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------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                              S E M _ C H 5                               --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 1992-2011, Free Software Foundation, Inc.         --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license.          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------
 
with Aspects;  use Aspects;
with Atree;    use Atree;
with Checks;   use Checks;
with Einfo;    use Einfo;
with Errout;   use Errout;
with Expander; use Expander;
with Exp_Ch6;  use Exp_Ch6;
with Exp_Util; use Exp_Util;
with Freeze;   use Freeze;
with Lib;      use Lib;
with Lib.Xref; use Lib.Xref;
with Namet;    use Namet;
with Nlists;   use Nlists;
with Nmake;    use Nmake;
with Opt;      use Opt;
with Restrict; use Restrict;
with Rident;   use Rident;
with Rtsfind;  use Rtsfind;
with Sem;      use Sem;
with Sem_Aux;  use Sem_Aux;
with Sem_Case; use Sem_Case;
with Sem_Ch3;  use Sem_Ch3;
with Sem_Ch6;  use Sem_Ch6;
with Sem_Ch8;  use Sem_Ch8;
with Sem_Dim;  use Sem_Dim;
with Sem_Disp; use Sem_Disp;
with Sem_Elab; use Sem_Elab;
with Sem_Eval; use Sem_Eval;
with Sem_Res;  use Sem_Res;
with Sem_Type; use Sem_Type;
with Sem_Util; use Sem_Util;
with Sem_Warn; use Sem_Warn;
with Snames;   use Snames;
with Stand;    use Stand;
with Sinfo;    use Sinfo;
with Targparm; use Targparm;
with Tbuild;   use Tbuild;
with Uintp;    use Uintp;
 
package body Sem_Ch5 is
 
   Unblocked_Exit_Count : Nat := 0;
   --  This variable is used when processing if statements, case statements,
   --  and block statements. It counts the number of exit points that are not
   --  blocked by unconditional transfer instructions: for IF and CASE, these
   --  are the branches of the conditional; for a block, they are the statement
   --  sequence of the block, and the statement sequences of any exception
   --  handlers that are part of the block. When processing is complete, if
   --  this count is zero, it means that control cannot fall through the IF,
   --  CASE or block statement. This is used for the generation of warning
   --  messages. This variable is recursively saved on entry to processing the
   --  construct, and restored on exit.
 
   procedure Pre_Analyze_Range (R_Copy : Node_Id);
   --  Determine expected type of range or domain of iteration of Ada 2012
   --  loop by analyzing separate copy. Do the analysis and resolution of the
   --  copy of the bound(s) with expansion disabled, to prevent the generation
   --  of finalization actions. This prevents memory leaks when the bounds
   --  contain calls to functions returning controlled arrays or when the
   --  domain of iteration is a container.
 
   ------------------------
   -- Analyze_Assignment --
   ------------------------
 
   procedure Analyze_Assignment (N : Node_Id) is
      Lhs  : constant Node_Id := Name (N);
      Rhs  : constant Node_Id := Expression (N);
      T1   : Entity_Id;
      T2   : Entity_Id;
      Decl : Node_Id;
 
      procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
      --  N is the node for the left hand side of an assignment, and it is not
      --  a variable. This routine issues an appropriate diagnostic.
 
      procedure Kill_Lhs;
      --  This is called to kill current value settings of a simple variable
      --  on the left hand side. We call it if we find any error in analyzing
      --  the assignment, and at the end of processing before setting any new
      --  current values in place.
 
      procedure Set_Assignment_Type
        (Opnd      : Node_Id;
         Opnd_Type : in out Entity_Id);
      --  Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type is the
      --  nominal subtype. This procedure is used to deal with cases where the
      --  nominal subtype must be replaced by the actual subtype.
 
      -------------------------------
      -- Diagnose_Non_Variable_Lhs --
      -------------------------------
 
      procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
      begin
         --  Not worth posting another error if left hand side already flagged
         --  as being illegal in some respect.
 
         if Error_Posted (N) then
            return;
 
         --  Some special bad cases of entity names
 
         elsif Is_Entity_Name (N) then
            declare
               Ent : constant Entity_Id := Entity (N);
 
            begin
               if Ekind (Ent) = E_In_Parameter then
                  Error_Msg_N
                    ("assignment to IN mode parameter not allowed", N);
 
               --  Renamings of protected private components are turned into
               --  constants when compiling a protected function. In the case
               --  of single protected types, the private component appears
               --  directly.
 
               elsif (Is_Prival (Ent)
                        and then
                          (Ekind (Current_Scope) = E_Function
                             or else Ekind (Enclosing_Dynamic_Scope
                                             (Current_Scope)) = E_Function))
                   or else
                     (Ekind (Ent) = E_Component
                        and then Is_Protected_Type (Scope (Ent)))
               then
                  Error_Msg_N
                    ("protected function cannot modify protected object", N);
 
               elsif Ekind (Ent) = E_Loop_Parameter then
                  Error_Msg_N
                    ("assignment to loop parameter not allowed", N);
 
               else
                  Error_Msg_N
                    ("left hand side of assignment must be a variable", N);
               end if;
            end;
 
         --  For indexed components or selected components, test prefix
 
         elsif Nkind (N) = N_Indexed_Component then
            Diagnose_Non_Variable_Lhs (Prefix (N));
 
         --  Another special case for assignment to discriminant
 
         elsif Nkind (N) = N_Selected_Component then
            if Present (Entity (Selector_Name (N)))
              and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
            then
               Error_Msg_N
                 ("assignment to discriminant not allowed", N);
            else
               Diagnose_Non_Variable_Lhs (Prefix (N));
            end if;
 
         else
            --  If we fall through, we have no special message to issue!
 
            Error_Msg_N ("left hand side of assignment must be a variable", N);
         end if;
      end Diagnose_Non_Variable_Lhs;
 
      --------------
      -- Kill_LHS --
      --------------
 
      procedure Kill_Lhs is
      begin
         if Is_Entity_Name (Lhs) then
            declare
               Ent : constant Entity_Id := Entity (Lhs);
            begin
               if Present (Ent) then
                  Kill_Current_Values (Ent);
               end if;
            end;
         end if;
      end Kill_Lhs;
 
      -------------------------
      -- Set_Assignment_Type --
      -------------------------
 
      procedure Set_Assignment_Type
        (Opnd      : Node_Id;
         Opnd_Type : in out Entity_Id)
      is
      begin
         Require_Entity (Opnd);
 
         --  If the assignment operand is an in-out or out parameter, then we
         --  get the actual subtype (needed for the unconstrained case). If the
         --  operand is the actual in an entry declaration, then within the
         --  accept statement it is replaced with a local renaming, which may
         --  also have an actual subtype.
 
         if Is_Entity_Name (Opnd)
           and then (Ekind (Entity (Opnd)) = E_Out_Parameter
                      or else Ekind (Entity (Opnd)) =
                           E_In_Out_Parameter
                      or else Ekind (Entity (Opnd)) =
                           E_Generic_In_Out_Parameter
                      or else
                        (Ekind (Entity (Opnd)) = E_Variable
                          and then Nkind (Parent (Entity (Opnd))) =
                             N_Object_Renaming_Declaration
                          and then Nkind (Parent (Parent (Entity (Opnd)))) =
                             N_Accept_Statement))
         then
            Opnd_Type := Get_Actual_Subtype (Opnd);
 
         --  If assignment operand is a component reference, then we get the
         --  actual subtype of the component for the unconstrained case.
 
         elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
           and then not Is_Unchecked_Union (Opnd_Type)
         then
            Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
 
            if Present (Decl) then
               Insert_Action (N, Decl);
               Mark_Rewrite_Insertion (Decl);
               Analyze (Decl);
               Opnd_Type := Defining_Identifier (Decl);
               Set_Etype (Opnd, Opnd_Type);
               Freeze_Itype (Opnd_Type, N);
 
            elsif Is_Constrained (Etype (Opnd)) then
               Opnd_Type := Etype (Opnd);
            end if;
 
         --  For slice, use the constrained subtype created for the slice
 
         elsif Nkind (Opnd) = N_Slice then
            Opnd_Type := Etype (Opnd);
         end if;
      end Set_Assignment_Type;
 
   --  Start of processing for Analyze_Assignment
 
   begin
      Mark_Coextensions (N, Rhs);
 
      Analyze (Rhs);
      Analyze (Lhs);
 
      --  Ensure that we never do an assignment on a variable marked as
      --  as Safe_To_Reevaluate.
 
      pragma Assert (not Is_Entity_Name (Lhs)
        or else Ekind (Entity (Lhs)) /= E_Variable
        or else not Is_Safe_To_Reevaluate (Entity (Lhs)));
 
      --  Start type analysis for assignment
 
      T1 := Etype (Lhs);
 
      --  In the most general case, both Lhs and Rhs can be overloaded, and we
      --  must compute the intersection of the possible types on each side.
 
      if Is_Overloaded (Lhs) then
         declare
            I  : Interp_Index;
            It : Interp;
 
         begin
            T1 := Any_Type;
            Get_First_Interp (Lhs, I, It);
 
            while Present (It.Typ) loop
               if Has_Compatible_Type (Rhs, It.Typ) then
                  if T1 /= Any_Type then
 
                     --  An explicit dereference is overloaded if the prefix
                     --  is. Try to remove the ambiguity on the prefix, the
                     --  error will be posted there if the ambiguity is real.
 
                     if Nkind (Lhs) = N_Explicit_Dereference then
                        declare
                           PI    : Interp_Index;
                           PI1   : Interp_Index := 0;
                           PIt   : Interp;
                           Found : Boolean;
 
                        begin
                           Found := False;
                           Get_First_Interp (Prefix (Lhs), PI, PIt);
 
                           while Present (PIt.Typ) loop
                              if Is_Access_Type (PIt.Typ)
                                and then Has_Compatible_Type
                                           (Rhs, Designated_Type (PIt.Typ))
                              then
                                 if Found then
                                    PIt :=
                                      Disambiguate (Prefix (Lhs),
                                        PI1, PI, Any_Type);
 
                                    if PIt = No_Interp then
                                       Error_Msg_N
                                         ("ambiguous left-hand side"
                                            & " in assignment", Lhs);
                                       exit;
                                    else
                                       Resolve (Prefix (Lhs), PIt.Typ);
                                    end if;
 
                                    exit;
                                 else
                                    Found := True;
                                    PI1 := PI;
                                 end if;
                              end if;
 
                              Get_Next_Interp (PI, PIt);
                           end loop;
                        end;
 
                     else
                        Error_Msg_N
                          ("ambiguous left-hand side in assignment", Lhs);
                        exit;
                     end if;
                  else
                     T1 := It.Typ;
                  end if;
               end if;
 
               Get_Next_Interp (I, It);
            end loop;
         end;
 
         if T1 = Any_Type then
            Error_Msg_N
              ("no valid types for left-hand side for assignment", Lhs);
            Kill_Lhs;
            return;
         end if;
      end if;
 
      --  The resulting assignment type is T1, so now we will resolve the left
      --  hand side of the assignment using this determined type.
 
