<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Complex nested lambda crashes Clang frontend"
   href="https://bugs.llvm.org/show_bug.cgi?id=43120">43120</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Complex nested lambda crashes Clang frontend
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>8.0
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>jonathan.barnard@grasshopperasia.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=22430" name="attach_22430" title="The Clang stack trace">attachment 22430</a> <a href="attachment.cgi?id=22430&action=edit" title="The Clang stack trace">[details]</a></span>
The Clang stack trace

The following C++17 code causes the compiler to crash, when compiling with
-std=c++17 -O0 -emit-llvm:

#include <functional>
#include <type_traits>

template <typename F>
constexpr auto curry(F&& f) {
  if constexpr (std::is_invocable_v<F>) {
    return f();
  } else {
    return [f = static_cast<F&&>(f)](auto&& arg) mutable {
      return curry([
        f = static_cast<F&&>(f),
        arg_t = std::forward_as_tuple(static_cast<decltype(arg)&&>(arg))
      ](auto&&... args) mutable->decltype(f(static_cast<decltype(arg)&&>(arg),
                                            static_cast<decltype(args)&&>(
                                                args)...)) {
        return std::apply(
            f, std::tuple_cat(std::move(arg_t),
                              std::forward_as_tuple(
                                  static_cast<decltype(args)&&>(args)...)));
      });
    };
  }
}

int main(){
    int n;
    auto f = [](int n, int m, int x) { return n + m + x; };

    auto c1 = curry(f)(n);
    return 0;
}

<a href="https://godbolt.org/z/_iWHWd">https://godbolt.org/z/_iWHWd</a> is a link demonstrating it. It crashes on x86-64
Clang 8.0 and trunk, but seems not to crash on the Experimental Concepts Clang
build.</pre>
        </div>
      </p>


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