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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - coroutine_traits on lambda without state"
href="https://bugs.llvm.org/show_bug.cgi?id=42107">42107</a>
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<th>Summary</th>
<td>coroutine_traits on lambda without state
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>8.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++2a
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>adi@thingdust.com
</td>
</tr>
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Hi. I'm not sure what the standard does say about this, but to me it sounds
like a bug.
The following code should work in my opinion (on godbolt:
<a href="https://godbolt.org/z/1gRoaD">https://godbolt.org/z/1gRoaD</a>):
#include <experimental/coroutine>
template <typename T>
struct task {};
template <typename Ret, typename... Args>
struct std::experimental::coroutine_traits<task<Ret>, Args...> {
static_assert(sizeof...(Args) == 0);
struct promise_type {
std::experimental::suspend_never initial_suspend() { return {}; }
std::experimental::suspend_never final_suspend() { return {}; }
void return_void() { }
task<Ret> get_return_object(){ return {}; }
void unhandled_exception(){ std::terminate(); }
};
};
//works:
task<void> foo() {
co_return;
}
int main() {
//does not work:
auto bar = []() -> task<void> {
co_return;
};
}
The background is that I am trying to differentiate between "safe" coroutines
(coroutines which cannot hold state from the caller: this ptr, reference
parameters, ...) and "unsafe" coroutines (free functions with only value
parameters).</pre>
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