      Resolve (Lhs, T1);
 
      --  Cases where Lhs is not a variable
 
      if not Is_Variable (Lhs) then
 
         --  Ada 2005 (AI-327): Check assignment to the attribute Priority of a
         --  protected object.
 
         declare
            Ent : Entity_Id;
            S   : Entity_Id;
 
         begin
            if Ada_Version >= Ada_2005 then
 
               --  Handle chains of renamings
 
               Ent := Lhs;
               while Nkind (Ent) in N_Has_Entity
                 and then Present (Entity (Ent))
                 and then Present (Renamed_Object (Entity (Ent)))
               loop
                  Ent := Renamed_Object (Entity (Ent));
               end loop;
 
               if (Nkind (Ent) = N_Attribute_Reference
                     and then Attribute_Name (Ent) = Name_Priority)
 
                  --  Renamings of the attribute Priority applied to protected
                  --  objects have been previously expanded into calls to the
                  --  Get_Ceiling run-time subprogram.
 
                 or else
                  (Nkind (Ent) = N_Function_Call
                     and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
                                or else
                               Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
               then
                  --  The enclosing subprogram cannot be a protected function
 
                  S := Current_Scope;
                  while not (Is_Subprogram (S)
                               and then Convention (S) = Convention_Protected)
                     and then S /= Standard_Standard
                  loop
                     S := Scope (S);
                  end loop;
 
                  if Ekind (S) = E_Function
                    and then Convention (S) = Convention_Protected
                  then
                     Error_Msg_N
                       ("protected function cannot modify protected object",
                        Lhs);
                  end if;
 
                  --  Changes of the ceiling priority of the protected object
                  --  are only effective if the Ceiling_Locking policy is in
                  --  effect (AARM D.5.2 (5/2)).
 
                  if Locking_Policy /= 'C' then
                     Error_Msg_N ("assignment to the attribute PRIORITY has " &
                                  "no effect?", Lhs);
                     Error_Msg_N ("\since no Locking_Policy has been " &
                                  "specified", Lhs);
                  end if;
 
                  return;
               end if;
            end if;
         end;
 
         Diagnose_Non_Variable_Lhs (Lhs);
         return;
 
      --  Error of assigning to limited type. We do however allow this in
      --  certain cases where the front end generates the assignments.
 
      elsif Is_Limited_Type (T1)
        and then not Assignment_OK (Lhs)
        and then not Assignment_OK (Original_Node (Lhs))
        and then not Is_Value_Type (T1)
      then
         --  CPP constructors can only be called in declarations
 
         if Is_CPP_Constructor_Call (Rhs) then
            Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
         else
            Error_Msg_N
              ("left hand of assignment must not be limited type", Lhs);
            Explain_Limited_Type (T1, Lhs);
         end if;
         return;
 
      --  Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
      --  abstract. This is only checked when the assignment Comes_From_Source,
      --  because in some cases the expander generates such assignments (such
      --  in the _assign operation for an abstract type).
 
      elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then
         Error_Msg_N
           ("target of assignment operation must not be abstract", Lhs);
      end if;
 
      --  Resolution may have updated the subtype, in case the left-hand side
      --  is a private protected component. Use the correct subtype to avoid
      --  scoping issues in the back-end.
 
      T1 := Etype (Lhs);
 
      --  Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
      --  type. For example:
 
      --    limited with P;
      --    package Pkg is
      --      type Acc is access P.T;
      --    end Pkg;
 
      --    with Pkg; use Acc;
      --    procedure Example is
      --       A, B : Acc;
      --    begin
      --       A.all := B.all;  -- ERROR
      --    end Example;
 
      if Nkind (Lhs) = N_Explicit_Dereference
        and then Ekind (T1) = E_Incomplete_Type
      then
         Error_Msg_N ("invalid use of incomplete type", Lhs);
         Kill_Lhs;
         return;
      end if;
 
      --  Now we can complete the resolution of the right hand side
 
      Set_Assignment_Type (Lhs, T1);
      Resolve (Rhs, T1);
 
      --  This is the point at which we check for an unset reference
 
      Check_Unset_Reference (Rhs);
      Check_Unprotected_Access (Lhs, Rhs);
 
      --  Remaining steps are skipped if Rhs was syntactically in error
 
      if Rhs = Error then
         Kill_Lhs;
         return;
      end if;
 
      T2 := Etype (Rhs);
 
      if not Covers (T1, T2) then
         Wrong_Type (Rhs, Etype (Lhs));
         Kill_Lhs;
         return;
      end if;
 
      --  Ada 2005 (AI-326): In case of explicit dereference of incomplete
      --  types, use the non-limited view if available
 
      if Nkind (Rhs) = N_Explicit_Dereference
        and then Ekind (T2) = E_Incomplete_Type
        and then Is_Tagged_Type (T2)
        and then Present (Non_Limited_View (T2))
      then
         T2 := Non_Limited_View (T2);
      end if;
 
      Set_Assignment_Type (Rhs, T2);
 
      if Total_Errors_Detected /= 0 then
         if No (T1) then
            T1 := Any_Type;
         end if;
 
         if No (T2) then
            T2 := Any_Type;
         end if;
      end if;
 
      if T1 = Any_Type or else T2 = Any_Type then
         Kill_Lhs;
         return;
      end if;
 
      --  If the rhs is class-wide or dynamically tagged, then require the lhs
      --  to be class-wide. The case where the rhs is a dynamically tagged call
      --  to a dispatching operation with a controlling access result is
      --  excluded from this check, since the target has an access type (and
      --  no tag propagation occurs in that case).
 
      if (Is_Class_Wide_Type (T2)
           or else (Is_Dynamically_Tagged (Rhs)
                     and then not Is_Access_Type (T1)))
        and then not Is_Class_Wide_Type (T1)
      then
         Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
 
      elsif Is_Class_Wide_Type (T1)
        and then not Is_Class_Wide_Type (T2)
        and then not Is_Tag_Indeterminate (Rhs)
        and then not Is_Dynamically_Tagged (Rhs)
      then
         Error_Msg_N ("dynamically tagged expression required!", Rhs);
      end if;
 
      --  Propagate the tag from a class-wide target to the rhs when the rhs
      --  is a tag-indeterminate call.
 
      if Is_Tag_Indeterminate (Rhs) then
         if Is_Class_Wide_Type (T1) then
            Propagate_Tag (Lhs, Rhs);
 
         elsif Nkind (Rhs) = N_Function_Call
              and then Is_Entity_Name (Name (Rhs))
              and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
         then
            Error_Msg_N
              ("call to abstract function must be dispatching", Name (Rhs));
 
         elsif Nkind (Rhs) = N_Qualified_Expression
           and then Nkind (Expression (Rhs)) = N_Function_Call
              and then Is_Entity_Name (Name (Expression (Rhs)))
              and then
                Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
         then
            Error_Msg_N
              ("call to abstract function must be dispatching",
                Name (Expression (Rhs)));
         end if;
      end if;
 
      --  Ada 2005 (AI-385): When the lhs type is an anonymous access type,
      --  apply an implicit conversion of the rhs to that type to force
      --  appropriate static and run-time accessibility checks. This applies
      --  as well to anonymous access-to-subprogram types that are component
      --  subtypes or formal parameters.
 
      if Ada_Version >= Ada_2005
        and then Is_Access_Type (T1)
      then
         if Is_Local_Anonymous_Access (T1)
           or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
 
           --  Handle assignment to an Ada 2012 stand-alone object
           --  of an anonymous access type.
 
           or else (Ekind (T1) = E_Anonymous_Access_Type
                     and then Nkind (Associated_Node_For_Itype (T1)) =
                                                       N_Object_Declaration)
 
         then
            Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
            Analyze_And_Resolve (Rhs, T1);
         end if;
      end if;
 
      --  Ada 2005 (AI-231): Assignment to not null variable
 
      if Ada_Version >= Ada_2005
        and then Can_Never_Be_Null (T1)
        and then not Assignment_OK (Lhs)
      then
         --  Case where we know the right hand side is null
 
         if Known_Null (Rhs) then
            Apply_Compile_Time_Constraint_Error
              (N   => Rhs,
               Msg => "(Ada 2005) null not allowed in null-excluding objects?",
               Reason => CE_Null_Not_Allowed);
 
            --  We still mark this as a possible modification, that's necessary
            --  to reset Is_True_Constant, and desirable for xref purposes.
 
            Note_Possible_Modification (Lhs, Sure => True);
            return;
 
         --  If we know the right hand side is non-null, then we convert to the
         --  target type, since we don't need a run time check in that case.
 
         elsif not Can_Never_Be_Null (T2) then
            Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
            Analyze_And_Resolve (Rhs, T1);
         end if;
      end if;
 
      if Is_Scalar_Type (T1) then
         Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
 
      --  For array types, verify that lengths match. If the right hand side
      --  is a function call that has been inlined, the assignment has been
      --  rewritten as a block, and the constraint check will be applied to the
      --  assignment within the block.
 
      elsif Is_Array_Type (T1)
        and then
          (Nkind (Rhs) /= N_Type_Conversion
            or else Is_Constrained (Etype (Rhs)))
        and then
          (Nkind (Rhs) /= N_Function_Call
            or else Nkind (N) /= N_Block_Statement)
      then
         --  Assignment verifies that the length of the Lsh and Rhs are equal,
         --  but of course the indexes do not have to match. If the right-hand
         --  side is a type conversion to an unconstrained type, a length check
         --  is performed on the expression itself during expansion. In rare
         --  cases, the redundant length check is computed on an index type
         --  with a different representation, triggering incorrect code in the
         --  back end.
 
         Apply_Length_Check (Rhs, Etype (Lhs));
 
      else
         --  Discriminant checks are applied in the course of expansion
 
         null;
      end if;
 
      --  Note: modifications of the Lhs may only be recorded after
      --  checks have been applied.
 
      Note_Possible_Modification (Lhs, Sure => True);
      Check_Order_Dependence;
 
      --  ??? a real accessibility check is needed when ???
 
      --  Post warning for redundant assignment or variable to itself
 
      if Warn_On_Redundant_Constructs
 
         --  We only warn for source constructs
 
         and then Comes_From_Source (N)
 
         --  Where the object is the same on both sides
 
         and then Same_Object (Lhs, Original_Node (Rhs))
 
         --  But exclude the case where the right side was an operation that
         --  got rewritten (e.g. JUNK + K, where K was known to be zero). We
         --  don't want to warn in such a case, since it is reasonable to write
         --  such expressions especially when K is defined symbolically in some
         --  other package.
 
        and then Nkind (Original_Node (Rhs)) not in N_Op
      then
         if Nkind (Lhs) in N_Has_Entity then
            Error_Msg_NE -- CODEFIX
              ("?useless assignment of & to itself!", N, Entity (Lhs));
         else
            Error_Msg_N -- CODEFIX
              ("?useless assignment of object to itself!", N);
         end if;
      end if;
 
      --  Check for non-allowed composite assignment
 
      if not Support_Composite_Assign_On_Target
        and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
        and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
      then
         Error_Msg_CRT ("composite assignment", N);
      end if;
 
      --  Check elaboration warning for left side if not in elab code
 
      if not In_Subprogram_Or_Concurrent_Unit then
         Check_Elab_Assign (Lhs);
      end if;
 
      --  Set Referenced_As_LHS if appropriate. We only set this flag if the
      --  assignment is a source assignment in the extended main source unit.
      --  We are not interested in any reference information outside this
      --  context, or in compiler generated assignment statements.
 
      if Comes_From_Source (N)
        and then In_Extended_Main_Source_Unit (Lhs)
      then
         Set_Referenced_Modified (Lhs, Out_Param => False);
      end if;
 
      --  Final step. If left side is an entity, then we may be able to reset
      --  the current tracked values to new safe values. We only have something
      --  to do if the left side is an entity name, and expansion has not
      --  modified the node into something other than an assignment, and of
      --  course we only capture values if it is safe to do so.
 
