Why does this code compile (C++11) without a type mismatch error?

You’re not calling vector‘s constructor that takes an initializer_list<char>. That constructor is not viable because, as you said, you’re not passing a list of chars.

But vector also has a constructor that takes iterators to a range of elements.

template< class InputIt >
vector( InputIt first, InputIt last,
        const Allocator& alloc = Allocator() );

Unfortunately, this constructor matches because the two arguments will each implicitly convert to char const *. But your code has undefined behavior because the begin and end iterators being passed to the constructor are not a valid range.