Disables Typedef.toString()

[denizzzka]

It is need to avoid silently conversion of Typedef struct to string by std.conv.to and to prohibit string type payload leakage.

Discussion:
https://forum.dlang.org/post/kjzayldqnixehfprgslc@forum.dlang.org

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[MetaLang]

Sorry, I think I caused a misunderstanding. We do not want to add an @disable'd toString method for Typedef, but add a toString method that just delegates to the wrapped value.

Check out std.typecons.Nullable's various overloads for inspiration:
https://github.com/dlang/phobos/blob/master/std/typecons.d#L2458

[denizzzka]

but add a toString method that just delegates to the wrapped value.

But this will make an exception for wrapped string types - it will be converted by conv.to!string unintentionally

[denizzzka]

@MetaLang You are right. Calling conv.to function is always a conscious action, and an unnoticed leak of a string isn't possible here.