      if Is_Entity_Name (Lhs)
        and then Nkind (N) = N_Assignment_Statement
      then
         declare
            Ent : constant Entity_Id := Entity (Lhs);
 
         begin
            if Safe_To_Capture_Value (N, Ent) then
 
               --  If simple variable on left side, warn if this assignment
               --  blots out another one (rendering it useless). We only do
               --  this for source assignments, otherwise we can generate bogus
               --  warnings when an assignment is rewritten as another
               --  assignment, and gets tied up with itself.
 
               if Warn_On_Modified_Unread
                 and then Is_Assignable (Ent)
                 and then Comes_From_Source (N)
                 and then In_Extended_Main_Source_Unit (Ent)
               then
                  Warn_On_Useless_Assignment (Ent, N);
               end if;
 
               --  If we are assigning an access type and the left side is an
               --  entity, then make sure that the Is_Known_[Non_]Null flags
               --  properly reflect the state of the entity after assignment.
 
               if Is_Access_Type (T1) then
                  if Known_Non_Null (Rhs) then
                     Set_Is_Known_Non_Null (Ent, True);
 
                  elsif Known_Null (Rhs)
                    and then not Can_Never_Be_Null (Ent)
                  then
                     Set_Is_Known_Null (Ent, True);
 
                  else
                     Set_Is_Known_Null (Ent, False);
 
                     if not Can_Never_Be_Null (Ent) then
                        Set_Is_Known_Non_Null (Ent, False);
                     end if;
                  end if;
 
               --  For discrete types, we may be able to set the current value
               --  if the value is known at compile time.
 
               elsif Is_Discrete_Type (T1)
                 and then Compile_Time_Known_Value (Rhs)
               then
                  Set_Current_Value (Ent, Rhs);
               else
                  Set_Current_Value (Ent, Empty);
               end if;
 
            --  If not safe to capture values, kill them
 
            else
               Kill_Lhs;
            end if;
         end;
      end if;
 
      --  If assigning to an object in whole or in part, note location of
      --  assignment in case no one references value. We only do this for
      --  source assignments, otherwise we can generate bogus warnings when an
      --  assignment is rewritten as another assignment, and gets tied up with
      --  itself.
 
      declare
         Ent : constant Entity_Id := Get_Enclosing_Object (Lhs);
      begin
         if Present (Ent)
           and then Safe_To_Capture_Value (N, Ent)
           and then Nkind (N) = N_Assignment_Statement
           and then Warn_On_Modified_Unread
           and then Is_Assignable (Ent)
           and then Comes_From_Source (N)
           and then In_Extended_Main_Source_Unit (Ent)
         then
            Set_Last_Assignment (Ent, Lhs);
         end if;
      end;
 
      Analyze_Dimension (N);
   end Analyze_Assignment;
 
   -----------------------------
   -- Analyze_Block_Statement --
   -----------------------------
 
   procedure Analyze_Block_Statement (N : Node_Id) is
      procedure Install_Return_Entities (Scop : Entity_Id);
      --  Install all entities of return statement scope Scop in the visibility
      --  chain except for the return object since its entity is reused in a
      --  renaming.
 
      -----------------------------
      -- Install_Return_Entities --
      -----------------------------
 
      procedure Install_Return_Entities (Scop : Entity_Id) is
         Id : Entity_Id;
 
      begin
         Id := First_Entity (Scop);
         while Present (Id) loop
 
            --  Do not install the return object
 
            if not Ekind_In (Id, E_Constant, E_Variable)
              or else not Is_Return_Object (Id)
            then
               Install_Entity (Id);
            end if;
 
            Next_Entity (Id);
         end loop;
      end Install_Return_Entities;
 
      --  Local constants and variables
 
      Decls : constant List_Id := Declarations (N);
      Id    : constant Node_Id := Identifier (N);
      HSS   : constant Node_Id := Handled_Statement_Sequence (N);
 
      Is_BIP_Return_Statement : Boolean;
 
   --  Start of processing for Analyze_Block_Statement
 
   begin
      --  In SPARK mode, we reject block statements. Note that the case of
      --  block statements generated by the expander is fine.
 
      if Nkind (Original_Node (N)) = N_Block_Statement then
         Check_SPARK_Restriction ("block statement is not allowed", N);
      end if;
 
      --  If no handled statement sequence is present, things are really messed
      --  up, and we just return immediately (defence against previous errors).
 
      if No (HSS) then
         return;
      end if;
 
      --  Detect whether the block is actually a rewritten return statement of
      --  a build-in-place function.
 
      Is_BIP_Return_Statement :=
        Present (Id)
          and then Present (Entity (Id))
          and then Ekind (Entity (Id)) = E_Return_Statement
          and then Is_Build_In_Place_Function
                     (Return_Applies_To (Entity (Id)));
 
      --  Normal processing with HSS present
 
      declare
         EH  : constant List_Id := Exception_Handlers (HSS);
         Ent : Entity_Id        := Empty;
         S   : Entity_Id;
 
         Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
         --  Recursively save value of this global, will be restored on exit
 
      begin
         --  Initialize unblocked exit count for statements of begin block
         --  plus one for each exception handler that is present.
 
         Unblocked_Exit_Count := 1;
 
         if Present (EH) then
            Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
         end if;
 
         --  If a label is present analyze it and mark it as referenced
 
         if Present (Id) then
            Analyze (Id);
            Ent := Entity (Id);
 
            --  An error defense. If we have an identifier, but no entity, then
            --  something is wrong. If previous errors, then just remove the
            --  identifier and continue, otherwise raise an exception.
 
            if No (Ent) then
               if Total_Errors_Detected /= 0 then
                  Set_Identifier (N, Empty);
               else
                  raise Program_Error;
               end if;
 
            else
               Set_Ekind (Ent, E_Block);
               Generate_Reference (Ent, N, ' ');
               Generate_Definition (Ent);
 
               if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
                  Set_Label_Construct (Parent (Ent), N);
               end if;
            end if;
         end if;
 
         --  If no entity set, create a label entity
 
         if No (Ent) then
            Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
            Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
            Set_Parent (Ent, N);
         end if;
 
         Set_Etype (Ent, Standard_Void_Type);
         Set_Block_Node (Ent, Identifier (N));
         Push_Scope (Ent);
 
         --  The block served as an extended return statement. Ensure that any
         --  entities created during the analysis and expansion of the return
         --  object declaration are once again visible.
 
         if Is_BIP_Return_Statement then
            Install_Return_Entities (Ent);
         end if;
 
         if Present (Decls) then
            Analyze_Declarations (Decls);
            Check_Completion;
            Inspect_Deferred_Constant_Completion (Decls);
         end if;
 
         Analyze (HSS);
         Process_End_Label (HSS, 'e', Ent);
 
         --  If exception handlers are present, then we indicate that enclosing
         --  scopes contain a block with handlers. We only need to mark non-
         --  generic scopes.
 
         if Present (EH) then
            S := Scope (Ent);
            loop
               Set_Has_Nested_Block_With_Handler (S);
               exit when Is_Overloadable (S)
                 or else Ekind (S) = E_Package
                 or else Is_Generic_Unit (S);
               S := Scope (S);
            end loop;
         end if;
 
         Check_References (Ent);
         Warn_On_Useless_Assignments (Ent);
         End_Scope;
 
         if Unblocked_Exit_Count = 0 then
            Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
            Check_Unreachable_Code (N);
         else
            Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
         end if;
      end;
   end Analyze_Block_Statement;
 
   ----------------------------
   -- Analyze_Case_Statement --
   ----------------------------
 
   procedure Analyze_Case_Statement (N : Node_Id) is
      Exp            : Node_Id;
      Exp_Type       : Entity_Id;
      Exp_Btype      : Entity_Id;
      Last_Choice    : Nat;
      Dont_Care      : Boolean;
      Others_Present : Boolean;
 
      pragma Warnings (Off, Last_Choice);
      pragma Warnings (Off, Dont_Care);
      --  Don't care about assigned values
 
      Statements_Analyzed : Boolean := False;
      --  Set True if at least some statement sequences get analyzed. If False
      --  on exit, means we had a serious error that prevented full analysis of
      --  the case statement, and as a result it is not a good idea to output
      --  warning messages about unreachable code.
 
      Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
      --  Recursively save value of this global, will be restored on exit
 
      procedure Non_Static_Choice_Error (Choice : Node_Id);
      --  Error routine invoked by the generic instantiation below when the
      --  case statement has a non static choice.
 
      procedure Process_Statements (Alternative : Node_Id);
      --  Analyzes all the statements associated with a case alternative.
      --  Needed by the generic instantiation below.
 
      package Case_Choices_Processing is new
        Generic_Choices_Processing
          (Get_Alternatives          => Alternatives,
           Get_Choices               => Discrete_Choices,
           Process_Empty_Choice      => No_OP,
           Process_Non_Static_Choice => Non_Static_Choice_Error,
           Process_Associated_Node   => Process_Statements);
      use Case_Choices_Processing;
      --  Instantiation of the generic choice processing package
 
      -----------------------------
      -- Non_Static_Choice_Error --
      -----------------------------
 
      procedure Non_Static_Choice_Error (Choice : Node_Id) is
      begin
         Flag_Non_Static_Expr
           ("choice given in case statement is not static!", Choice);
      end Non_Static_Choice_Error;
 
      ------------------------
      -- Process_Statements --
      ------------------------
 
      procedure Process_Statements (Alternative : Node_Id) is
         Choices : constant List_Id := Discrete_Choices (Alternative);
         Ent     : Entity_Id;
 
      begin
         Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
         Statements_Analyzed := True;
 
         --  An interesting optimization. If the case statement expression
         --  is a simple entity, then we can set the current value within an
         --  alternative if the alternative has one possible value.
 
         --    case N is
         --      when 1      => alpha
         --      when 2 | 3  => beta
         --      when others => gamma
 
         --  Here we know that N is initially 1 within alpha, but for beta and
         --  gamma, we do not know anything more about the initial value.
 
         if Is_Entity_Name (Exp) then
            Ent := Entity (Exp);
 
            if Ekind_In (Ent, E_Variable,
                              E_In_Out_Parameter,
                              E_Out_Parameter)
            then
               if List_Length (Choices) = 1
                 and then Nkind (First (Choices)) in N_Subexpr
                 and then Compile_Time_Known_Value (First (Choices))
               then
                  Set_Current_Value (Entity (Exp), First (Choices));
               end if;
 
               Analyze_Statements (Statements (Alternative));
 
               --  After analyzing the case, set the current value to empty
               --  since we won't know what it is for the next alternative
               --  (unless reset by this same circuit), or after the case.
 
               Set_Current_Value (Entity (Exp), Empty);
               return;
            end if;
         end if;
 
         --  Case where expression is not an entity name of a variable
 
         Analyze_Statements (Statements (Alternative));
      end Process_Statements;
 
   --  Start of processing for Analyze_Case_Statement
 
   begin
      Unblocked_Exit_Count := 0;
      Exp := Expression (N);
      Analyze (Exp);
 
      --  The expression must be of any discrete type. In rare cases, the
      --  expander constructs a case statement whose expression has a private
      --  type whose full view is discrete. This can happen when generating
      --  a stream operation for a variant type after the type is frozen,
      --  when the partial of view of the type of the discriminant is private.
      --  In that case, use the full view to analyze case alternatives.
 
      if not Is_Overloaded (Exp)
        and then not Comes_From_Source (N)
        and then Is_Private_Type (Etype (Exp))
        and then Present (Full_View (Etype (Exp)))
        and then Is_Discrete_Type (Full_View (Etype (Exp)))
      then
         Resolve (Exp, Etype (Exp));
         Exp_Type := Full_View (Etype (Exp));
 
      else
         Analyze_And_Resolve (Exp, Any_Discrete);
         Exp_Type := Etype (Exp);
      end if;
 
      Check_Unset_Reference (Exp);
      Exp_Btype := Base_Type (Exp_Type);
 
      --  The expression must be of a discrete type which must be determinable
      --  independently of the context in which the expression occurs, but
      --  using the fact that the expression must be of a discrete type.
      --  Moreover, the type this expression must not be a character literal
      --  (which is always ambiguous) or, for Ada-83, a generic formal type.
 
