[Ada] Spurious error in case expression of static predicate subtype

[Arnaud Charlet <charlet at adacore dot com>]

This patch corrects the implementation of static predicates in the context of
case expressions and/or statements. The maching of individual case alternatives
is now done against the sets of legal values defined by the static predicate.

------------
-- Source --
------------

--  static_predicates.adb

procedure Static_Predicates is
   type Typ is (A, B, C, D, E, F, G, H, I, J, K, L, M, N);

   subtype Subtyp is Typ with
     Static_Predicate => Subtyp in D .. F | H | J .. L;

   --  0  1  2  3  4  5  6  7  8  9  10 11 12 13
   --          +-------+   +-+   +-------+
   --  A  B  C |D  E  F| G |H| I |J  K  L| M  N
   --          +-------+   +-+   +-------+

   Obj : Subtyp;

begin
   case Obj is
      when A .. B => null;  --  A .. B  illegal
   end case;
   case Obj is
      when B .. D => null;  --  B .. C  illegal
   end case;
   case Obj is              --  missing F, H, J .. L
      when D .. E => null;
   end case;
   case Obj is
      when E .. G => null;  --  G  illegal
   end case;
   case Obj is
      when F .. H => null;  --  G  illegal
   end case;
   case Obj is              --  missing D .. F
      when G .. H => null;  --  G  illegal
   end case;
   case Obj is              --  missing D .. F
      when H .. I => null;  --  I  illegal
   end case;
   case Obj is              --  missing D .. F, H
      when I .. M => null;  --  I illegal
   end case;
   case Obj is              --  ok
      when D .. F => null;
      when H      => null;
      when J .. L => null;
   end case;
   case Obj is
      when D .. E => null;
      when G .. N => null;  --  G  illegal
      when others => null;
   end case;
   case Obj is
      when D      => null;
      when D .. F => null;  --  D  duplicated
      when H      => null;
      when J .. L => null;
   end case;
   case Obj is
      when D .. F => null;
      when H      => null;
      when J .. L => null;
      when J      => null;  --  J  duplicated
   end case;
end Static_Predicates;

----------------------------
-- Compilation and output --
----------------------------

gcc -c -gnat12 static_predicates.adb
static_predicates.adb:16:14: static predicate on "Subtyp" excludes range
  "A" .. "B"
static_predicates.adb:19:14: static predicate on "Subtyp" excludes range
  "B" .. "C"
static_predicates.adb:21:04: missing case value: "F"
static_predicates.adb:21:04: missing case value: "H"
static_predicates.adb:21:04: missing case values: "J" .. "L"
static_predicates.adb:25:14: static predicate on "Subtyp" excludes value "G"
static_predicates.adb:28:14: static predicate on "Subtyp" excludes value "G"
static_predicates.adb:30:04: missing case values: "D" .. "F"
static_predicates.adb:31:14: static predicate on "Subtyp" excludes value "G"
static_predicates.adb:33:04: missing case values: "D" .. "F"
static_predicates.adb:34:14: static predicate on "Subtyp" excludes value "I"
static_predicates.adb:36:04: missing case values: "D" .. "F"
static_predicates.adb:36:04: missing case value: "H"
static_predicates.adb:37:14: static predicate on "Subtyp" excludes value "I"
static_predicates.adb:46:14: static predicate on "Subtyp" excludes value "G"
static_predicates.adb:50:12: duplication of choice value
static_predicates.adb:58:14: duplication of choice value

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

2013-04-11  Hristian Kirtchev  <kirtchev@adacore.com>

	* sem_case.adb (Check_Against_Predicate): New routine.
	(Check_Choices): When the type covered by the list of choices
	is a static subtype with a static predicate, check all choices
	agains the predicate.
	(Issue_Msg): All versions removed.
	(Missing_Choice): New routines.
	* sem_ch4.adb: Code and comment reformatting.
	(Analyze_Case_Expression): Do not check the choices when the case
	expression is being preanalyzed and the type of the expression
	is a subtype with a static predicate.
	(Has_Static_Predicate): New routine.
	* sem_ch13.adb: Code and comment reformatting.	(Build_Range):
	Always build a range even if the low and hi bounds denote the
	same value. This is needed by the machinery in Check_Choices.
	(Build_Static_Predicate): Always build a range even if the low and
	hi bounds denote the same value. This is needed by the machinery
	in Check_Choices.

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