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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                                  P A R                                   --

--                                                                          --

--                                 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 Casing;   use Casing;

with Debug;    use Debug;

with Elists;   use Elists;

with Errout;   use Errout;

with Fname;    use Fname;

with Lib;      use Lib;

with Namet;    use Namet;

with Namet.Sp; use Namet.Sp;

with Nlists;   use Nlists;

with Nmake;    use Nmake;

with Opt;      use Opt;

with Output;   use Output;

with Par_SCO;  use Par_SCO;

with Restrict; use Restrict;

with Scans;    use Scans;

with Scn;      use Scn;

with Sem_Util; use Sem_Util;

with Sinput;   use Sinput;

with Sinput.L; use Sinput.L;

with Sinfo;    use Sinfo;

with Snames;   use Snames;

with Style;

with Stylesw;  use Stylesw;

with Table;

with Tbuild;   use Tbuild;

---------

-- Par --

---------

function Par (Configuration_Pragmas : Boolean) return List_Id is

   Num_Library_Units : Natural := 0;

   --  Count number of units parsed (relevant only in syntax check only mode,

   --  since in semantics check mode only a single unit is permitted anyway)

   Save_Config_Switches : Config_Switches_Type;

   --  Variable used to save values of config switches while we parse the

   --  new unit, to be restored on exit for proper recursive behavior.

   Loop_Block_Count : Nat := 0;

   --  Counter used for constructing loop/block names (see the routine

   --  Par.Ch5.Get_Loop_Block_Name)

   --------------------

   -- Error Recovery --

   --------------------

   --  When an error is encountered, a call is made to one of the Error_Msg

   --  routines to record the error. If the syntax scan is not derailed by the

   --  error (e.g. a complaint that logical operators are inconsistent in an

   --  EXPRESSION), then control returns from the Error_Msg call, and the

   --  parse continues unimpeded.

   --  If on the other hand, the Error_Msg represents a situation from which

   --  the parser cannot recover locally, the exception Error_Resync is raised

   --  immediately after the call to Error_Msg. Handlers for Error_Resync

   --  are located at strategic points to resynchronize the parse. For example,

   --  when an error occurs in a statement, the handler skips to the next

   --  semicolon and continues the scan from there.

   --  Each parsing procedure contains a note with the heading "Error recovery"

   --  which shows if it can propagate the Error_Resync exception. In order

   --  not to propagate the exception, a procedure must either contain its own

   --  handler for this exception, or it must not call any other routines which

   --  propagate the exception.

   --  Note: the arrangement of Error_Resync handlers is such that it should

   --  never be possible to transfer control through a procedure which made

   --  an entry in the scope stack, invalidating the contents of the stack.

   Error_Resync : exception;

   --  Exception raised on error that is not handled locally, see above

   Last_Resync_Point : Source_Ptr;

   --  The resynchronization routines in Par.Sync run a risk of getting

   --  stuck in an infinite loop if they do not skip a token, and the caller

   --  keeps repeating the same resync call. On the other hand, if they skip

   --  a token unconditionally, some recovery opportunities are missed. The

   --  variable Last_Resync_Point records the token location previously set

   --  by a Resync call, and if a subsequent Resync call occurs at the same

   --  location, then the Resync routine does guarantee to skip a token.

   --------------------------------------------

   -- Handling Semicolon Used in Place of IS --

   --------------------------------------------

   --  The following global variables are used in handling the error situation

   --  of using a semicolon in place of IS in a subprogram declaration as in:

   --    procedure X (Y : Integer);

   --       Q : Integer;

   --    begin

   --       ...

   --    end;

   --  The two contexts in which this can appear are at the outer level, and

   --  within a declarative region. At the outer level, we know something is

   --  wrong as soon as we see the Q (or begin, if there are no declarations),

   --  and we can immediately decide that the semicolon should have been IS.

   --  The situation in a declarative region is more complex. The declaration

   --  of Q could belong to the outer region, and we do not know that we have

   --  an error until we hit the begin. It is still not clear at this point

   --  from a syntactic point of view that something is wrong, because the

   --  begin could belong to the enclosing subprogram or package. However, we

   --  can incorporate a bit of semantic knowledge and note that the body of

   --  X is missing, so we definitely DO have an error. We diagnose this error

   --  as semicolon in place of IS on the subprogram line.

