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Private variants can be publicly reexported #30055

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petrochenkov opened this issue Nov 25, 2015 · 0 comments
Closed

Private variants can be publicly reexported #30055

petrochenkov opened this issue Nov 25, 2015 · 0 comments
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A-resolve Area: Name resolution

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@petrochenkov
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This snippet compiles, but it shouldn't, because the variants V1 and V2 belong to private enums and private things can't normally be publicly reexported.

enum E1 { V1 }
enum E2 { V2 }

pub use E1::V1;
pub use E2::*;

fn main() {}

Reproduces on stable/beta/nightly.
The E1::V1 case is fixed in #29973, E2::* is not fixed is fixed in #29973 as well .
@Aatch Aatch added I-wrong A-resolve Area: Name resolution labels Nov 27, 2015
@petrochenkov petrochenkov mentioned this issue Dec 2, 2015
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bors added a commit that referenced this issue Dec 18, 2015
@bors
Auto merge of #29973 - petrochenkov:privinpub, r=nikomatsakis
ef91cdb 
Some notes:
This patch enforces the rules from [RFC 136](https://github.com/rust-lang/rfcs/blob/master/text/0136-no-privates-in-public.md) and makes "private in public" a module-level concept and not crate-level. Only `pub` annotations are used by the new algorithm, crate-level exported node set produced by `EmbargoVisitor` is not used. The error messages are tweaked accordingly and don't use the word "exported" to avoid confusing people (#29668).

The old algorithm tried to be extra smart with impls, but it mostly led to unpredictable behavior and bugs like #28325.
The new algorithm tries to be as simple as possible - an impl is considered public iff its type is public and its trait is public (if presents).
A type or trait is considered public if all its components are public, [complications](https://internals.rust-lang.org/t/limits-of-type-inference-smartness/2919) with private types leaking to other crates/modules through trait impls and type inference are deliberately ignored so far.

The new algorithm is not recursive and uses the nice new facility `Crate::visit_all_items`!

Obsolete pre-1.0 feature `visible_private_types` is removed.

This is a [breaking-change].
The two main vectors of breakage are type aliases (#28450) and impls (#28325).
I need some statistics from a crater run (cc @alexcrichton) to decide on the breakage mitigation strategy.
UPDATE: All the new errors are reported as warnings controlled by a lint `private_in_public` and lint group `future_incompatible`, but the intent is to make them hard errors eventually.

Closes #28325
Closes #28450
Closes #29524
Closes #29627
Closes #29668
Closes #30055

r? @nikomatsakis
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