet"
in_p1.rflx:7:34: parser: error: undefined type "P2::Packet" in refinement of "P1::Frame"