   --  There are two styles for this diagnostic. If the begin immediately

   --  follows the semicolon, then we can place a flag (IS expected) right

   --  on the semicolon. Otherwise we do not detect the error until we hit

   --  the begin which refers back to the line with the semicolon.

   --  To control the process in the second case, the following global

   --  variables are set to indicate that we have a subprogram declaration

   --  whose body is required and has not yet been found. The prefix SIS

   --  stands for "Subprogram IS" handling.

   SIS_Entry_Active : Boolean := False;

   --  Set True to indicate that an entry is active (i.e. that a subprogram

   --  declaration has been encountered, and no body for this subprogram has

   --  been encountered). The remaining fields are valid only if this is True.

   SIS_Labl : Node_Id;

   --  Subprogram designator

   SIS_Sloc : Source_Ptr;

   --  Source location of FUNCTION/PROCEDURE keyword

   SIS_Ecol : Column_Number;

   --  Column number of FUNCTION/PROCEDURE keyword

   SIS_Semicolon_Sloc : Source_Ptr;

   --  Source location of semicolon at end of subprogram declaration

   SIS_Declaration_Node : Node_Id;

   --  Pointer to tree node for subprogram declaration

   SIS_Missing_Semicolon_Message : Error_Msg_Id;

   --  Used to save message ID of missing semicolon message (which will be

   --  modified to missing IS if necessary). Set to No_Error_Msg in the

   --  normal (non-error) case.

   --  Five things can happen to an active SIS entry

   --   1. If a BEGIN is encountered with an SIS entry active, then we have

   --   exactly the situation in which we know the body of the subprogram is

   --   missing. After posting an error message, we change the spec to a body,

   --   rechaining the declarations that intervened between the spec and BEGIN.

   --   2. Another subprogram declaration or body is encountered. In this

   --   case the entry gets overwritten with the information for the new

   --   subprogram declaration. We don't catch some nested cases this way,

   --   but it doesn't seem worth the effort.

   --   3. A nested declarative region (e.g. package declaration or package

   --   body) is encountered. The SIS active indication is reset at the start

   --   of such a nested region. Again, like case 2, this causes us to miss

   --   some nested cases, but it doesn't seen worth the effort to stack and

   --   unstack the SIS information. Maybe we will reconsider this if we ever

   --   get a complaint about a missed case.

   --   4. We encounter a valid pragma INTERFACE or IMPORT that effectively

   --   supplies the missing body. In this case we reset the entry.

   --   5. We encounter the end of the declarative region without encountering

   --   a BEGIN first. In this situation we simply reset the entry. We know

   --   that there is a missing body, but it seems more reasonable to let the

   --   later semantic checking discover this.

   ----------------------------------------------------

   -- Handling of Reserved Words Used as Identifiers --

   ----------------------------------------------------

   --  Note: throughout the parser, the terms reserved word and keyword are

   --  used interchangeably to refer to the same set of reserved keywords

   --  (including until, protected, etc).

   --  If a reserved word is used in place of an identifier, the parser where

   --  possible tries to recover gracefully. In particular, if the keyword is

   --  clearly spelled using identifier casing, e.g. Until in a source program

   --  using mixed case identifiers and lower case keywords, then the keyword

   --  is treated as an identifier if it appears in a place where an identifier

   --  is required.

   --  The situation is more complex if the keyword is spelled with normal

   --  keyword casing. In this case, the parser is more reluctant to consider

   --  it to be intended as an identifier, unless it has some further

   --  confirmation.

   --  In the case of an identifier appearing in the identifier list of a

   --  declaration, the appearance of a comma or colon right after the keyword

   --  on the same line is taken as confirmation. For an enumeration literal,

   --  a comma or right paren right after the identifier is also treated as

   --  adequate confirmation.

