remove Clone trait implementation and use #[derive(Clone)]

[srinivasreddy]

No description provided.

[rust-highfive]

r? @brson

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[brson]

@bors r+ rollup. Thanks!

[bors]

📌 Commit 6a4c97b has been approved by brson

[eefriedman]

Hang on, are you sure this is right? I thought the reason these were derived by hand is that derive(Clone) doesn't use the right bounds; as far as I know that hasn't been fixed.

[durka]

@eefriedman is correct -- this adds T: Clone bounds to the Clone impls that were not there before.

[apasel422]

@bors r-

[srinivasreddy]

I want to implement this correct. Pointers please.

[durka]

@eddyb had thoughts about fixing this situation by elaborating trait bounds before the privacy checks. The problem is that #[derive(Clone)] needs to bound the impl by all the fields implementing Clone. But currently it can't simply list all the field types in the where clause, because it might get a "private type in public interface". So it goes with a sometimes-too-liberal strategy of bounding all type parameters. See #31518 and #33769.

[alexcrichton]

Yeah this is implemented correctly as-is to avoid the extra Clone bound on type parameters. There isn't really a "more correct" way to do this because this is indeed the "correct way to do this". As a result I'm gonna close this, but thanks for the PR!

[durka]

Well, a more correct way would be making the derived impls better. But that
can't be done without compiler support in some way.

On Tue, Jun 7, 2016 at 1:54 AM, Alex Crichton notifications@github.com
wrote:

Yeah this is implemented correctly as-is to avoid the extra Clone bound
on type parameters. There isn't really a "more correct" way to do this
because this is indeed the "correct way to do this". As a result I'm gonna
close this, but thanks for the PR!

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