The compiler was disallowing an access to a container to be used as the
prefix of an indexing of the container, but implicit dereferencing is
allowed in such a context (basically because a prefix can be an
implicit_dereference, by RM 4.1(4); a Ramification note was added in RM
4.1.6(11.a/5), to clarify that this works).
Tested on x86_64-pc-linux-gnu, committed on trunk
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.diff --git a/gcc/ada/sem_ch4.adb b/gcc/ada/sem_ch4.adb
--- 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