   --  The following type is used in calls to Is_Reserved_Identifier and

   --  also to P_Defining_Identifier and P_Identifier. The default for all

   --  these functions is that reserved words in reserved word case are not

   --  considered to be reserved identifiers. The Id_Check value indicates

   --  tokens, which if they appear immediately after the identifier, are

   --  taken as confirming that the use of an identifier was expected

   type Id_Check is

     (None,

      --  Default, no special token test

      C_Comma_Right_Paren,

      --  Consider as identifier if followed by comma or right paren

      C_Comma_Colon,

      --  Consider as identifier if followed by comma or colon

      C_Do,

      --  Consider as identifier if followed by DO

      C_Dot,

      --  Consider as identifier if followed by period

      C_Greater_Greater,

      --  Consider as identifier if followed by >>

      C_In,

      --  Consider as identifier if followed by IN

      C_Is,

      --  Consider as identifier if followed by IS

      C_Left_Paren_Semicolon,

      --  Consider as identifier if followed by left paren or semicolon

      C_Use,

      --  Consider as identifier if followed by USE

      C_Vertical_Bar_Arrow);

      --  Consider as identifier if followed by | or =>

   --------------------------------------------

   -- Handling IS Used in Place of Semicolon --

   --------------------------------------------

   --  This is a somewhat trickier situation, and we can't catch it in all

   --  cases, but we do our best to detect common situations resulting from

   --  a "cut and paste" operation which forgets to change the IS to semicolon.

   --  Consider the following example:

   --    package body X is

   --      procedure A;

   --      procedure B is

   --      procedure C;

   --      ...

   --      procedure D is

   --      begin

   --         ...

   --      end;

   --    begin

   --      ...

   --    end;

   --  The trouble is that the section of text from PROCEDURE B through END;

   --  constitutes a valid procedure body, and the danger is that we find out

   --  far too late that something is wrong (indeed most compilers will behave

   --  uncomfortably on the above example).

   --  We have two approaches to helping to control this situation. First we

   --  make every attempt to avoid swallowing the last END; if we can be sure

   --  that some error will result from doing so. In particular, we won't

   --  accept the END; unless it is exactly correct (in particular it must not

   --  have incorrect name tokens), and we won't accept it if it is immediately

   --  followed by end of file, WITH or SEPARATE (all tokens that unmistakeably

   --  signal the start of a compilation unit, and which therefore allow us to

   --  reserve the END; for the outer level.) For more details on this aspect

   --  of the handling, see package Par.Endh.

   --  If we can avoid eating up the END; then the result in the absence of

   --  any additional steps would be to post a missing END referring back to

   --  the subprogram with the bogus IS. Similarly, if the enclosing package

   --  has no BEGIN, then the result is a missing BEGIN message, which again

   --  refers back to the subprogram header.

   --  Such an error message is not too bad (it's already a big improvement

   --  over what many parsers do), but it's not ideal, because the declarations

   --  following the IS have been absorbed into the wrong scope. In the above

   --  case, this could result for example in a bogus complaint that the body

   --  of D was missing from the package.

   --  To catch at least some of these cases, we take the following additional

   --  steps. First, a subprogram body is marked as having a suspicious IS if

   --  the declaration line is followed by a line which starts with a symbol

   --  that can start a declaration in the same column, or to the left of the

   --  column in which the FUNCTION or PROCEDURE starts (normal style is to

   --  indent any declarations which really belong a subprogram). If such a

   --  subprogram encounters a missing BEGIN or missing END, then we decide

   --  that the IS should have been a semicolon, and the subprogram body node

   --  is marked (by setting the Bad_Is_Detected flag true. Note that we do

   --  not do this for library level procedures, only for nested procedures,

   --  since for library level procedures, we must have a body.

   --  The processing for a declarative part checks to see if the last

   --  declaration scanned is marked in this way, and if it is, the tree

   --  is modified to reflect the IS being interpreted as a semicolon.

