[Bug c++/115851] New: ICE in gimplify_var_or_parm_decl with coroutine suspension point inside statement expression

[Bug c++/115851] New: ICE in gimplify_var_or_parm_decl with coroutine suspension point inside statement expression

[daklishch at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115851

            Bug ID: 115851
           Summary: ICE in gimplify_var_or_parm_decl with coroutine
                    suspension point inside statement expression
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daklishch at gmail dot com
  Target Milestone: ---

The following snippet ICEs GCC if the later is invoked with -std=c++20
-fno-exceptions

```
namespace std {
template <typename _Result>
struct coroutine_traits : _Result {};
template <typename = void>
struct coroutine_handle {
    operator coroutine_handle<>();
};
}  // namespace std

struct SuspendNever {
    bool await_ready();
    void await_suspend(std::coroutine_handle<>);
    void await_resume();
};

struct PromiseType {
    void get_return_object();
    SuspendNever initial_suspend();
    SuspendNever final_suspend();
};

struct Coroutine {
    using promise_type = PromiseType;
};

struct ErrorOr {
    int release_error();
};

void warnln(int const&);

Coroutine __async_test_input_basic() {
    ({
        co_await SuspendNever{};
        ErrorOr _temporary_result2;
        warnln(_temporary_result2.release_error());
    });
}
```

(if you prefer standard-complying code, replace std namespace with #include
<coroutine>)

CE link: https://godbolt.org/z/ePrP7rh73

[Bug c++/115851] ICE in gimplify_var_or_parm_decl with coroutine suspension point inside statement expression

[daklishch at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115851

--- Comment #1 from Dan Klishch <daklishch at gmail dot com> ---
GCC seems to do checks for coroutine-related types more eagerly now, so the
original minified reproducer is rejected. Nonetheless, the underlying issue
persists, which can be shown using this snippet:

```
#include <coroutine>

struct SuspendNever {
    bool await_ready();
    void await_suspend(std::coroutine_handle<>);
    void await_resume();
};

struct Coroutine;

struct PromiseType {
    Coroutine get_return_object();
    SuspendNever initial_suspend();
    SuspendNever final_suspend();
};

struct Coroutine {
    using promise_type = PromiseType;
};

struct ErrorOr {
    int release_error();
};

void warnln(int const&);

Coroutine __async_test_input_basic() {
    ({
        co_await SuspendNever{};
        ErrorOr _temporary_result2;
        warnln(_temporary_result2.release_error());
    });
}
```

CE link: https://godbolt.org/z/aG588Whv6

[Bug c++/115851] ICE in gimplify_var_or_parm_decl with coroutine suspension point inside statement expression

[arsen at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115851

Arsen Arsenović <arsen at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |arsen at gcc dot gnu.org

--- Comment #2 from Arsen Arsenović <arsen at gcc dot gnu.org> ---
thanks for the updated testcase - indeed, we haven't fixed the underlying cause
yet (we do plan on doing it soon).