      --  If error already reported by Resolve, nothing more to do
 
      if Exp_Btype = Any_Discrete
        or else Exp_Btype = Any_Type
      then
         return;
 
      elsif Exp_Btype = Any_Character then
         Error_Msg_N
           ("character literal as case expression is ambiguous", Exp);
         return;
 
      elsif Ada_Version = Ada_83
        and then (Is_Generic_Type (Exp_Btype)
                    or else Is_Generic_Type (Root_Type (Exp_Btype)))
      then
         Error_Msg_N
           ("(Ada 83) case expression cannot be of a generic type", Exp);
         return;
      end if;
 
      --  If the case expression is a formal object of mode in out, then treat
      --  it as having a nonstatic subtype by forcing use of the base type
      --  (which has to get passed to Check_Case_Choices below). Also use base
      --  type when the case expression is parenthesized.
 
      if Paren_Count (Exp) > 0
        or else (Is_Entity_Name (Exp)
                  and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
      then
         Exp_Type := Exp_Btype;
      end if;
 
      --  Call instantiated Analyze_Choices which does the rest of the work
 
      Analyze_Choices (N, Exp_Type, Dont_Care, Others_Present);
 
      --  A case statement with a single OTHERS alternative is not allowed
      --  in SPARK.
 
      if Others_Present
        and then List_Length (Alternatives (N)) = 1
      then
         Check_SPARK_Restriction
           ("OTHERS as unique case alternative is not allowed", N);
      end if;
 
      if Exp_Type = Universal_Integer and then not Others_Present then
         Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
      end if;
 
      --  If all our exits were blocked by unconditional transfers of control,
      --  then the entire CASE statement acts as an unconditional transfer of
      --  control, so treat it like one, and check unreachable code. Skip this
      --  test if we had serious errors preventing any statement analysis.
 
      if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
         Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
         Check_Unreachable_Code (N);
      else
         Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
      end if;
 
      if not Expander_Active
        and then Compile_Time_Known_Value (Expression (N))
        and then Serious_Errors_Detected = 0
      then
         declare
            Chosen : constant Node_Id := Find_Static_Alternative (N);
            Alt    : Node_Id;
 
         begin
            Alt := First (Alternatives (N));
            while Present (Alt) loop
               if Alt /= Chosen then
                  Remove_Warning_Messages (Statements (Alt));
               end if;
 
               Next (Alt);
            end loop;
         end;
      end if;
   end Analyze_Case_Statement;
 
   ----------------------------
   -- Analyze_Exit_Statement --
   ----------------------------
 
   --  If the exit includes a name, it must be the name of a currently open
   --  loop. Otherwise there must be an innermost open loop on the stack, to
   --  which the statement implicitly refers.
 
   --  Additionally, in SPARK mode:
 
   --    The exit can only name the closest enclosing loop;
 
   --    An exit with a when clause must be directly contained in a loop;
 
   --    An exit without a when clause must be directly contained in an
   --    if-statement with no elsif or else, which is itself directly contained
   --    in a loop. The exit must be the last statement in the if-statement.
 
   procedure Analyze_Exit_Statement (N : Node_Id) is
      Target   : constant Node_Id := Name (N);
      Cond     : constant Node_Id := Condition (N);
      Scope_Id : Entity_Id;
      U_Name   : Entity_Id;
      Kind     : Entity_Kind;
 
   begin
      if No (Cond) then
         Check_Unreachable_Code (N);
      end if;
 
      if Present (Target) then
         Analyze (Target);
         U_Name := Entity (Target);
 
         if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
            Error_Msg_N ("invalid loop name in exit statement", N);
            return;
 
         else
            if Has_Loop_In_Inner_Open_Scopes (U_Name) then
               Check_SPARK_Restriction
                 ("exit label must name the closest enclosing loop", N);
            end if;
 
            Set_Has_Exit (U_Name);
         end if;
 
      else
         U_Name := Empty;
      end if;
 
      for J in reverse 0 .. Scope_Stack.Last loop
         Scope_Id := Scope_Stack.Table (J).Entity;
         Kind := Ekind (Scope_Id);
 
         if Kind = E_Loop
           and then (No (Target) or else Scope_Id = U_Name)
         then
            Set_Has_Exit (Scope_Id);
            exit;
 
         elsif Kind = E_Block
           or else Kind = E_Loop
           or else Kind = E_Return_Statement
         then
            null;
 
         else
            Error_Msg_N
              ("cannot exit from program unit or accept statement", N);
            return;
         end if;
      end loop;
 
      --  Verify that if present the condition is a Boolean expression
 
      if Present (Cond) then
         Analyze_And_Resolve (Cond, Any_Boolean);
         Check_Unset_Reference (Cond);
      end if;
 
      --  In SPARK mode, verify that the exit statement respects the SPARK
      --  restrictions.
 
      if Present (Cond) then
         if Nkind (Parent (N)) /= N_Loop_Statement then
            Check_SPARK_Restriction
              ("exit with when clause must be directly in loop", N);
         end if;
 
      else
         if Nkind (Parent (N)) /= N_If_Statement then
            if Nkind (Parent (N)) = N_Elsif_Part then
               Check_SPARK_Restriction
                 ("exit must be in IF without ELSIF", N);
            else
               Check_SPARK_Restriction ("exit must be directly in IF", N);
            end if;
 
         elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then
            Check_SPARK_Restriction
              ("exit must be in IF directly in loop", N);
 
         --  First test the presence of ELSE, so that an exit in an ELSE leads
         --  to an error mentioning the ELSE.
 
         elsif Present (Else_Statements (Parent (N))) then
            Check_SPARK_Restriction ("exit must be in IF without ELSE", N);
 
         --  An exit in an ELSIF does not reach here, as it would have been
         --  detected in the case (Nkind (Parent (N)) /= N_If_Statement).
 
         elsif Present (Elsif_Parts (Parent (N))) then
            Check_SPARK_Restriction ("exit must be in IF without ELSIF", N);
         end if;
      end if;
 
      --  Chain exit statement to associated loop entity
 
      Set_Next_Exit_Statement  (N, First_Exit_Statement (Scope_Id));
      Set_First_Exit_Statement (Scope_Id, N);
 
      --  Since the exit may take us out of a loop, any previous assignment
      --  statement is not useless, so clear last assignment indications. It
      --  is OK to keep other current values, since if the exit statement
      --  does not exit, then the current values are still valid.
 
      Kill_Current_Values (Last_Assignment_Only => True);
   end Analyze_Exit_Statement;
 
   ----------------------------
   -- Analyze_Goto_Statement --
   ----------------------------
 
   procedure Analyze_Goto_Statement (N : Node_Id) is
      Label       : constant Node_Id := Name (N);
      Scope_Id    : Entity_Id;
      Label_Scope : Entity_Id;
      Label_Ent   : Entity_Id;
 
   begin
      Check_SPARK_Restriction ("goto statement is not allowed", N);
 
      --  Actual semantic checks
 
      Check_Unreachable_Code (N);
      Kill_Current_Values (Last_Assignment_Only => True);
 
      Analyze (Label);
      Label_Ent := Entity (Label);
 
      --  Ignore previous error
 
      if Label_Ent = Any_Id then
         return;
 
      --  We just have a label as the target of a goto
 
      elsif Ekind (Label_Ent) /= E_Label then
         Error_Msg_N ("target of goto statement must be a label", Label);
         return;
 
      --  Check that the target of the goto is reachable according to Ada
      --  scoping rules. Note: the special gotos we generate for optimizing
      --  local handling of exceptions would violate these rules, but we mark
      --  such gotos as analyzed when built, so this code is never entered.
 
      elsif not Reachable (Label_Ent) then
         Error_Msg_N ("target of goto statement is not reachable", Label);
         return;
      end if;
 
      --  Here if goto passes initial validity checks
 
      Label_Scope := Enclosing_Scope (Label_Ent);
 
      for J in reverse 0 .. Scope_Stack.Last loop
         Scope_Id := Scope_Stack.Table (J).Entity;
 
         if Label_Scope = Scope_Id
           or else (Ekind (Scope_Id) /= E_Block
                     and then Ekind (Scope_Id) /= E_Loop
                     and then Ekind (Scope_Id) /= E_Return_Statement)
         then
            if Scope_Id /= Label_Scope then
               Error_Msg_N
                 ("cannot exit from program unit or accept statement", N);
            end if;
 
            return;
         end if;
      end loop;
 
      raise Program_Error;
   end Analyze_Goto_Statement;
 
   --------------------------
   -- Analyze_If_Statement --
   --------------------------
 
   --  A special complication arises in the analysis of if statements
 
   --  The expander has circuitry to completely delete code that it can tell
   --  will not be executed (as a result of compile time known conditions). In
   --  the analyzer, we ensure that code that will be deleted in this manner is
   --  analyzed but not expanded. This is obviously more efficient, but more
   --  significantly, difficulties arise if code is expanded and then
   --  eliminated (e.g. exception table entries disappear). Similarly, itypes
   --  generated in deleted code must be frozen from start, because the nodes
   --  on which they depend will not be available at the freeze point.
 
   procedure Analyze_If_Statement (N : Node_Id) is
      E : Node_Id;
 
      Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
      --  Recursively save value of this global, will be restored on exit
 
      Save_In_Deleted_Code : Boolean;
 
      Del : Boolean := False;
      --  This flag gets set True if a True condition has been found, which
      --  means that remaining ELSE/ELSIF parts are deleted.
 
      procedure Analyze_Cond_Then (Cnode : Node_Id);
      --  This is applied to either the N_If_Statement node itself or to an
      --  N_Elsif_Part node. It deals with analyzing the condition and the THEN
      --  statements associated with it.
 
      -----------------------
      -- Analyze_Cond_Then --
      -----------------------
 
      procedure Analyze_Cond_Then (Cnode : Node_Id) is
         Cond : constant Node_Id := Condition (Cnode);
         Tstm : constant List_Id := Then_Statements (Cnode);
 
      begin
         Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
         Analyze_And_Resolve (Cond, Any_Boolean);
         Check_Unset_Reference (Cond);
         Set_Current_Value_Condition (Cnode);
 
         --  If already deleting, then just analyze then statements
 
         if Del then
            Analyze_Statements (Tstm);
 
         --  Compile time known value, not deleting yet
 
         elsif Compile_Time_Known_Value (Cond) then
            Save_In_Deleted_Code := In_Deleted_Code;
 
            --  If condition is True, then analyze the THEN statements and set
            --  no expansion for ELSE and ELSIF parts.
 
            if Is_True (Expr_Value (Cond)) then
               Analyze_Statements (Tstm);
               Del := True;
               Expander_Mode_Save_And_Set (False);
               In_Deleted_Code := True;
 
            --  If condition is False, analyze THEN with expansion off
 
            else -- Is_False (Expr_Value (Cond))
               Expander_Mode_Save_And_Set (False);
               In_Deleted_Code := True;
               Analyze_Statements (Tstm);
               Expander_Mode_Restore;
               In_Deleted_Code := Save_In_Deleted_Code;
            end if;
 
         --  Not known at compile time, not deleting, normal analysis
 
         else
            Analyze_Statements (Tstm);
         end if;
      end Analyze_Cond_Then;
 
   --  Start of Analyze_If_Statement
 
   begin
      --  Initialize exit count for else statements. If there is no else part,
      --  this count will stay non-zero reflecting the fact that the uncovered
      --  else case is an unblocked exit.
 
