[Bug c++/106398] New: ICE in finish_expr_stmt at cp/semantics.c:872 for lambda with conditional noexcept against lambda in unevaluated context

[Bug c++/106398] New: ICE in finish_expr_stmt at cp/semantics.c:872 for lambda with conditional noexcept against lambda in unevaluated context

[jbassett271 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106398

            Bug ID: 106398
           Summary: ICE in finish_expr_stmt at cp/semantics.c:872 for
                    lambda with conditional noexcept against lambda in
                    unevaluated context
           Product: gcc
           Version: 12.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jbassett271 at gmail dot com
  Target Milestone: ---

This ICEs:

#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}


#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}


#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}


#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}

#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}


https://godbolt.org/z/hPYP8s9W7

I've seen this ICE on several versions of GCC, including 11.1.0, 10.3.0, and
this 12.1.1.

This is possibly https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105692, but I
don't know enough to deduplicate.

This may be related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101043.

[Bug c++/106398] ICE in finish_expr_stmt at cp/semantics.c:872 for lambda with conditional noexcept against lambda in unevaluated context

[jbassett271 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106398

--- Comment #1 from Justin Bassett <jbassett271 at gmail dot com> ---
Sorry about the repetition of the code example. That was some kind of bug in
the website or browser where the pasted text did not show up except for the
last copy. Let's give that code snippet one more time to make it more clearly
delineated:

#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <bool B>
struct bool_t { static constexpr bool value = B; };

template <typename T>
struct set {
  bool contains(T const&) const { return true; }
};

template <typename T>
void intersect(set<T> const& lhs, set<T> const& rhs) {
  auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      return bool_t<noexcept(rhs.contains(_1))>{};
  }(FWD(_1)))::value) {
      return rhs.contains(_1);
  };
  f(1);
}

int main() 
{
    set<int> a, b;
    intersect(a, b);
}

[Bug c++/106398] ICE in finish_expr_stmt at cp/semantics.c:872 for lambda with conditional noexcept against lambda in unevaluated context

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106398

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-07-22

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r9-4045-g0c1e0d63fe0ceabb, it was rejected before the revision
with:

pr106398.c: In function ‘void intersect(const set<T>&, const set<T>&)’:
pr106398.c:13:56: error: lambda-expression in unevaluated context
   13 |   auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      |                                                        ^
pr106398.c:13:47: error: decltype evaluates to ‘<type error>’, which is not a
class or enumeration type
   13 |   auto f = [&]<typename T1>(T1&& _1) noexcept(decltype([] {
      |                                               ^~~~~~~~

[Bug c++/106398] ICE in finish_expr_stmt at cp/semantics.c:872 for lambda with conditional noexcept against lambda in unevaluated context

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106398

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|NEW                         |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup.

*** This bug has been marked as a duplicate of bug 109241 ***