   ---------------------------------------------------

   -- Parser Type Definitions and Control Variables --

   ---------------------------------------------------

   --  The following variable and associated type declaration are used by the

   --  expression parsing routines to return more detailed information about

   --  the categorization of a parsed expression.

   type Expr_Form_Type is (

      EF_Simple_Name,  -- Simple name, i.e. possibly qualified identifier

      EF_Name,         -- Simple expression which could also be a name

      EF_Simple,       -- Simple expression which is not call or name

      EF_Range_Attr,   -- Range attribute reference

      EF_Non_Simple);  -- Expression that is not a simple expression

   Expr_Form : Expr_Form_Type;

   --  The following type is used for calls to P_Subprogram, P_Package, P_Task,

   --  P_Protected to indicate which of several possibilities is acceptable.

   type Pf_Rec is record

      Spcn : Boolean;                  -- True if specification OK

      Decl : Boolean;                  -- True if declaration OK

      Gins : Boolean;                  -- True if generic instantiation OK

      Pbod : Boolean;                  -- True if proper body OK

      Rnam : Boolean;                  -- True if renaming declaration OK

      Stub : Boolean;                  -- True if body stub OK

      Pexp : Boolean;                  -- True if parametrized expression OK

      Fil2 : Boolean;                  -- Filler to fill to 8 bits

   end record;

   pragma Pack (Pf_Rec);

   function T return Boolean renames True;

   function F return Boolean renames False;

   Pf_Decl_Gins_Pbod_Rnam_Stub_Pexp : constant Pf_Rec :=

                                       Pf_Rec'(F, T, T, T, T, T, T, F);

   Pf_Decl_Pexp                     : constant Pf_Rec :=

                                       Pf_Rec'(F, T, F, F, F, F, T, F);

   Pf_Decl_Gins_Pbod_Rnam_Pexp      : constant Pf_Rec :=

                                       Pf_Rec'(F, T, T, T, T, F, T, F);

   Pf_Decl_Pbod_Pexp                : constant Pf_Rec :=

                                       Pf_Rec'(F, T, F, T, F, F, T, F);

   Pf_Pbod_Pexp                     : constant Pf_Rec :=

                                       Pf_Rec'(F, F, F, T, F, F, T, F);

   Pf_Spcn                         : constant Pf_Rec :=

                                       Pf_Rec'(T, F, F, F, F, F, F, F);

   --  The above are the only allowed values of Pf_Rec arguments

   type SS_Rec is record

      Eftm : Boolean;      -- ELSIF can terminate sequence

      Eltm : Boolean;      -- ELSE can terminate sequence

      Extm : Boolean;      -- EXCEPTION can terminate sequence

      Ortm : Boolean;      -- OR can terminate sequence

      Sreq : Boolean;      -- at least one statement required

      Tatm : Boolean;      -- THEN ABORT can terminate sequence

      Whtm : Boolean;      -- WHEN can terminate sequence

      Unco : Boolean;      -- Unconditional terminate after one statement

   end record;

   pragma Pack (SS_Rec);

   SS_Eftm_Eltm_Sreq : constant SS_Rec := SS_Rec'(T, T, F, F, T, F, F, F);

   SS_Eltm_Ortm_Tatm : constant SS_Rec := SS_Rec'(F, T, F, T, F, T, F, F);

   SS_Extm_Sreq      : constant SS_Rec := SS_Rec'(F, F, T, F, T, F, F, F);

   SS_None           : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, F, F);

   SS_Ortm_Sreq      : constant SS_Rec := SS_Rec'(F, F, F, T, T, F, F, F);

   SS_Sreq           : constant SS_Rec := SS_Rec'(F, F, F, F, T, F, F, F);

   SS_Sreq_Whtm      : constant SS_Rec := SS_Rec'(F, F, F, F, T, F, T, F);

   SS_Whtm           : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, T, F);

   SS_Unco           : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, F, T);

   Goto_List : Elist_Id;

   --  List of goto nodes appearing in the current compilation. Used to

   --  recognize natural loops and convert them into bona fide loops for

   --  optimization purposes.

   Label_List : Elist_Id;

   --  List of label nodes for labels appearing in the current compilation.

   --  Used by Par.Labl to construct the corresponding implicit declarations.

   -----------------

   -- Scope Table --

   -----------------

   --  The scope table, also referred to as the scope stack, is used to record

   --  the current scope context. It is organized as a stack, with inner nested

   --  entries corresponding to higher entries on the stack. An entry is made

   --  when the parser encounters the opening of a nested construct (such as a

   --  record, task, package etc.), and then package Par.Endh uses this stack

   --  to deal with END lines (including properly dealing with END nesting

   --  errors).

   type SS_End_Type is

   --  Type of end entry required for this scope. The last two entries are

   --  used only in the subprogram body case to mark the case of a suspicious

   --  IS, or a bad IS (i.e. suspicions confirmed by missing BEGIN or END).