      Unblocked_Exit_Count := 1;
      Analyze_Cond_Then (N);
 
      --  Now to analyze the elsif parts if any are present
 
      if Present (Elsif_Parts (N)) then
         E := First (Elsif_Parts (N));
         while Present (E) loop
            Analyze_Cond_Then (E);
            Next (E);
         end loop;
      end if;
 
      if Present (Else_Statements (N)) then
         Analyze_Statements (Else_Statements (N));
      end if;
 
      --  If all our exits were blocked by unconditional transfers of control,
      --  then the entire IF statement acts as an unconditional transfer of
      --  control, so treat it like one, and check unreachable code.
 
      if Unblocked_Exit_Count = 0 then
         Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
         Check_Unreachable_Code (N);
      else
         Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
      end if;
 
      if Del then
         Expander_Mode_Restore;
         In_Deleted_Code := Save_In_Deleted_Code;
      end if;
 
      if not Expander_Active
        and then Compile_Time_Known_Value (Condition (N))
        and then Serious_Errors_Detected = 0
      then
         if Is_True (Expr_Value (Condition (N))) then
            Remove_Warning_Messages (Else_Statements (N));
 
            if Present (Elsif_Parts (N)) then
               E := First (Elsif_Parts (N));
               while Present (E) loop
                  Remove_Warning_Messages (Then_Statements (E));
                  Next (E);
               end loop;
            end if;
 
         else
            Remove_Warning_Messages (Then_Statements (N));
         end if;
      end if;
   end Analyze_If_Statement;
 
   ----------------------------------------
   -- Analyze_Implicit_Label_Declaration --
   ----------------------------------------
 
   --  An implicit label declaration is generated in the innermost enclosing
   --  declarative part. This is done for labels, and block and loop names.
 
   --  Note: any changes in this routine may need to be reflected in
   --  Analyze_Label_Entity.
 
   procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
      Id : constant Node_Id := Defining_Identifier (N);
   begin
      Enter_Name          (Id);
      Set_Ekind           (Id, E_Label);
      Set_Etype           (Id, Standard_Void_Type);
      Set_Enclosing_Scope (Id, Current_Scope);
   end Analyze_Implicit_Label_Declaration;
 
   ------------------------------
   -- Analyze_Iteration_Scheme --
   ------------------------------
 
   procedure Analyze_Iteration_Scheme (N : Node_Id) is
 
      procedure Process_Bounds (R : Node_Id);
      --  If the iteration is given by a range, create temporaries and
      --  assignment statements block to capture the bounds and perform
      --  required finalization actions in case a bound includes a function
      --  call that uses the temporary stack. We first pre-analyze a copy of
      --  the range in order to determine the expected type, and analyze and
      --  resolve the original bounds.
 
      procedure Check_Controlled_Array_Attribute (DS : Node_Id);
      --  If the bounds are given by a 'Range reference on a function call
      --  that returns a controlled array, introduce an explicit declaration
      --  to capture the bounds, so that the function result can be finalized
      --  in timely fashion.
 
      function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean;
      --  N is the node for an arbitrary construct. This function searches the
      --  construct N to see if any expressions within it contain function
      --  calls that use the secondary stack, returning True if any such call
      --  is found, and False otherwise.
 
      --------------------
      -- Process_Bounds --
      --------------------
 
      procedure Process_Bounds (R : Node_Id) is
         Loc          : constant Source_Ptr := Sloc (N);
         R_Copy       : constant Node_Id := New_Copy_Tree (R);
         Lo           : constant Node_Id := Low_Bound  (R);
         Hi           : constant Node_Id := High_Bound (R);
         New_Lo_Bound : Node_Id;
         New_Hi_Bound : Node_Id;
         Typ          : Entity_Id;
 
         function One_Bound
           (Original_Bound : Node_Id;
            Analyzed_Bound : Node_Id) return Node_Id;
         --  Capture value of bound and return captured value
 
         ---------------
         -- One_Bound --
         ---------------
 
         function One_Bound
           (Original_Bound : Node_Id;
            Analyzed_Bound : Node_Id) return Node_Id
         is
            Assign : Node_Id;
            Id     : Entity_Id;
            Decl   : Node_Id;
 
         begin
            --  If the bound is a constant or an object, no need for a separate
            --  declaration. If the bound is the result of previous expansion
            --  it is already analyzed and should not be modified. Note that
            --  the Bound will be resolved later, if needed, as part of the
            --  call to Make_Index (literal bounds may need to be resolved to
            --  type Integer).
 
            if Analyzed (Original_Bound) then
               return Original_Bound;
 
            elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
                                            N_Character_Literal)
              or else Is_Entity_Name (Analyzed_Bound)
            then
               Analyze_And_Resolve (Original_Bound, Typ);
               return Original_Bound;
            end if;
 
            --  Here we need to capture the value
 
            Analyze_And_Resolve (Original_Bound, Typ);
 
            --  Normally, the best approach is simply to generate a constant
            --  declaration that captures the bound. However, there is a nasty
            --  case where this is wrong. If the bound is complex, and has a
            --  possible use of the secondary stack, we need to generate a
            --  separate assignment statement to ensure the creation of a block
            --  which will release the secondary stack.
 
            --  We prefer the constant declaration, since it leaves us with a
            --  proper trace of the value, useful in optimizations that get rid
            --  of junk range checks.
 
            if not Has_Call_Using_Secondary_Stack (Original_Bound) then
               Force_Evaluation (Original_Bound);
               return Original_Bound;
            end if;
 
            Id := Make_Temporary (Loc, 'R', Original_Bound);
 
            --  Here we make a declaration with a separate assignment
            --  statement, and insert before loop header.
 
            Decl :=
              Make_Object_Declaration (Loc,
                Defining_Identifier => Id,
                Object_Definition   => New_Occurrence_Of (Typ, Loc));
 
            Assign :=
              Make_Assignment_Statement (Loc,
                Name        => New_Occurrence_Of (Id, Loc),
                Expression  => Relocate_Node (Original_Bound));
 
            --  We must recursively clean in the relocated expression the flag
            --  analyzed to ensure that the expression is reanalyzed. Required
            --  to ensure that the transient scope is established now (because
            --  Establish_Transient_Scope discarded generating transient scopes
            --  in the analysis of the iteration scheme).
 
            Reset_Analyzed_Flags (Expression (Assign));
 
            Insert_Actions (Parent (N), New_List (Decl, Assign));
 
            --  Now that this temporary variable is initialized we decorate it
            --  as safe-to-reevaluate to inform to the backend that no further
            --  asignment will be issued and hence it can be handled as side
            --  effect free. Note that this decoration must be done when the
            --  assignment has been analyzed because otherwise it will be
            --  rejected (see Analyze_Assignment).
 
            Set_Is_Safe_To_Reevaluate (Id);
 
            Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
 
            if Nkind (Assign) = N_Assignment_Statement then
               return Expression (Assign);
            else
               return Original_Bound;
            end if;
         end One_Bound;
 
      --  Start of processing for Process_Bounds
 
      begin
         Set_Parent (R_Copy, Parent (R));
         Pre_Analyze_Range (R_Copy);
         Typ := Etype (R_Copy);
 
         --  If the type of the discrete range is Universal_Integer, then the
         --  bound's type must be resolved to Integer, and any object used to
         --  hold the bound must also have type Integer, unless the literal
         --  bounds are constant-folded expressions with a user-defined type.
 
         if Typ = Universal_Integer then
            if Nkind (Lo) = N_Integer_Literal
              and then Present (Etype (Lo))
              and then Scope (Etype (Lo)) /= Standard_Standard
            then
               Typ := Etype (Lo);
 
            elsif Nkind (Hi) = N_Integer_Literal
              and then Present (Etype (Hi))
              and then Scope (Etype (Hi)) /= Standard_Standard
            then
               Typ := Etype (Hi);
 
            else
               Typ := Standard_Integer;
            end if;
         end if;
 
         Set_Etype (R, Typ);
 
         New_Lo_Bound := One_Bound (Lo, Low_Bound  (R_Copy));
         New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
 
         --  Propagate staticness to loop range itself, in case the
         --  corresponding subtype is static.
 
         if New_Lo_Bound /= Lo
           and then Is_Static_Expression (New_Lo_Bound)
         then
            Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
         end if;
 
         if New_Hi_Bound /= Hi
           and then Is_Static_Expression (New_Hi_Bound)
         then
            Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
         end if;
      end Process_Bounds;
 
      --------------------------------------
      -- Check_Controlled_Array_Attribute --
      --------------------------------------
 
      procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
      begin
         if Nkind (DS) = N_Attribute_Reference
            and then Is_Entity_Name (Prefix (DS))
            and then Ekind (Entity (Prefix (DS))) = E_Function
            and then Is_Array_Type (Etype (Entity (Prefix (DS))))
            and then
              Is_Controlled (
                Component_Type (Etype (Entity (Prefix (DS)))))
            and then Expander_Active
         then
            declare
               Loc  : constant Source_Ptr := Sloc (N);
               Arr  : constant Entity_Id := Etype (Entity (Prefix (DS)));
               Indx : constant Entity_Id :=
                        Base_Type (Etype (First_Index (Arr)));
               Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
               Decl : Node_Id;
 
            begin
               Decl :=
                 Make_Subtype_Declaration (Loc,
                   Defining_Identifier => Subt,
                   Subtype_Indication  =>
                      Make_Subtype_Indication (Loc,
                        Subtype_Mark  => New_Reference_To (Indx, Loc),
                        Constraint =>
                          Make_Range_Constraint (Loc,
                            Relocate_Node (DS))));
               Insert_Before (Parent (N), Decl);
               Analyze (Decl);
 
               Rewrite (DS,
                  Make_Attribute_Reference (Loc,
                    Prefix => New_Reference_To (Subt, Loc),
                    Attribute_Name => Attribute_Name (DS)));
               Analyze (DS);
            end;
         end if;
      end Check_Controlled_Array_Attribute;
 
      ------------------------------------
      -- Has_Call_Using_Secondary_Stack --
      ------------------------------------
 
      function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean is
 
         function Check_Call (N : Node_Id) return Traverse_Result;
         --  Check if N is a function call which uses the secondary stack
 
         ----------------
         -- Check_Call --
         ----------------
 
         function Check_Call (N : Node_Id) return Traverse_Result is
            Nam        : Node_Id;
            Subp       : Entity_Id;
            Return_Typ : Entity_Id;
 
         begin
            if Nkind (N) = N_Function_Call then
               Nam := Name (N);
 
               --  Call using access to subprogram with explicit dereference
 
               if Nkind (Nam) = N_Explicit_Dereference then
                  Subp := Etype (Nam);
 
               --  Normal case
 
               else
                  Subp := Entity (Nam);
               end if;
 
               Return_Typ := Etype (Subp);
 
               if Is_Composite_Type (Return_Typ)
                 and then not Is_Constrained (Return_Typ)
               then
                  return Abandon;
 
               elsif Sec_Stack_Needed_For_Return (Subp) then
                  return Abandon;
               end if;
            end if;
 
            --  Continue traversing the tree
 
            return OK;
         end Check_Call;
 
         function Check_Calls is new Traverse_Func (Check_Call);
 
      --  Start of processing for Has_Call_Using_Secondary_Stack
 
      begin
         return Check_Calls (N) = Abandon;
      end Has_Call_Using_Secondary_Stack;
 
   --  Start of processing for Analyze_Iteration_Scheme
 
   begin
      --  If this is a rewritten quantified expression, the iteration scheme
      --  has been analyzed already. Do no repeat analysis because the loop
      --  variable is already declared.
 
      if Analyzed (N) then
         return;
      end if;
 
      --  For an infinite loop, there is no iteration scheme
 
      if No (N) then
         return;
      end if;
 
      --  Iteration scheme is present
 
      declare
         Cond : constant Node_Id := Condition (N);
 
      begin
         --  For WHILE loop, verify that the condition is a Boolean expression
         --  and resolve and check it.
 
         if Present (Cond) then
            Analyze_And_Resolve (Cond, Any_Boolean);
            Check_Unset_Reference (Cond);
            Set_Current_Value_Condition (N);
            return;
 
         --  For an iterator specification with "of", pre-analyze range to
         --  capture function calls that may require finalization actions.
 
         elsif Present (Iterator_Specification (N)) then
            Pre_Analyze_Range (Name (Iterator_Specification (N)));
            Analyze_Iterator_Specification (Iterator_Specification (N));
 
         --  Else we have a FOR loop
 
         else
            declare
               LP : constant Node_Id   := Loop_Parameter_Specification (N);
               Id : constant Entity_Id := Defining_Identifier (LP);
               DS : constant Node_Id   := Discrete_Subtype_Definition (LP);
 
               D_Copy : Node_Id;
 
            begin
               Enter_Name (Id);
 
               --  We always consider the loop variable to be referenced, since
               --  the loop may be used just for counting purposes.
 
