Resolve const

[shoheikuni]

Hi. As well as JonathanHiggs in #54, I have a need to resolve const T types.

I tried his code and it allowed me to resolve an constructor argument of std::shared_ptr<const T>, but I couldn't compile simply container->resolve<const T>().

The necessary behavior is that a std::shared_ptr<T> is internally created when const T is required to resolve, since std::shared_ptr<T> is convertible to std::shared_ptr<const T>.
I've fixed some lines in ComponentContext::tryToRegisterType() to register std::remove_const_t<T> instead of T itself.

I hope I didn't make a mistake nor misunderstanding.

Thanks.

[JonathanHiggs]

@shoheikuni My question with this approach vs #54 is whether a registration of const T would then be resolvable as non-const which might be counter intuitive and break any intended immutability

[shoheikuni]

@JonathanHiggs Hi. My proposal is just for resolving const T when T is registered.
You can't register const T in my approach (and in the original codebase as well), so you don't need to concern about breaking immutability.
That is:

        ContainerBuilder builder;
        builder.registerType<Foo>(); // If you register Foo,
        auto container = builder.build();
        auto foo = container->resolve<Foo>(); // then you can resolve Foo
        auto cfoo = container->resolve<const Foo>(); // and const Foo.

        //builder.registerType<const Foo>(); // But you can't do this.

My proposal would not be enough If someone really wanted to register const T, but I'm not sure of such a need.