   --  See separate section on dealing with IS used in place of semicolon.

   --  Note that for many purposes E_Name, E_Suspicious_Is and E_Bad_Is are

   --  treated the same (E_Suspicious_Is and E_Bad_Is are simply special cases

   --  of E_Name). They are placed at the end of the enumeration so that a

   --  test for >= E_Name catches all three cases efficiently.

      (E_Dummy,           -- dummy entry at outer level

       E_Case,            -- END CASE;

       E_If,              -- END IF;

       E_Loop,            -- END LOOP;

       E_Record,          -- END RECORD;

       E_Return,          -- END RETURN;

       E_Select,          -- END SELECT;

       E_Name,            -- END [name];

       E_Suspicious_Is,   -- END [name]; (case of suspicious IS)

       E_Bad_Is);         -- END [name]; (case of bad IS)

   --  The following describes a single entry in the scope table

   type Scope_Table_Entry is record

      Etyp : SS_End_Type;

      --  Type of end entry, as per above description

      Lreq : Boolean;

      --  A flag indicating whether the label, if present, is required to

      --  appear on the end line. It is referenced only in the case of Etyp is

      --  equal to E_Name or E_Suspicious_Is where the name may or may not be

      --  required (yes for labeled block, no in other cases). Note that for

      --  all cases except begin, the question of whether a label is required

      --  can be determined from the other fields (for loop, it is required if

      --  it is present, and for the other constructs it is never required or

      --  allowed).

      Ecol : Column_Number;

      --  Contains the absolute column number (with tabs expanded) of the

      --  expected column of the end assuming normal Ada indentation usage. If

      --  the RM_Column_Check mode is set, this value is used for generating

      --  error messages about indentation. Otherwise it is used only to

      --  control heuristic error recovery actions.

      Labl : Node_Id;

      --  This field is used to provide the name of the construct being parsed

      --  and indirectly its kind. For loops and blocks, the field contains the

      --  source name or the generated one. For package specifications, bodies,

      --  subprogram specifications and bodies the field holds the correponding

      --  program unit name. For task declarations and bodies, protected types

      --  and bodies, and accept statements the field hold the name of the type

      --  or operation. For if-statements, case-statements, and selects, the

      --  field is initialized to Error.

      --  Note: this is a bit of an odd (mis)use of Error, since there is no

      --  Error, but we use this value as a place holder to indicate that it

      --  is an error to have a label on the end line.

      --  Whenever the field is a name, it is attached to the parent node of

      --  the construct being parsed. Thus the parent node indicates the kind

      --  of construct whose parse tree is being built. This is used in error

      --  recovery.

      Decl : List_Id;

      --  Points to the list of declarations (i.e. the declarative part)

      --  associated with this construct. It is set only in the END [name]

      --  cases, and is set to No_List for all other cases which do not have a

      --  declarative unit associated with them. This is used for determining

      --  the proper location for implicit label declarations.

      Node : Node_Id;

      --  Empty except in the case of entries for IF and CASE statements, in

      --  which case it contains the N_If_Statement or N_Case_Statement node.

      --  This is used for setting the End_Span field.

      Sloc : Source_Ptr;

      --  Source location of the opening token of the construct. This is used

      --  to refer back to this line in error messages (such as missing or

      --  incorrect end lines). The Sloc field is not used, and is not set, if

      --  a label is present (the Labl field provides the text name of the

      --  label in this case, which is fine for error messages).

      S_Is : Source_Ptr;

      --  S_Is is relevant only if Etyp is set to E_Suspicious_Is or E_Bad_Is.

      --  It records the location of the IS that is considered to be

      --  suspicious.

