Since NonnullRefPtr and NonnullOwnPtr cannot be null, it is pointless
to convert them to a bool, since it would always be true.
This patch makes it an error to null-check one of these pointers.
Add the concept of a PeekType to Traits<T>. This is the type we'll
return (wrapped in an Optional) from HashMap::get().
The PeekType for OwnPtr<T> and NonnullOwnPtr<T> is const T*,
which means that HashMap::get() will return an Optional<const T*> for
maps-of-those.
Add an "ElementType" typedef to NonnullOwnPtr and NonnullRefPtr to allow
clients to easily find the pointee type. Then use this to remove a template
argument from NonnullPtrVector. :^)
This is just like OwnPtr (also single-owner), except it cannot be null.
NonnullOwnPtr is perfect as the return type of functions that never need to
return nullptr.
It's also useful as an argument type to encode the fact that the argument
must not be nullptr.
The make<Foo>() helper is changed to return NonnullOwnPtr<Foo>.
Note: You can move() out of a NonnullOwnPtr, and after that the object is
in an invalid state. Internally it will be a nullptr at this point, so we'll
still catch misuse, but the only thing that should be done in this state
is running the destructor. I've used consumable annotations to generate some
warnings when using a NonnullOwnPtr after moving from it, but these only
work when compiling with clang, so be aware of that.
