Pseudo-variable "Message" not handled correctly in message types

[senier]

package Test is

   type Inner is
      message
         null
            then Data
               with Length => Message'Length;
         Data : Opaque;
      end message;

   type Outer is
      message
         A : Boolean;
         Inner : Inner;
         B : Boolean;
      end message;

end Test;

$ rflx check test.rflx
Parsing test.rflx
Processing Test
test.rflx:6:18: model: error: unreachable field "Inner_Data" in "Test::Outer"
test.rflx:6:18: model: info: path 0 (A -> Inner_Data):
test.rflx:6:18: model: info: unsatisfied "Inner_Data'Last = (A'Last + 1 + Message'Length) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Last >= Inner_Data'Last"
test.rflx:13:10: model: info: unsatisfied "A'Last = (Message'First + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Length = Message'Last - Message'First + 1"
test.rflx:15:10: model: error: unreachable field "B" in "Test::Outer"
test.rflx:15:10: model: info: path 0 (A -> Inner_Data -> B):
test.rflx:6:18: model: info: unsatisfied "Inner_Data'Last = (A'Last + 1 + Message'Length) - 1"
test.rflx:15:10: model: info: unsatisfied "B'Last = (Inner_Data'Last + 1 + 1) - 1"
test.rflx:13:10: model: info: unsatisfied "A'Last = (Message'First + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Last >= B'Last"
test.rflx:11:4: model: info: unsatisfied "Message'Length = Message'Last - Message'First + 1"
model: error: unreachable field "Final" in "Test::Outer"
model: info: path 0 (A -> Inner_Data -> B -> Final):
test.rflx:6:18: model: info: unsatisfied "Inner_Data'Last = (A'Last + 1 + Message'Length) - 1"
test.rflx:15:10: model: info: unsatisfied "B'Last = (Inner_Data'Last + 1 + 1) - 1"
test.rflx:13:10: model: info: unsatisfied "A'Last = (Message'First + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Last >= B'Last"
test.rflx:11:4: model: info: unsatisfied "Message'Length = Message'Last - Message'First + 1"
model: error: contradicting condition in "Test::Outer"
test.rflx:13:10: model: info: on path: "A"
test.rflx:6:18: model: info: on path: "Inner_Data"
test.rflx:13:10: model: info: unsatisfied "A'Last = (Message'First + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Length = Message'Last - Message'First + 1"
test.rflx:6:18: model: info: unsatisfied "Inner_Data'Last = (A'Last + 1 + Message'Length) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Last >= Inner_Data'Last"
model: error: contradicting condition in "Test::Outer"
test.rflx:13:10: model: info: on path: "A"
test.rflx:6:18: model: info: on path: "Inner_Data"
test.rflx:15:10: model: info: on path: "B"
test.rflx:13:10: model: info: unsatisfied "A'Last = (Message'First + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Length = Message'Last - Message'First + 1"
test.rflx:6:18: model: info: unsatisfied "Inner_Data'Last = (A'Last + 1 + Message'Length) - 1"
test.rflx:15:10: model: info: unsatisfied "B'Last = (Inner_Data'Last + 1 + 1) - 1"
test.rflx:11:4: model: info: unsatisfied "Message'Last >= B'Last"

[treiher]

The issue will be obsolete after realization of #736, as the use of Message'Size in size aspects will be prohibited. The use case can be realized by parameterized messages.