[Bug c++/95824] New: [coroutines] compiler crash

[victor.burckel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95824

            Bug ID: 95824
           Summary: [coroutines] compiler crash
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: victor.burckel at gmail dot com
  Target Milestone: ---

The following code sample makes the gcc 10.1.0 compiler crash with segmentation
fault (compiled with -std=c++20 -fcoroutines). Gcc trunk generates an assertion
> internal compiler error: tree check: expected function_type or method_type, have pointer_type in captures_temporary, at cp/coroutines.cc:2690

That's the smallest piece of code I was able to reproduce on gcc 10.1.0
(removing the virtual from the makeId method or removing the virtual
inheritance from the exception fixes the issue). 
On gcc trunk the exception and base classes are not necessary to generate the
assertion.

I initially got this issue when invoking a virtual method to get a feed a
parameter to a coroutine, with boost::archive::archive_exception included,
which virtually inherits from std::exception.

I managed to reproduce with godbolt
https://godbolt.org/z/tBmRxJ

#include <coroutine>

struct task {
  struct promise_type {
    auto initial_suspend() noexcept { return std::suspend_always{}; }
    auto final_suspend() noexcept { return std::suspend_always{}; }
    void return_void() {}
    task get_return_object() { return task{}; }
    void unhandled_exception() noexcept {}
  };

  ~task() noexcept {}

  bool await_ready() const noexcept { return false; }
  void await_suspend(std::coroutine_handle<>) noexcept {}
  void await_resume() noexcept {}
};

struct base
{
    virtual ~base() = default;
};

class exception : public virtual base
{};

struct factory
{
    virtual ~factory() = default;
    virtual int makeId() const;
};

task g(int);

task f(factory& factory) {
    co_await g(factory.makeId());
}