This assertion is triggered by the following well-formed (AFAIK) code (tested on trunk):

template<typename Fn>
struct fun : Fn
{
    fun() = default;
    fun(Fn fn) : Fn(fn) {}
    using Fn::operator();
};

template<typename Fn>
fun<Fn> wrap(Fn fn)
{
    return fun<Fn>(fn);
}

int main()
{
    wrap([](){});
}

Bit of a PITA. I haven't found a work-around.

Fixed in r228785.

Eric's rejects-valid with lambdas is fixed, the testcase produced by the fuzzer still fails, and looks like an unrelated error-recovery issue.

No longer reproduces on trunk: https://godbolt.org/z/ojxPe9qsG

Looks like it was fixed after clang-3

@llvm/issue-subscribers-clang-frontend

The second example doesn't reproduce even with assertions builds: https://godbolt.org/z/4jdhcrrso
But the original example still crashes: https://godbolt.org/z/nPqcjMvT3