[llvm-bugs] [Bug 43120] New: Complex nested lambda crashes Clang frontend

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43120

            Bug ID: 43120
           Summary: Complex nested lambda crashes Clang frontend
           Product: clang
           Version: 8.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: jonathan.barnard at grasshopperasia.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Created attachment 22430
  --> https://bugs.llvm.org/attachment.cgi?id=22430&action=edit
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;
}

https://godbolt.org/z/_iWHWd 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.

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