[PATCH] ada: Warn if enumeration representation clause is not honored in record

[Samuel Tardieu]

If an enumeration type E has a representation clause, GNAT will ignore
it silently if it is used as a component type in a record which has a
representation clause. This patch adds a warning in this case. The attached
test program gives:

    12.       A1 at 0 range 0 .. 0;
                 |
        >>> warning: component representation will be biased

Bootstrapped and tested on i686-pc-linux-gnu.

Ok for trunk?

    gcc/ada/
	* sem_ch13.adb (Analyze_Record_Representation_Clause): Warn if
	enumeration representation cannot be honored in record.

    gcc/testsuite/
	* gnat.dg/specs/biased_enum.ads: New.
---
 gcc/ada/sem_ch13.adb                        |    8 ++++++++
 gcc/testsuite/gnat.dg/specs/biased_enum.ads |   17 +++++++++++++++++
 2 files changed, 25 insertions(+), 0 deletions(-)
 create mode 100644 gcc/testsuite/gnat.dg/specs/biased_enum.ads

diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb
index f72ffff..8b5e555 100644
--- a/gcc/ada/sem_ch13.adb
+++ b/gcc/ada/sem_ch13.adb
@@ -2491,6 +2491,14 @@ package body Sem_Ch13 is
 
                         Set_Has_Biased_Representation (Comp, Biased);
 
+                        if Biased
+                          and then Has_Enumeration_Rep_Clause (Etype (Comp))
+                        then
+                           Error_Msg_N
+                             ("?component representation will be biased",
+                              CC);
+                        end if;
+
                         if Present (Ocomp) then
                            Set_Component_Clause     (Ocomp, CC);
                            Set_Component_Bit_Offset (Ocomp, Fbit);
diff --git a/gcc/testsuite/gnat.dg/specs/biased_enum.ads b/gcc/testsuite/gnat.dg/specs/biased_enum.ads
new file mode 100644
index 0000000..2088336
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/specs/biased_enum.ads
@@ -0,0 +1,17 @@
+-- { dg-do "compile" }
+package Biased_Enum is
+   type ENUM_T is (ONE, TWO);
+   for ENUM_T use (ONE => 1, TWO => 2);
+   for ENUM_T'Size use 2;
+
+   type RECORD_T is record
+      A1 : ENUM_T;
+      A2 : ENUM_T;
+   end record;
+   for RECORD_T use record
+      A1 at 0 range 0 .. 0; -- { dg-warning "will be biased" }
+      A2 at 1 range 0 .. 7;
+   end record;
+   for RECORD_T'Size use 2 * 8;
+
+end Biased_Enum;
-- 
1.5.6.rc2.304.ga7c8