[Bug c++/54277] New: Template class member referred to with implicit this inside lambda is incorrectly const-qualified

["travis at gockelhut dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54277

             Bug #: 54277
           Summary: Template class member referred to with implicit this
                    inside lambda is incorrectly const-qualified
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: travis@gockelhut.com


Created attachment 28025
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28025
reproduce -- fails in 4.7.0, works in 4.6.3

When a template class attempts to call a member's member function inside of a
lambda function AND the member is referred to through an implicit this, the
member will be erroneously const-qualified.

    struct Used
    {
        void foo() { }
    };

    template <typename>
    struct S
    {
        Used x;

        void bar()
        {
            auto f = [this] { x.foo(); };
            f();
        }
    };

Yields the following compilation error with g++ 4.7:

capture-this-const.cpp: In lambda function:
capture-this-const.cpp:13:27: error: no matching function for call to
âUsed::foo() constâ
capture-this-const.cpp:13:27: note: candidate is:
capture-this-const.cpp:3:7: note: void Used::foo() <near match>
capture-this-const.cpp:3:7: note:   no known conversion for implicit âthisâ
parameter from âconst Used*â to âUsed*â

---

This can be compiled properly by explicitly adding this->:

            auto f = [this] { this->x.foo(); };

---

$> g++ -v
Using built-in specs.
COLLECT_GCC=g++-4.7
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.7.0-7ubuntu3' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --disable-bootstrap --with-sysroot=/
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
--enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror
--with-arch-32=i686 --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.0 (Ubuntu/Linaro 4.7.0-7ubuntu3)