The `Default` trait is not implemented for the `*mut T` type.

[gtors]

In my opinion, the default value should be ptr::null_mut(). Are there any reasons not implement this trait?

[Others]

I disagree with this. There is no reason to encourage the bad practice of using null pointers. It's better to leave this as-is.

[dtolnay]

Generally I prefer for code manipulating pointers to be explicit rather than implicit, so I think implementing Default would require some more motivation and discussion of the tradeoffs and alternatives. This would be a better fit for the RFC process if anyone feels strongly enough to lead that.