      Junk : Boolean;

      --  A boolean flag that is set true if the opening entry is the dubious

      --  result of some prior error, e.g. a record entry where the record

      --  keyword was missing. It is used to suppress the issuing of a

      --  corresponding junk complaint about the end line (we do not want

      --  to complain about a missing end record when there was no record).

   end record;

   --  The following declares the scope table itself. The Last field is the

   --  stack pointer, so that Scope.Table (Scope.Last) is the top entry. The

   --  oldest entry, at Scope_Stack (0), is a dummy entry with Etyp set to

   --  E_Dummy, and the other fields undefined. This dummy entry ensures that

   --  Scope_Stack (Scope_Stack_Ptr).Etyp can always be tested, and that the

   --  scope stack pointer is always in range.

   package Scope is new Table.Table (

     Table_Component_Type => Scope_Table_Entry,

     Table_Index_Type     => Int,

     Table_Low_Bound      => 0,

     Table_Initial        => 50,

     Table_Increment      => 100,

     Table_Name           => "Scope");

   ---------------------------------

   -- Parsing Routines by Chapter --

   ---------------------------------

   --  Uncommented declarations in this section simply parse the construct

   --  corresponding to their name, and return an ID value for the Node or

   --  List that is created.

   -------------

   -- Par.Ch2 --

   -------------

   package Ch2 is

      function P_Pragma (Skipping : Boolean := False) return Node_Id;

      --  Scan out a pragma. If Skipping is True, then the caller is skipping

      --  the pragma in the context of illegal placement (this is used to avoid

      --  some junk cascaded messages).

      function P_Identifier (C : Id_Check := None) return Node_Id;

      --  Scans out an identifier. The parameter C determines the treatment

      --  of reserved identifiers. See declaration of Id_Check for details.

      function P_Pragmas_Opt return List_Id;

      --  This function scans for a sequence of pragmas in other than a

      --  declaration sequence or statement sequence context. All pragmas

      --  can appear except pragmas Assert and Debug, which are only allowed

      --  in a declaration or statement sequence context.

      procedure P_Pragmas_Misplaced;

      --  Skips misplaced pragmas with a complaint

      procedure P_Pragmas_Opt (List : List_Id);

      --  Parses optional pragmas and appends them to the List

   end Ch2;

   -------------

   -- Par.Ch3 --

   -------------

   package Ch3 is

      Missing_Begin_Msg : Error_Msg_Id;

      --  This variable is set by a call to P_Declarative_Part. Normally it

      --  is set to No_Error_Msg, indicating that no special processing is

      --  required by the caller. The special case arises when a statement

      --  is found in the sequence of declarations. In this case the Id of

      --  the message issued ("declaration expected") is preserved in this

      --  variable, then the caller can change it to an appropriate missing

      --  begin message if indeed the BEGIN is missing.

      function P_Array_Type_Definition                return Node_Id;

      function P_Basic_Declarative_Items              return List_Id;

      function P_Constraint_Opt                       return Node_Id;

      function P_Declarative_Part                     return List_Id;

      function P_Discrete_Choice_List                 return List_Id;

      function P_Discrete_Range                       return Node_Id;

      function P_Discrete_Subtype_Definition          return Node_Id;

      function P_Known_Discriminant_Part_Opt          return List_Id;

      function P_Signed_Integer_Type_Definition       return Node_Id;

      function P_Range                                return Node_Id;

      function P_Range_Constraint                     return Node_Id;

      function P_Record_Definition                    return Node_Id;

      function P_Subtype_Mark                         return Node_Id;

      function P_Subtype_Mark_Resync                  return Node_Id;

      function P_Unknown_Discriminant_Part_Opt        return Boolean;

      function P_Access_Definition

        (Null_Exclusion_Present : Boolean) return Node_Id;

      --  Ada 2005 (AI-231/AI-254): The caller parses the null-exclusion part

      --  and indicates if it was present

      function P_Access_Type_Definition

        (Header_Already_Parsed : Boolean := False) return Node_Id;

      --  Ada 2005 (AI-254): The formal is used to indicate if the caller has

      --  parsed the null_exclusion part. In this case the caller has also

      --  removed the ACCESS token

      procedure P_Component_Items (Decls : List_Id);

      --  Scan out one or more component items and append them to the given

      --  list. Only scans out more than one declaration in the case where the

      --  source has a single declaration with multiple defining identifiers.