               Generate_Reference (Id, N, ' ');
 
               --  Check for the case of loop variable hiding a local variable
               --  (used later on to give a nice warning if the hidden variable
               --  is never assigned).
 
               declare
                  H : constant Entity_Id := Homonym (Id);
               begin
                  if Present (H)
                    and then Enclosing_Dynamic_Scope (H) =
                               Enclosing_Dynamic_Scope (Id)
                    and then Ekind (H) = E_Variable
                    and then Is_Discrete_Type (Etype (H))
                  then
                     Set_Hiding_Loop_Variable (H, Id);
                  end if;
               end;
 
               --  Loop parameter specification must include subtype mark in
               --  SPARK.
 
               if Nkind (DS) = N_Range then
                  Check_SPARK_Restriction
                    ("loop parameter specification must include subtype mark",
                     N);
               end if;
 
               --  Now analyze the subtype definition. If it is a range, create
               --  temporaries for bounds.
 
               if Nkind (DS) = N_Range
                 and then Expander_Active
               then
                  Process_Bounds (DS);
 
               --  Expander not active or else range of iteration is a subtype
               --  indication, an entity, or a function call that yields an
               --  aggregate or a container.
 
               else
                  D_Copy := New_Copy_Tree (DS);
                  Set_Parent (D_Copy, Parent (DS));
                  Pre_Analyze_Range (D_Copy);
 
                  --  Ada 2012: If the domain of iteration is a function call,
                  --  it is the new iterator form.
 
                  --  We have also implemented the shorter form : for X in S
                  --  for Alfa use. In this case, 'Old and 'Result must be
                  --  treated as entity names over which iterators are legal.
 
                  if Nkind (D_Copy) = N_Function_Call
                    or else
                      (Alfa_Mode
                        and then (Nkind (D_Copy) = N_Attribute_Reference
                        and then
                          (Attribute_Name (D_Copy) = Name_Result
                            or else Attribute_Name (D_Copy) = Name_Old)))
                    or else
                      (Is_Entity_Name (D_Copy)
                        and then not Is_Type (Entity (D_Copy)))
                  then
                     --  This is an iterator specification. Rewrite as such
                     --  and analyze, to capture function calls that may
                     --  require finalization actions.
 
                     declare
                        I_Spec : constant Node_Id :=
                                   Make_Iterator_Specification (Sloc (LP),
                                     Defining_Identifier =>
                                       Relocate_Node (Id),
                                     Name                => D_Copy,
                                     Subtype_Indication  => Empty,
                                     Reverse_Present     =>
                                       Reverse_Present (LP));
                     begin
                        Set_Iterator_Specification (N, I_Spec);
                        Set_Loop_Parameter_Specification (N, Empty);
                        Analyze_Iterator_Specification (I_Spec);
 
                        --  In a generic context, analyze the original domain
                        --  of iteration, for name capture.
 
                        if not Expander_Active then
                           Analyze (DS);
                        end if;
 
                        --  Set kind of loop parameter, which may be used in
                        --  the subsequent analysis of the condition in a
                        --  quantified expression.
 
                        Set_Ekind (Id, E_Loop_Parameter);
                        return;
                     end;
 
                  --  Domain of iteration is not a function call, and is
                  --  side-effect free.
 
                  else
                     Analyze (DS);
                  end if;
               end if;
 
               if DS = Error then
                  return;
               end if;
 
               --  Some additional checks if we are iterating through a type
 
               if Is_Entity_Name (DS)
                 and then Present (Entity (DS))
                 and then Is_Type (Entity (DS))
               then
                  --  The subtype indication may denote the completion of an
                  --  incomplete type declaration.
 
                  if Ekind (Entity (DS)) = E_Incomplete_Type then
                     Set_Entity (DS, Get_Full_View (Entity (DS)));
                     Set_Etype  (DS, Entity (DS));
                  end if;
 
                  --  Attempt to iterate through non-static predicate
 
                  if Is_Discrete_Type (Entity (DS))
                    and then Present (Predicate_Function (Entity (DS)))
                    and then No (Static_Predicate (Entity (DS)))
                  then
                     Bad_Predicated_Subtype_Use
                       ("cannot use subtype& with non-static "
                        & "predicate for loop iteration", DS, Entity (DS));
                  end if;
               end if;
 
               --  Error if not discrete type
 
               if not Is_Discrete_Type (Etype (DS)) then
                  Wrong_Type (DS, Any_Discrete);
                  Set_Etype (DS, Any_Type);
               end if;
 
               Check_Controlled_Array_Attribute (DS);
 
               Make_Index (DS, LP, In_Iter_Schm => True);
 
               Set_Ekind (Id, E_Loop_Parameter);
 
               --  If the loop is part of a predicate or precondition, it may
               --  be analyzed twice, once in the source and once on the copy
               --  used to check conformance. Preserve the original itype
               --  because the second one may be created in a different scope,
               --  e.g. a precondition procedure, leading to a crash in GIGI.
 
               if No (Etype (Id)) or else Etype (Id) = Any_Type then
                  Set_Etype (Id, Etype (DS));
               end if;
 
               --  Treat a range as an implicit reference to the type, to
               --  inhibit spurious warnings.
 
               Generate_Reference (Base_Type (Etype (DS)), N, ' ');
               Set_Is_Known_Valid (Id, True);
 
               --  The loop is not a declarative part, so the only entity
               --  declared "within" must be frozen explicitly.
 
               declare
                  Flist : constant List_Id := Freeze_Entity (Id, N);
               begin
                  if Is_Non_Empty_List (Flist) then
                     Insert_Actions (N, Flist);
                  end if;
               end;
 
               --  Check for null or possibly null range and issue warning. We
               --  suppress such messages in generic templates and instances,
               --  because in practice they tend to be dubious in these cases.
 
               if Nkind (DS) = N_Range and then Comes_From_Source (N) then
                  declare
                     L : constant Node_Id := Low_Bound  (DS);
                     H : constant Node_Id := High_Bound (DS);
 
                  begin
                     --  If range of loop is null, issue warning
 
                     if Compile_Time_Compare
                          (L, H, Assume_Valid => True) = GT
                     then
                        --  Suppress the warning if inside a generic template
                        --  or instance, since in practice they tend to be
                        --  dubious in these cases since they can result from
                        --  intended parametrization.
 
                        if not Inside_A_Generic
                          and then not In_Instance
                        then
                           --  Specialize msg if invalid values could make the
                           --  loop non-null after all.
 
                           if Compile_Time_Compare
                                (L, H, Assume_Valid => False) = GT
                           then
                              Error_Msg_N
                                ("?loop range is null, loop will not execute",
                                 DS);
 
                              --  Since we know the range of the loop is null,
                              --  set the appropriate flag to remove the loop
                              --  entirely during expansion.
 
                              Set_Is_Null_Loop (Parent (N));
 
                              --  Here is where the loop could execute because
                              --  of invalid values, so issue appropriate
                              --  message and in this case we do not set the
                              --  Is_Null_Loop flag since the loop may execute.
 
                           else
                              Error_Msg_N
                                ("?loop range may be null, "
                                 & "loop may not execute",
                                 DS);
                              Error_Msg_N
                                ("?can only execute if invalid values "
                                 & "are present",
                                 DS);
                           end if;
                        end if;
 
                        --  In either case, suppress warnings in the body of
                        --  the loop, since it is likely that these warnings
                        --  will be inappropriate if the loop never actually
                        --  executes, which is likely.
 
                        Set_Suppress_Loop_Warnings (Parent (N));
 
                        --  The other case for a warning is a reverse loop
                        --  where the upper bound is the integer literal zero
                        --  or one, and the lower bound can be positive.
 
                        --  For example, we have
 
                        --     for J in reverse N .. 1 loop
 
                        --  In practice, this is very likely to be a case of
                        --  reversing the bounds incorrectly in the range.
 
                     elsif Reverse_Present (LP)
                       and then Nkind (Original_Node (H)) =
                                                      N_Integer_Literal
                       and then (Intval (Original_Node (H)) = Uint_0
                                  or else
                                    Intval (Original_Node (H)) = Uint_1)
                     then
                        Error_Msg_N ("?loop range may be null", DS);
                        Error_Msg_N ("\?bounds may be wrong way round", DS);
                     end if;
                  end;
               end if;
            end;
         end if;
      end;
   end Analyze_Iteration_Scheme;
 
   -------------------------------------
   --  Analyze_Iterator_Specification --
   -------------------------------------
 
   procedure Analyze_Iterator_Specification (N : Node_Id) is
      Loc       : constant Source_Ptr := Sloc (N);
      Def_Id    : constant Node_Id    := Defining_Identifier (N);
      Subt      : constant Node_Id    := Subtype_Indication (N);
      Iter_Name : constant Node_Id    := Name (N);
 
      Ent : Entity_Id;
      Typ : Entity_Id;
 
   begin
      --  In semantics/Alfa modes, we won't be further expanding the loop, so
      --  introduce loop variable so that loop body can be properly analyzed.
      --  Otherwise this happens after expansion.
 
      if Operating_Mode = Check_Semantics
        or else Alfa_Mode
      then
         Enter_Name (Def_Id);
      end if;
 
      Set_Ekind (Def_Id, E_Variable);
 
      if Present (Subt) then
         Analyze (Subt);
      end if;
 
      --  If domain of iteration is an expression, create a declaration for
      --  it, so that finalization actions are introduced outside of the loop.
      --  The declaration must be a renaming because the body of the loop may
      --  assign to elements.
 
      if not Is_Entity_Name (Iter_Name) then
         declare
            Id   : constant Entity_Id := Make_Temporary (Loc, 'R', Iter_Name);
            Decl : Node_Id;
 
         begin
            Typ := Etype (Iter_Name);
 
            --  The name in the renaming declaration may be a function call.
            --  Indicate that it does not come from source, to suppress
            --  spurious warnings on renamings of parameterless functions,
            --  a common enough idiom in user-defined iterators.
 
