[Ada] Unnesting bugs with array renamings generated for quantified expr

2020-06-02  Gary Dismukes  <dismukes@adacore.com>

gcc/ada/

	* exp_unst.adb (Visit_Node): When visiting array attribute
	nodes, apply Get_Referenced_Object to the attribute prefix, to
	handle prefixes denoting renamed objects by picking up the Etype
	of the renamed object rather than the possibly unconstrained
	nominal subtype of the renaming declaration's Entity.
	* sem_util.ads (Get_Referenced_Object): Update comment to
	clearly indicate that any kind of node can be passed to this
	function.
	* sem_util.adb (Get_Referenced_Object): Add test of Is_Object to
	the condition, to allow for passing names that denote types and
	subtypes.

gcc/ada/exp_unst.adb

@@ -1042,14 +1042,21 @@ package body Exp_Unst is
                            --  handled during full traversal. Note that if the
                            --  nominal subtype of the prefix is unconstrained,
                            --  the bound must be obtained from the object, not
-                           --  from the (possibly) uplevel reference.
+                           --  from the (possibly) uplevel reference. We call
+                           --  Get_Referenced_Object to deal with prefixes that
+                           --  are object renamings (prefixes that are types
+                           --  can be passed and will simply be returned).
 
-                           if Is_Constrained (Etype (Prefix (N))) then
+                           if Is_Constrained
+                                (Etype (Get_Referenced_Object (Prefix (N))))
+                           then
                               declare
                                  DT : Boolean := False;
                               begin
                                  Check_Static_Type
-                                   (Etype (Prefix (N)), Empty, DT);
+                                   (Etype (Get_Referenced_Object (Prefix (N))),
+                                    Empty,
+                                    DT);
                               end;
 
                               return OK;

gcc/ada/sem_util.adb

@@ -10181,6 +10181,7 @@ package body Sem_Util is
    begin
       R := N;
       while Is_Entity_Name (R)
+        and then Is_Object (Entity (R))
         and then Present (Renamed_Object (Entity (R)))
       loop
          R := Renamed_Object (Entity (R));

gcc/ada/sem_util.ads

@@ -1138,9 +1138,10 @@ package Sem_Util is
    --  corresponding aspect.
 
    function Get_Referenced_Object (N : Node_Id) return Node_Id;
-   --  Given a node, return the renamed object if the node represents a renamed
-   --  object, otherwise return the node unchanged. The node may represent an
-   --  arbitrary expression.
+   --  Given an arbitrary node, return the renamed object if the node
+   --  represents a renamed object; otherwise return the node unchanged.
+   --  The node can represent an arbitrary expression or any other kind of
+   --  node (such as the name of a type).
 
    function Get_Renamed_Entity (E : Entity_Id) return Entity_Id;
    --  Given an entity for an exception, package, subprogram or generic unit,