[Ada] Check that actual for aliased parameter is aliased

[Arnaud Charlet <charlet at adacore dot com>]

This next step in implementing Ada 2012 AI 142 adds the check that
the actual for an aliased parameter is itself aliased, as shown by
the following example:

     1. pragma Ada_2012;
     2. with Text_IO; use Text_IO;
     3. procedure AliasP3 is
     4.    G : Integer;
     5.
     6.    procedure K  (R : aliased in out Integer) is
     7.    begin
     8.       G := 2;
     9.       R := 5;
    10.       Put_Line (G'Img);
    11.    end;
    12. begin
    13.    K (G);
              |
        >>> actual for aliased formal "R" must be aliased object

    14. end;

The previously filed test which is supposed to execute is modified
to be:

     1. pragma Ada_2012;
     2. with Text_IO; use Text_IO;
     3. procedure AliasP1 is
     4.    G : aliased Integer;
     5.
     6.    procedure K  (R : aliased in out Integer) is
     7.    begin
     8.       G := 2;
     9.       R := 5;
    10.       Put_Line (G'Img);
    11.    end;
    12. begin
    13.    K (G);
    14. end;

which compiles fine and generates the output 5.

An additional test is filed showing aliased parameters working OK:

     1. pragma Ada_2012;
     2. with Text_IO; use Text_IO;
     3. procedure AliasP2 is
     4.    G : aliased Integer;
     5.
     6.    procedure K  (R : aliased in out Integer) is
     7.       type A is access all Integer;
     8.       AA : A;
     9.    begin
    10.       G := 2;
    11.       AA := R'access;
    12.       AA.all := 6;
    13.       Put_Line (G'Img);
    14.    end;
    15. begin
    16.    K (G);
    17. end;

which compiles fine and generates the output 6

Tested on x86_64-pc-linux-gnu, committed on trunk

2011-09-01  Robert Dewar  <dewar@adacore.com>

	* exp_ch6.adb (Expand_Call): Check actual for aliased parameter is
	aliased.

Attachment: difs
Description: Text document