[Bug c++/61683] New: decltype-specifier not accepted as mem-initializer-id

["bbi5291 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61683

            Bug ID: 61683
           Summary: decltype-specifier not accepted as mem-initializer-id
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bbi5291 at gmail dot com

$ cat main.cpp
struct A {};
A a;
struct B : A {
    B(): decltype(a)() {}
};
int main() {}

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --program-suffix=-4.9.0
Thread model: posix
gcc version 4.9.0 (GCC) 

$ g++-4.9.0 -std=c++11 main.cpp
main.cpp: In constructor ‘B::B()’:
main.cpp:4:10: error: expected identifier before ‘decltype’
     B(): decltype(a)() {}
          ^
main.cpp:4:10: error: expected ‘{’ before ‘decltype’

--

This code should compile because the standard says that any class-or-decltype
that denotes a base class can be used in a mem-initializer-list.

clang accepts: http://coliru.stacked-crooked.com/a/b50333efbcab9d26
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From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/61382] parameter pack expansion  unexpected order
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ida382

--- Comment #10 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Brooks Moses from comment #9)
> FWIW, the new initlist86.C test that this adds is failing on the
> google/gcc-4_9 branch on powerpc64le and aarch64, though it passes on
> x86_64.  I haven't yet checked on the upstream 4.9 branch, but I figured a
> heads-up might be useful.

Thanks.  Does removing "PUSH_ARGS_REVERSED &&" from the cp_gimplify_expr change
fix it?