[Ada] Implicit dereferencing in container indexing

gcc/ada/

	* sem_ch4.adb (Try_Container_Indexing): When the prefix type is
	an access type, change it to the designated type, change the
	prefix to an explicit dereference, and emit a ?d? warning for
	the implicit dereference. Include a ??? comment questioning
	whether this is the right context in which to perform the
	implicit dereferencing.

1 files changed, 20 insertions, 1 deletions

diff --git a/gcc/ada/sem_ch4.adb b/gcc/ada/sem_ch4.adb
index 8c9a0bf4dfb..76ce11d1fd5 100644
--- a/gcc/ada/sem_ch4.adb
+++ b/gcc/ada/sem_ch4.adb
@@ -7979,7 +7979,7 @@ package body Sem_Ch4 is
       Prefix : Node_Id;
       Exprs  : List_Id) return Boolean
    is
-      Pref_Typ : constant Entity_Id := Etype (Prefix);
+      Pref_Typ : Entity_Id := Etype (Prefix);
 
       function Constant_Indexing_OK return Boolean;
       --  Constant_Indexing is legal if there is no Variable_Indexing defined
@@ -8415,6 +8415,25 @@ package body Sem_Ch4 is
          return True;
       end if;
 
+      --  An explicit dereference needs to be created in the case of a prefix
+      --  that's an access.
+
+      --  It seems that this should be done elsewhere, but not clear where that
+      --  should happen. Normally Insert_Explicit_Dereference is called via
+      --  Resolve_Implicit_Dereference, called from Resolve_Indexed_Component,
+      --  but that won't be called in this case because we transform the
+      --  indexing to a call. Resolve_Call.Check_Prefixed_Call takes care of
+      --  implicit dereferencing and referencing on prefixed calls, but that
+      --  would be too late, even if we expanded to a prefix call, because
+      --  Process_Indexed_Component will flag an error before the resolution
+      --  happens. ???
+
+      if Is_Access_Type (Pref_Typ) then
+         Pref_Typ := Implicitly_Designated_Type (Pref_Typ);
+         Insert_Explicit_Dereference (Prefix);
+         Error_Msg_NW (Warn_On_Dereference, "?d?implicit dereference", N);
+      end if;
+
       C_Type := Pref_Typ;
 
       --  If indexing a class-wide container, obtain indexing primitive from