            Decl :=
              Make_Object_Renaming_Declaration (Loc,
                Defining_Identifier => Id,
                Subtype_Mark        => New_Occurrence_Of (Typ, Loc),
                Name                =>
                  New_Copy_Tree (Iter_Name, New_Sloc => Loc));
 
            Insert_Actions (Parent (Parent (N)), New_List (Decl));
            Rewrite (Name (N), New_Occurrence_Of (Id, Loc));
            Set_Etype (Id, Typ);
            Set_Etype (Name (N), Typ);
         end;
 
      --  Container is an entity or an array with uncontrolled components, or
      --  else it is a container iterator given by a function call, typically
      --  called Iterate in the case of predefined containers, even though
      --  Iterate is not a reserved name. What matter is that the return type
      --  of the function is an iterator type.
 
      else
         Analyze (Iter_Name);
 
         if Nkind (Iter_Name) = N_Function_Call then
            declare
               C  : constant Node_Id := Name (Iter_Name);
               I  : Interp_Index;
               It : Interp;
 
            begin
               if not Is_Overloaded (Iter_Name) then
                  Resolve (Iter_Name, Etype (C));
 
               else
                  Get_First_Interp (C, I, It);
                  while It.Typ /= Empty loop
                     if Reverse_Present (N) then
                        if Is_Reversible_Iterator (It.Typ) then
                           Resolve (Iter_Name, It.Typ);
                           exit;
                        end if;
 
                     elsif Is_Iterator (It.Typ) then
                        Resolve (Iter_Name, It.Typ);
                        exit;
                     end if;
 
                     Get_Next_Interp (I, It);
                  end loop;
               end if;
            end;
 
         --  Domain of iteration is not overloaded
 
         else
            Resolve (Iter_Name, Etype (Iter_Name));
         end if;
      end if;
 
      Typ := Etype (Iter_Name);
 
      if Is_Array_Type (Typ) then
         if Of_Present (N) then
            Set_Etype (Def_Id, Component_Type (Typ));
 
         --  Here we have a missing Range attribute
 
         else
            Error_Msg_N
              ("missing Range attribute in iteration over an array", N);
 
            --  In Ada 2012 mode, this may be an attempt at an iterator
 
            if Ada_Version >= Ada_2012 then
               Error_Msg_NE
                 ("\if& is meant to designate an element of the array, use OF",
                    N, Def_Id);
            end if;
 
            --  Prevent cascaded errors
 
            Set_Ekind (Def_Id, E_Loop_Parameter);
            Set_Etype (Def_Id, Etype (First_Index (Typ)));
         end if;
 
         --  Check for type error in iterator
 
      elsif Typ = Any_Type then
         return;
 
      --  Iteration over a container
 
      else
         Set_Ekind (Def_Id, E_Loop_Parameter);
 
         if Of_Present (N) then
 
            --  The type of the loop variable is the Iterator_Element aspect of
            --  the container type.
 
            declare
               Element : constant Entity_Id :=
                           Find_Aspect (Typ, Aspect_Iterator_Element);
            begin
               if No (Element) then
                  Error_Msg_NE ("cannot iterate over&", N, Typ);
                  return;
               else
                  Set_Etype (Def_Id, Entity (Element));
               end if;
            end;
 
         else
            --  For an iteration of the form IN, the name must denote an
            --  iterator, typically the result of a call to Iterate. Give a
            --  useful error message when the name is a container by itself.
 
            if Is_Entity_Name (Original_Node (Name (N)))
              and then not Is_Iterator (Typ)
            then
               if No (Find_Aspect (Typ, Aspect_Iterator_Element)) then
                  Error_Msg_NE
                    ("cannot iterate over&", Name (N), Typ);
               else
                  Error_Msg_N
                    ("name must be an iterator, not a container", Name (N));
               end if;
 
               Error_Msg_NE
                 ("\to iterate directly over the elements of a container, " &
                   "write `of &`", Name (N), Original_Node (Name (N)));
            end if;
 
            --  The result type of Iterate function is the classwide type of
            --  the interface parent. We need the specific Cursor type defined
            --  in the container package.
 
            Ent := First_Entity (Scope (Typ));
            while Present (Ent) loop
               if Chars (Ent) = Name_Cursor then
                  Set_Etype (Def_Id, Etype (Ent));
                  exit;
               end if;
 
               Next_Entity (Ent);
            end loop;
         end if;
      end if;
   end Analyze_Iterator_Specification;
 
   -------------------
   -- Analyze_Label --
   -------------------
 
   --  Note: the semantic work required for analyzing labels (setting them as
   --  reachable) was done in a prepass through the statements in the block,
   --  so that forward gotos would be properly handled. See Analyze_Statements
   --  for further details. The only processing required here is to deal with
   --  optimizations that depend on an assumption of sequential control flow,
   --  since of course the occurrence of a label breaks this assumption.
 
   procedure Analyze_Label (N : Node_Id) is
      pragma Warnings (Off, N);
   begin
      Kill_Current_Values;
   end Analyze_Label;
 
   --------------------------
   -- Analyze_Label_Entity --
   --------------------------
 
   procedure Analyze_Label_Entity (E : Entity_Id) is
   begin
      Set_Ekind           (E, E_Label);
      Set_Etype           (E, Standard_Void_Type);
      Set_Enclosing_Scope (E, Current_Scope);
      Set_Reachable       (E, True);
   end Analyze_Label_Entity;
 
   ----------------------------
   -- Analyze_Loop_Statement --
   ----------------------------
 
   procedure Analyze_Loop_Statement (N : Node_Id) is
 
      function Is_Container_Iterator (Iter : Node_Id) return Boolean;
      --  Given a loop iteration scheme, determine whether it is an Ada 2012
      --  container iteration.
 
      function Is_Wrapped_In_Block (N : Node_Id) return Boolean;
      --  Determine whether node N is the sole statement of a block
 
      ---------------------------
      -- Is_Container_Iterator --
      ---------------------------
 
      function Is_Container_Iterator (Iter : Node_Id) return Boolean is
      begin
         --  Infinite loop
 
         if No (Iter) then
            return False;
 
         --  While loop
 
         elsif Present (Condition (Iter)) then
            return False;
 
         --  for Def_Id in [reverse] Name loop
         --  for Def_Id [: Subtype_Indication] of [reverse] Name loop
 
         elsif Present (Iterator_Specification (Iter)) then
            declare
               Nam : constant Node_Id := Name (Iterator_Specification (Iter));
               Nam_Copy : Node_Id;
 
            begin
               Nam_Copy := New_Copy_Tree (Nam);
               Set_Parent (Nam_Copy, Parent (Nam));
               Pre_Analyze_Range (Nam_Copy);
 
               --  The only two options here are iteration over a container or
               --  an array.
 
               return not Is_Array_Type (Etype (Nam_Copy));
            end;
 
         --  for Def_Id in [reverse] Discrete_Subtype_Definition loop
 
         else
            declare
               LP : constant Node_Id := Loop_Parameter_Specification (Iter);
               DS : constant Node_Id := Discrete_Subtype_Definition (LP);
               DS_Copy : Node_Id;
 
            begin
               DS_Copy := New_Copy_Tree (DS);
               Set_Parent (DS_Copy, Parent (DS));
               Pre_Analyze_Range (DS_Copy);
 
               --  Check for a call to Iterate ()
 
               return
                 Nkind (DS_Copy) = N_Function_Call
                   and then Needs_Finalization (Etype (DS_Copy));
            end;
         end if;
      end Is_Container_Iterator;
 
      -------------------------
      -- Is_Wrapped_In_Block --
      -------------------------
 
      function Is_Wrapped_In_Block (N : Node_Id) return Boolean is
         HSS : constant Node_Id := Parent (N);
 
      begin
         return
           Nkind (HSS) = N_Handled_Sequence_Of_Statements
             and then Nkind (Parent (HSS)) = N_Block_Statement
             and then First (Statements (HSS)) = N
             and then No (Next (First (Statements (HSS))));
      end Is_Wrapped_In_Block;
 
      --  Local declarations
 
      Id   : constant Node_Id := Identifier (N);
      Iter : constant Node_Id := Iteration_Scheme (N);
      Loc  : constant Source_Ptr := Sloc (N);
      Ent  : Entity_Id;
 
   --  Start of processing for Analyze_Loop_Statement
 
   begin
      if Present (Id) then
 
         --  Make name visible, e.g. for use in exit statements. Loop labels
         --  are always considered to be referenced.
 
         Analyze (Id);
         Ent := Entity (Id);
 
         --  Guard against serious error (typically, a scope mismatch when
         --  semantic analysis is requested) by creating loop entity to
         --  continue analysis.
 
         if No (Ent) then
            if Total_Errors_Detected /= 0 then
               Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L');
            else
               raise Program_Error;
            end if;
 
         else
            Generate_Reference (Ent, N, ' ');
            Generate_Definition (Ent);
 
            --  If we found a label, mark its type. If not, ignore it, since it
            --  means we have a conflicting declaration, which would already
            --  have been diagnosed at declaration time. Set Label_Construct
            --  of the implicit label declaration, which is not created by the
            --  parser for generic units.
 
            if Ekind (Ent) = E_Label then
               Set_Ekind (Ent, E_Loop);
 
               if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
                  Set_Label_Construct (Parent (Ent), N);
               end if;
            end if;
         end if;
 
      --  Case of no identifier present
 
      else
         Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L');
         Set_Etype  (Ent, Standard_Void_Type);
         Set_Parent (Ent, N);
      end if;
 
      --  Iteration over a container in Ada 2012 involves the creation of a
      --  controlled iterator object. Wrap the loop in a block to ensure the
      --  timely finalization of the iterator and release of container locks.
 
      if Ada_Version >= Ada_2012
        and then Is_Container_Iterator (Iter)
        and then not Is_Wrapped_In_Block (N)
      then
         Rewrite (N,
           Make_Block_Statement (Loc,
             Declarations               => New_List,
             Handled_Statement_Sequence =>
               Make_Handled_Sequence_Of_Statements (Loc,
                 Statements => New_List (Relocate_Node (N)))));
 
         Analyze (N);
         return;
      end if;
 
      --  Kill current values on entry to loop, since statements in the body of
      --  the loop may have been executed before the loop is entered. Similarly
      --  we kill values after the loop, since we do not know that the body of
      --  the loop was executed.
 
      Kill_Current_Values;
      Push_Scope (Ent);
      Analyze_Iteration_Scheme (Iter);
 
      --  Analyze the statements of the body except in the case of an Ada 2012
      --  iterator with the expander active. In this case the expander will do
      --  a rewrite of the loop into a while loop. We will then analyze the
      --  loop body when we analyze this while loop.
 
      --  We need to do this delay because if the container is for indefinite
      --  types the actual subtype of the components will only be determined
      --  when the cursor declaration is analyzed.
 
      --  If the expander is not active, then we want to analyze the loop body
      --  now even in the Ada 2012 iterator case, since the rewriting will not
      --  be done. Insert the loop variable in the current scope, if not done
      --  when analysing the iteration scheme.
 
      if No (Iter)
        or else No (Iterator_Specification (Iter))
        or else not Expander_Active
      then
         if Present (Iter)
           and then Present (Iterator_Specification (Iter))
         then
            declare
               Id : constant Entity_Id :=
                      Defining_Identifier (Iterator_Specification (Iter));
            begin
               if Scope (Id) /= Current_Scope then
                  Enter_Name (Id);
               end if;
            end;
         end if;
 
         Analyze_Statements (Statements (N));
      end if;
 
      --  Finish up processing for the loop. We kill all current values, since
      --  in general we don't know if the statements in the loop have been
      --  executed. We could do a bit better than this with a loop that we
      --  know will execute at least once, but it's not worth the trouble and
      --  the front end is not in the business of flow tracing.
 
