Bug#882855: g++-7: internal compiler error: in maybe_undo_parenthesized_ref on for initialization list

[David Cadé <codename_68@hotmail.com>]

Package: g++-7
Version: 7.2.0-16
Severity: important

Dear Maintainer,

The following C++ program, when compiled with g++, returns an internal compiler error.

--------
int rand();

template<typename T>
struct s
{
    int count() { return rand(); }
};

template<typename v>
int f(s<v> a)
{
    int const x = a.count();
    int r = 0;
    auto l = [&](int& r)
    {
        for(int y = 0, yend = (x); y < yend; ++y)
        {
            r += y;
        }
    };
    l(r);
}

template int f(s<float>);

int main()
{
}
--------

g++ test.cpp returns:
--------
test.cpp: In instantiation of ‘f(s<v>)::<lambda(int&)> [with v = float]’:
test.cpp:14:16:   required from ‘struct f(s<v>) [with v = float]::<lambda(int&)>’
test.cpp:14:10:   required from ‘int f(s<v>) [with v = float]’
test.cpp:24:24:   required from here
test.cpp:16:24: internal compiler error: in maybe_undo_parenthesized_ref, at cp/semantics.c:1705
         for(int y = 0, yend = (x); y < yend; ++y)
                        ^~~~
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.
--------

Thanks!


-- System Information:
Debian Release: buster/sid
  APT prefers unstable
  APT policy: (900, 'unstable'), (500, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.13.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages g++-7 depends on:
ii  gcc-7            7.2.0-16
ii  gcc-7-base       7.2.0-16
ii  libc6            2.24-17
ii  libgmp10         2:6.1.2+dfsg-1.1
ii  libisl15         0.18-1
ii  libmpc3          1.0.3-2
ii  libmpfr4         3.1.6-1
ii  libstdc++-7-dev  7.2.0-16
ii  zlib1g           1:1.2.8.dfsg-5

g++-7 recommends no packages.

Versions of packages g++-7 suggests:
ii  g++-7-multilib    7.2.0-16
pn  gcc-7-doc         <none>
pn  libstdc++6-7-dbg  <none>

-- no debconf information