Issue 907: Case expressions

[senier]

Part of #907

[jklmnn]

I cannot assign values to a variable with a case expression, as in this example:

with Universal;

package Test is

   type T is range 0 .. 256 with Size => 16;

   generic
      Channel : Channel with Readable, Writable; -- §S-P-C-RW
   session Session with
      Initial => Start,
      Final => Terminated
   is
      Message : Universal::Message; -- §S-D-V-T-M, §S-D-V-E-N
      Test_Var : T;
   begin
      state Start is
      begin
         Channel'Read (Message); -- §S-S-A-RD-V
      transition
         goto Prepare
            if Message'Valid -- §S-S-T-VAT, §S-E-AT-V-V
         goto Terminated -- §S-S-T-N
      end Start;

      state Prepare is
         Recv_Type : Universal::Message_Type; -- §S-D-V-T-SC
      begin
         Recv_Type := Message.Message_Type; -- §S-S-A-A-V
         -- §S-S-A-A-MA
         Message := Universal::Message'(Message_Type => Universal::MT_Value,
                                        Length       => 1,
                                        Value        => -- §S-E-CE
                                                        (case Recv_Type is
                                                         when Universal::MT_Null | Universal::MT_Data =>   2,
                                                         when Universal::MT_Value                     =>   8,
                                                         when Universal::MT_Values                    =>  16,
                                                         when Universal::MT_Option_Types              =>  32,
                                                         when Universal::MT_Options                   =>  64,
                                                         when Universal::MT_Unconstrained_Data        => 128,
                                                         when Universal::MT_Unconstrained_Options     => 256));
         Test_Var := (case Recv_Type is
                      when Universal::MT_Null | Universal::MT_Data =>   2,
                      when Universal::MT_Value                     =>   8,
                      when Universal::MT_Values                    =>  16,
                      when Universal::MT_Option_Types              =>  32,
                      when Universal::MT_Options                   =>  64,
                      when Universal::MT_Unconstrained_Data        => 128,
                      when Universal::MT_Unconstrained_Options     => 256);
      transition
         goto Reply -- §S-S-T-N
      exception
         goto Terminated -- §S-S-E
      end Prepare;

      state Reply is
      begin
         Channel'Write (Message); -- §S-S-A-WR-V
      transition
         goto Terminated -- §S-S-T-N
      end Reply;

      state Terminated is null state; -- §S-S-N
   end Session;

end Test;

I get the following error:

------------------------------ RecordFlux Bug ------------------------------
RecordFlux 0.6.0-pre   
RecordFlux-parser 0.11.0
attrs 21.2.0             
icontract 2.6.0
pydantic 1.9.0                                               
pydotplus 2.0.2    
ruamel.yaml 0.17.20
z3-solver 4.8.14.0  
                                                                      
Optimized: True                                
                                                                      
Command: /.../rflx generate test.rflx -d out
                                                                      
Traceback (most recent call last):  
  File "/.../RecordFlux/rflx/cli.py", line 202, in main
    args.func(args)
  File "/.../RecordFlux/rflx/cli.py", line 260, in generate
    Generator(                                              
  File "/.../RecordFlux/rflx/generator/generator.py", line 143, in generate
    units = self._generate(model, integration)           
  File "/.../RecordFlux/rflx/generator/generator.py", line 266, in _generate
    units.update(self._create_session(s, integration))                                                                                      
  File "/.../RecordFlux/rflx/generator/generator.py", line 283, in _create_session
    session_generator = SessionGenerator(                         
  File "/.../RecordFlux/rflx/generator/session.py", line 221, in __init__
    self._create()                                                                                                                          
  File "/.../RecordFlux/rflx/generator/session.py", line 251, in _create    
    state_machine = self._create_state_machine()                                                                                            
  File "/.../RecordFlux/rflx/generator/session.py", line 370, in _create_state_machine
    unit += self._create_states(self._session, composite_globals, is_global)                                 
  File "/.../RecordFlux/rflx/generator/session.py", line 861, in _create_states
    *[                                                                                                                                      
  File "/.../RecordFlux/rflx/generator/session.py", line 864, in <listcomp>
    for s in self._state_action(                                                                                                            
  File "/.../RecordFlux/rflx/generator/session.py", line 1950, in _state_action
    result = self._assign(                                                                                                                  
  File "/.../RecordFlux/rflx/generator/session.py", line 2270, in _assign
    _unexpected_expression(expression, "in assignment")                                                                                     
  File "/.../RecordFlux/rflx/generator/session.py", line 4757, in _unexpected_expression
    fatal_fail(                                                                                                                             
  File "/.../RecordFlux/rflx/error.py", line 198, in fatal_fail
    _fail(FatalError(), message, subsystem, severity, location)
  File "/.../RecordFlux/rflx/error.py", line 209, in _fail
    error.propagate()             
  File "/.../RecordFlux/rflx/error.py", line 162, in propagate
    raise self
rflx.error.FatalError: test.rflx:41:22: generator: error: unexpected Case with type universal integer (2 .. 256) in assignment
                                                                      
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