      function P_Defining_Identifier (C : Id_Check := None) return Node_Id;

      --  Scan out a defining identifier. The parameter C controls the

      --  treatment of errors in case a reserved word is scanned. See the

      --  declaration of this type for details.

      function P_Interface_Type_Definition

        (Abstract_Present : Boolean) return Node_Id;

      --  Ada 2005 (AI-251): Parse the interface type definition part. Abstract

      --  Present indicates if the reserved word "abstract" has been previously

      --  found. It is used to report an error message because interface types

      --  are by definition abstract tagged. We generate a record_definition

      --  node if the list of interfaces is empty; otherwise we generate a

      --  derived_type_definition node (the first interface in this list is the

      --  ancestor interface).

      function P_Null_Exclusion

        (Allow_Anonymous_In_95 : Boolean := False) return Boolean;

      --  Ada 2005 (AI-231): Parse the null-excluding part. A True result

      --  indicates that the null-excluding part was present.

      --

      --  Allow_Anonymous_In_95 is True if we are in a context that allows

      --  anonymous access types in Ada 95, in which case "not null" is legal

      --  if it precedes "access".

      function P_Subtype_Indication

        (Not_Null_Present : Boolean := False) return Node_Id;

      --  Ada 2005 (AI-231): The flag Not_Null_Present indicates that the

      --  null-excluding part has been scanned out and it was present.

      function P_Range_Or_Subtype_Mark

        (Allow_Simple_Expression : Boolean := False) return Node_Id;

      --  Scans out a range or subtype mark, and also permits a general simple

      --  expression if Allow_Simple_Expression is set to True.

      function Init_Expr_Opt (P : Boolean := False) return Node_Id;

      --  If an initialization expression is present (:= expression), then

      --  it is scanned out and returned, otherwise Empty is returned if no

      --  initialization expression is present. This procedure also handles

      --  certain common error cases cleanly. The parameter P indicates if

      --  a right paren can follow the expression (default = no right paren

      --  allowed).

      procedure Skip_Declaration (S : List_Id);

      --  Used when scanning statements to skip past a misplaced declaration

      --  The declaration is scanned out and appended to the given list.

      --  Token is known to be a declaration token (in Token_Class_Declk)

      --  on entry, so there definition is a declaration to be scanned.

      function P_Subtype_Indication

        (Subtype_Mark     : Node_Id;

         Not_Null_Present : Boolean := False) return Node_Id;

      --  This version of P_Subtype_Indication is called when the caller has

      --  already scanned out the subtype mark which is passed as a parameter.

      --  Ada 2005 (AI-231): The flag Not_Null_Present indicates that the

      --  null-excluding part has been scanned out and it was present.

      function P_Subtype_Mark_Attribute (Type_Node : Node_Id) return Node_Id;

      --  Parse a subtype mark attribute. The caller has already parsed the

      --  subtype mark, which is passed in as the argument, and has checked

      --  that the current token is apostrophe.

   end Ch3;

   -------------

   -- Par.Ch4 --

   -------------

   package Ch4 is

      function P_Aggregate                            return Node_Id;

      function P_Expression                           return Node_Id;

      function P_Expression_Or_Range_Attribute        return Node_Id;

      function P_Function_Name                        return Node_Id;

      function P_Name                                 return Node_Id;

      function P_Qualified_Simple_Name                return Node_Id;

      function P_Qualified_Simple_Name_Resync         return Node_Id;

      function P_Simple_Expression                    return Node_Id;

      function P_Simple_Expression_Or_Range_Attribute return Node_Id;

      function P_Case_Expression return Node_Id;

      --  Scans out a case expression. Called with Token pointing to the CASE

      --  keyword, and returns pointing to the terminating right parent,

      --  semicolon, or comma, but does not consume this terminating token.

      function P_Conditional_Expression return Node_Id;

      --  Scans out a conditional expression. Called with Token pointing to

      --  the IF keyword, and returns pointing to the terminating right paren,

      --  semicolon or comma, but does not consume this terminating token.

      function P_Expression_If_OK return Node_Id;

      --  Scans out an expression allowing an unparenthesized case expression,

      --  conditional expression, or quantified expression to appear without

      --  enclosing parentheses. However, if such an expression is not preceded

      --  by a left paren, and followed by a right paren, an error message will

      --  be output noting that parenthesization is required.

      function P_Expression_No_Right_Paren return Node_Id;

      --  Scans out an expression in contexts where the expression cannot be

      --  terminated by a right paren (gives better error recovery if an errant

      --  right paren is found after the expression).

      function P_Expression_Or_Range_Attribute_If_OK return Node_Id;

      --  Scans out an expression or range attribute where a conditional

      --  expression is permitted to appear without surrounding parentheses.