      Process_End_Label (N, 'e', Ent);
      End_Scope;
      Kill_Current_Values;
 
      --  Check for infinite loop. Skip check for generated code, since it
      --  justs waste time and makes debugging the routine called harder.
 
      --  Note that we have to wait till the body of the loop is fully analyzed
      --  before making this call, since Check_Infinite_Loop_Warning relies on
      --  being able to use semantic visibility information to find references.
 
      if Comes_From_Source (N) then
         Check_Infinite_Loop_Warning (N);
      end if;
 
      --  Code after loop is unreachable if the loop has no WHILE or FOR and
      --  contains no EXIT statements within the body of the loop.
 
      if No (Iter) and then not Has_Exit (Ent) then
         Check_Unreachable_Code (N);
      end if;
   end Analyze_Loop_Statement;
 
   ----------------------------
   -- Analyze_Null_Statement --
   ----------------------------
 
   --  Note: the semantics of the null statement is implemented by a single
   --  null statement, too bad everything isn't as simple as this!
 
   procedure Analyze_Null_Statement (N : Node_Id) is
      pragma Warnings (Off, N);
   begin
      null;
   end Analyze_Null_Statement;
 
   ------------------------
   -- Analyze_Statements --
   ------------------------
 
   procedure Analyze_Statements (L : List_Id) is
      S   : Node_Id;
      Lab : Entity_Id;
 
   begin
      --  The labels declared in the statement list are reachable from
      --  statements in the list. We do this as a prepass so that any goto
      --  statement will be properly flagged if its target is not reachable.
      --  This is not required, but is nice behavior!
 
      S := First (L);
      while Present (S) loop
         if Nkind (S) = N_Label then
            Analyze (Identifier (S));
            Lab := Entity (Identifier (S));
 
            --  If we found a label mark it as reachable
 
            if Ekind (Lab) = E_Label then
               Generate_Definition (Lab);
               Set_Reachable (Lab);
 
               if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
                  Set_Label_Construct (Parent (Lab), S);
               end if;
 
            --  If we failed to find a label, it means the implicit declaration
            --  of the label was hidden.  A for-loop parameter can do this to
            --  a label with the same name inside the loop, since the implicit
            --  label declaration is in the innermost enclosing body or block
            --  statement.
 
            else
               Error_Msg_Sloc := Sloc (Lab);
               Error_Msg_N
                 ("implicit label declaration for & is hidden#",
                  Identifier (S));
            end if;
         end if;
 
         Next (S);
      end loop;
 
      --  Perform semantic analysis on all statements
 
      Conditional_Statements_Begin;
 
      S := First (L);
      while Present (S) loop
         Analyze (S);
 
         --  Remove dimension in all statements
 
         Remove_Dimension_In_Statement (S);
         Next (S);
      end loop;
 
      Conditional_Statements_End;
 
      --  Make labels unreachable. Visibility is not sufficient, because labels
      --  in one if-branch for example are not reachable from the other branch,
      --  even though their declarations are in the enclosing declarative part.
 
      S := First (L);
      while Present (S) loop
         if Nkind (S) = N_Label then
            Set_Reachable (Entity (Identifier (S)), False);
         end if;
 
         Next (S);
      end loop;
   end Analyze_Statements;
 
   ----------------------------
   -- Check_Unreachable_Code --
   ----------------------------
 
   procedure Check_Unreachable_Code (N : Node_Id) is
      Error_Node : Node_Id;
      P          : Node_Id;
 
   begin
      if Is_List_Member (N)
        and then Comes_From_Source (N)
      then
         declare
            Nxt : Node_Id;
 
         begin
            Nxt := Original_Node (Next (N));
 
            --  If a label follows us, then we never have dead code, since
            --  someone could branch to the label, so we just ignore it, unless
            --  we are in formal mode where goto statements are not allowed.
 
            if Nkind (Nxt) = N_Label
              and then not Restriction_Check_Required (SPARK)
            then
               return;
 
            --  Otherwise see if we have a real statement following us
 
            elsif Present (Nxt)
              and then Comes_From_Source (Nxt)
              and then Is_Statement (Nxt)
            then
               --  Special very annoying exception. If we have a return that
               --  follows a raise, then we allow it without a warning, since
               --  the Ada RM annoyingly requires a useless return here!
 
               if Nkind (Original_Node (N)) /= N_Raise_Statement
                 or else Nkind (Nxt) /= N_Simple_Return_Statement
               then
                  --  The rather strange shenanigans with the warning message
                  --  here reflects the fact that Kill_Dead_Code is very good
                  --  at removing warnings in deleted code, and this is one
                  --  warning we would prefer NOT to have removed.
 
                  Error_Node := Nxt;
 
                  --  If we have unreachable code, analyze and remove the
                  --  unreachable code, since it is useless and we don't
                  --  want to generate junk warnings.
 
                  --  We skip this step if we are not in code generation mode.
                  --  This is the one case where we remove dead code in the
                  --  semantics as opposed to the expander, and we do not want
                  --  to remove code if we are not in code generation mode,
                  --  since this messes up the ASIS trees.
 
                  --  Note that one might react by moving the whole circuit to
                  --  exp_ch5, but then we lose the warning in -gnatc mode.
 
                  if Operating_Mode = Generate_Code then
                     loop
                        Nxt := Next (N);
 
                        --  Quit deleting when we have nothing more to delete
                        --  or if we hit a label (since someone could transfer
                        --  control to a label, so we should not delete it).
 
                        exit when No (Nxt) or else Nkind (Nxt) = N_Label;
 
                        --  Statement/declaration is to be deleted
 
                        Analyze (Nxt);
                        Remove (Nxt);
                        Kill_Dead_Code (Nxt);
                     end loop;
                  end if;
 
                  --  Now issue the warning (or error in formal mode)
 
                  if Restriction_Check_Required (SPARK) then
                     Check_SPARK_Restriction
                       ("unreachable code is not allowed", Error_Node);
                  else
                     Error_Msg ("?unreachable code!", Sloc (Error_Node));
                  end if;
               end if;
 
            --  If the unconditional transfer of control instruction is the
            --  last statement of a sequence, then see if our parent is one of
            --  the constructs for which we count unblocked exits, and if so,
            --  adjust the count.
 
            else
               P := Parent (N);
 
               --  Statements in THEN part or ELSE part of IF statement
 
               if Nkind (P) = N_If_Statement then
                  null;
 
               --  Statements in ELSIF part of an IF statement
 
               elsif Nkind (P) = N_Elsif_Part then
                  P := Parent (P);
                  pragma Assert (Nkind (P) = N_If_Statement);
 
               --  Statements in CASE statement alternative
 
               elsif Nkind (P) = N_Case_Statement_Alternative then
                  P := Parent (P);
                  pragma Assert (Nkind (P) = N_Case_Statement);
 
               --  Statements in body of block
 
               elsif Nkind (P) = N_Handled_Sequence_Of_Statements
                 and then Nkind (Parent (P)) = N_Block_Statement
               then
                  null;
 
               --  Statements in exception handler in a block
 
               elsif Nkind (P) = N_Exception_Handler
                 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
                 and then Nkind (Parent (Parent (P))) = N_Block_Statement
               then
                  null;
 
               --  None of these cases, so return
 
               else
                  return;
               end if;
 
               --  This was one of the cases we are looking for (i.e. the
               --  parent construct was IF, CASE or block) so decrement count.
 
               Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
            end if;
         end;
      end if;
   end Check_Unreachable_Code;
 
   -----------------------
   -- Pre_Analyze_Range --
   -----------------------
 
   procedure Pre_Analyze_Range (R_Copy : Node_Id) is
      Save_Analysis : constant Boolean := Full_Analysis;
 
   begin
      Full_Analysis := False;
      Expander_Mode_Save_And_Set (False);
 
      Analyze (R_Copy);
 
      if Nkind (R_Copy) in N_Subexpr
        and then Is_Overloaded (R_Copy)
      then
         --  Apply preference rules for range of predefined integer types, or
         --  diagnose true ambiguity.
 
         declare
            I     : Interp_Index;
            It    : Interp;
            Found : Entity_Id := Empty;
 
         begin
            Get_First_Interp (R_Copy, I, It);
            while Present (It.Typ) loop
               if Is_Discrete_Type (It.Typ) then
                  if No (Found) then
                     Found := It.Typ;
                  else
                     if Scope (Found) = Standard_Standard then
                        null;
 
                     elsif Scope (It.Typ) = Standard_Standard then
                        Found := It.Typ;
 
                     else
                        --  Both of them are user-defined
 
                        Error_Msg_N
                          ("ambiguous bounds in range of iteration", R_Copy);
                        Error_Msg_N ("\possible interpretations:", R_Copy);
                        Error_Msg_NE ("\\} ", R_Copy, Found);
                        Error_Msg_NE ("\\} ", R_Copy, It.Typ);
                        exit;
                     end if;
                  end if;
               end if;
 
               Get_Next_Interp (I, It);
            end loop;
         end;
      end if;
 
      --  Subtype mark in iteration scheme
 
      if Is_Entity_Name (R_Copy)
        and then Is_Type (Entity (R_Copy))
      then
         null;
 
      --  Expression in range, or Ada 2012 iterator
 
      elsif Nkind (R_Copy) in N_Subexpr then
         Resolve (R_Copy);
      end if;
 
      Expander_Mode_Restore;
      Full_Analysis := Save_Analysis;
   end Pre_Analyze_Range;
 
end Sem_Ch5;
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Line No.	Rev	Author	Line
1	706	jeremybenn	`------------------------------------------------------------------------------`
2			`-- --`
3			`-- GNAT COMPILER COMPONENTS --`
4			`-- --`
5			`-- S E M _ C H 5 --`
6			`-- --`
7			`-- B o d y --`
8			`-- --`
9			`-- Copyright (C) 1992-2011, Free Software Foundation, Inc. --`
10			`-- --`
11			`-- GNAT is free software; you can redistribute it and/or modify it under --`
12			`-- terms of the GNU General Public License as published by the Free Soft- --`
13			`-- ware Foundation; either version 3, or (at your option) any later ver- --`
14			`-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --`
15			`-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --`
16			`-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --`
17			`-- for more details. You should have received a copy of the GNU General --`
18			`-- Public License distributed with GNAT; see file COPYING3. If not, go to --`
19			`-- http://www.gnu.org/licenses for a complete copy of the license. --`
20			`-- --`
21			`-- GNAT was originally developed by the GNAT team at New York University. --`
22			`-- Extensive contributions were provided by Ada Core Technologies Inc. --`
23			`-- --`
24			`------------------------------------------------------------------------------`
25
26			`with Aspects; use Aspects;`
27			`with Atree; use Atree;`
28			`with Checks; use Checks;`
29			`with Einfo; use Einfo;`
30			`with Errout; use Errout;`
31			`with Expander; use Expander;`
32			`with Exp_Ch6; use Exp_Ch6;`
33			`with Exp_Util; use Exp_Util;`
34			`with Freeze; use Freeze;`
35			`with Lib; use Lib;`
36			`with Lib.Xref; use Lib.Xref;`
37			`with Namet; use Namet;`
38			`with Nlists; use Nlists;`
39			`with Nmake; use Nmake;`
40			`with Opt; use Opt;`