[Ada] Spurious error on aggregate with choice that is predicted subtype

[Pierre-Marie de Rodat]

This patch fixes a spurious error on a record aggregate for a variant
record when a choice in the aggregate is given by a subtype with a
static predicate. The same expansion mechanism for such a variant, used
in case statements, must be used here as well.

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

2019-07-05  Ed Schonberg  <schonb...@adacore.com>

gcc/ada/

        * sem_util.adb (Encloing_Subprogram): If Enclosing_Dynamic_Scope
        is a loop, continue climbing the scope stack to find the
        enclosing subprogram.
        (Gather_Components): Handle properly a choice in a record
        aggregate that is given by a subtype with a static predicate.

gcc/testsuite/

        * gnat.dg/aggr25.adb, gnat.dg/aggr25.ads: New testcase.
--- gcc/ada/sem_util.adb
+++ gcc/ada/sem_util.adb
@@ -6895,7 +6895,7 @@ package body Sem_Util is
       elsif Ekind (Dyn_Scop) = E_Subprogram_Body then
          return Corresponding_Spec (Parent (Parent (Dyn_Scop)));
 
-      elsif Ekind_In (Dyn_Scop, E_Block, E_Return_Statement) then
+      elsif Ekind_In (Dyn_Scop, E_Block, E_Return_Statement, E_Loop) then
          return Enclosing_Subprogram (Dyn_Scop);
 
       elsif Ekind (Dyn_Scop) = E_Entry then
@@ -8939,6 +8939,12 @@ package body Sem_Util is
 
       begin
          Find_Discrete_Value : while Present (Variant) loop
+
+            --  If a choice is a subtype with a static predicate, it must
+            --  be rewritten as an explicit list of non-predicated choices.
+
+            Expand_Static_Predicates_In_Choices (Variant);
+
             Discrete_Choice := First (Discrete_Choices (Variant));
             while Present (Discrete_Choice) loop
                exit Find_Discrete_Value when

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/aggr25.adb
@@ -0,0 +1,7 @@
+--  { dg-do compile }
+
+package body Aggr25 is
+
+  procedure Foo is null;
+
+end Aggr25;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/aggr25.ads
@@ -0,0 +1,23 @@
+package Aggr25 is
+
+  type T_A is (A, B , C ,D);
+
+  subtype Has_B_D is T_A with Static_Predicate => Has_B_D in B | D;
+
+  type Obj_T (Kind : T_A) is
+    record
+       case Kind is
+        --OK-- when A | C => null; --OK--
+        when Has_B_D  =>  Value : Boolean;
+        --BAD-- when A | C => null;
+        when others => null;
+      end case;
+    end record;
+
+  type T is access Obj_T;
+
+  Unavailable : constant T := new Obj_T'(Kind => A);
+
+  procedure Foo;
+
+end Aggr25;