      --  However, if such an expression is not preceded by a left paren, and

      --  followed by a right paren, an error message will be output noting

      --  that parenthesization is required.

      function P_Qualified_Expression (Subtype_Mark : Node_Id) return Node_Id;

      --  This routine scans out a qualified expression when the caller has

      --  already scanned out the name and apostrophe of the construct.

      function P_Quantified_Expression return Node_Id;

      --  This routine scans out a quantified expression when the caller has

      --  already scanned out the keyword "for" of the construct.

   end Ch4;

   -------------

   -- Par.Ch5 --

   -------------

   package Ch5 is

      function P_Condition return Node_Id;

      --  Scan out and return a condition

      function P_Loop_Parameter_Specification return Node_Id;

      --  Used in loop constructs and quantified expressions.

      function P_Sequence_Of_Statements (SS_Flags : SS_Rec) return List_Id;

      --  The argument indicates the acceptable termination tokens.

      --  See body in Par.Ch5 for details of the use of this parameter.

      procedure Parse_Decls_Begin_End (Parent : Node_Id);

      --  Parses declarations and handled statement sequence, setting

      --  fields of Parent node appropriately.

   end Ch5;

   -------------

   -- Par.Ch6 --

   -------------

   package Ch6 is

      function P_Designator                           return Node_Id;

      function P_Defining_Program_Unit_Name           return Node_Id;

      function P_Formal_Part                          return List_Id;

      function P_Parameter_Profile                    return List_Id;

      function P_Return_Statement                     return Node_Id;

      function P_Subprogram_Specification             return Node_Id;

      procedure P_Mode (Node : Node_Id);

      --  Sets In_Present and/or Out_Present flags in Node scanning past IN,

      --  OUT or IN OUT tokens in the source.

      function P_Subprogram (Pf_Flags : Pf_Rec)       return Node_Id;

      --  Scans out any construct starting with either of the keywords

      --  PROCEDURE or FUNCTION. The parameter indicates which possible

      --  possible kinds of construct (body, spec, instantiation etc.)

      --  are permissible in the current context.

   end Ch6;

   -------------

   -- Par.Ch7 --

   -------------

   package Ch7 is

      function P_Package (Pf_Flags : Pf_Rec) return Node_Id;

      --  Scans out any construct starting with the keyword PACKAGE. The

      --  parameter indicates which possible kinds of construct (body, spec,

      --  instantiation etc.) are permissible in the current context.

   end Ch7;

   -------------

   -- Par.Ch8 --

   -------------

   package Ch8 is

      function P_Use_Clause                           return Node_Id;

   end Ch8;

   -------------

   -- Par.Ch9 --

   -------------

   package Ch9 is

      function P_Abort_Statement                      return Node_Id;

      function P_Abortable_Part                       return Node_Id;

      function P_Accept_Statement                     return Node_Id;

      function P_Delay_Statement                      return Node_Id;

      function P_Entry_Body                           return Node_Id;

      function P_Protected                            return Node_Id;

      function P_Requeue_Statement                    return Node_Id;

      function P_Select_Statement                     return Node_Id;

      function P_Task                                 return Node_Id;

      function P_Terminate_Alternative                return Node_Id;

   end Ch9;

   --------------

   -- Par.Ch10 --

   --------------

   package Ch10 is

      function P_Compilation_Unit                     return Node_Id;

      --  Note: this function scans a single compilation unit, and checks that

      --  an end of file follows this unit, diagnosing any unexpected input as

      --  an error, and then skipping it, so that Token is set to Tok_EOF on

      --  return. An exception is in syntax-only mode, where multiple