[Bug ada/82746] New: strange error on BIP function returning private type with Disable_Controlled

[demoonlit at panathenaia dot halfmoon.jp]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82746

            Bug ID: 82746
           Summary: strange error on BIP function returning private type
                    with Disable_Controlled
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: demoonlit at panathenaia dot halfmoon.jp
  Target Milestone: ---

Created attachment 42488
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42488&action=edit
bug triggering source code

The compiler outputs strange error message ("" is undefined) on a
build-in-place function returning a type derived from a private type with
Disable_Controlled => True.

Compile the attached file:

% gcc -c pkg.adb
pkg.adb:17:07: "" is undefined

--------
   function BIP_2 return T is
   begin
      return Result : T do -- pkg.adb:17:07: "" is undefined
         null;
      end return;
   end BIP_2;
--------