[Ada] Cleanup repeated code for aggregate constraints checks

[Pierre-Marie de Rodat <derodat@adacore.com>]

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Code cleanup related to examining uses of Check_Unset_Reference for
improved detection of uninitialised scalar objects. Semantics is
unaffected.

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

gcc/ada/

	* sem_util.adb (Aggregate_Constraint_Checks): Fix whitespace;
	refactor repeated code; replace a ??? comment with an
	explanation based on the comment for the routine spec.

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diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -1153,7 +1153,7 @@ package body Sem_Util is
      (Exp       : Node_Id;
       Check_Typ : Entity_Id)
    is
-      Exp_Typ : constant Entity_Id  := Etype (Exp);
+      Exp_Typ : constant Entity_Id := Etype (Exp);
 
    begin
       if Raises_Constraint_Error (Exp) then
@@ -1236,12 +1236,12 @@ package body Sem_Util is
         and then Is_Scalar_Type (Check_Typ)
         and then Exp_Typ /= Check_Typ
       then
+         --  If expression is a constant, it is worthwhile checking whether it
+         --  is a bound of the type.
+
          if Is_Entity_Name (Exp)
            and then Ekind (Entity (Exp)) = E_Constant
          then
-            --  If expression is a constant, it is worthwhile checking whether
-            --  it is a bound of the type.
-
             if (Is_Entity_Name (Type_Low_Bound (Check_Typ))
                  and then Entity (Exp) = Entity (Type_Low_Bound (Check_Typ)))
               or else
@@ -1249,20 +1249,15 @@ package body Sem_Util is
                  and then Entity (Exp) = Entity (Type_High_Bound (Check_Typ)))
             then
                return;
-
-            else
-               Rewrite (Exp, Convert_To (Check_Typ, Relocate_Node (Exp)));
-               Analyze_And_Resolve (Exp, Check_Typ);
-               Check_Unset_Reference (Exp);
             end if;
+         end if;
 
-         --  Could use a comment on this case ???
+         --  Change Exp into Check_Typ'(Exp) to ensure that range checks are
+         --  performed at run time.
 
-         else
-            Rewrite (Exp, Convert_To (Check_Typ, Relocate_Node (Exp)));
-            Analyze_And_Resolve (Exp, Check_Typ);
-            Check_Unset_Reference (Exp);
-         end if;
+         Rewrite (Exp, Convert_To (Check_Typ, Relocate_Node (Exp)));
+         Analyze_And_Resolve (Exp, Check_Typ);
+         Check_Unset_Reference (Exp);
 
       end if;
    end Aggregate_Constraint_Checks;