'duplicate definitions' regression with winapi 0.2.5

[brson]

With rustc 1.9.0-nightly (74b886ab1 2016-03-13) I see this error building winapi 0.2.5:

C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:148:13: 150:14 error: duplicate definitions with name `item`: [E0201]
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:148             pub unsafe fn $variant(&self) -> &$fieldtype {
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:149                 ::std::mem::transmute(&self.$field)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:150             }
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\commctrl.rs:2496:1: 2496:59 note: in this expansion of UNION! (defined in C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:148:13: 150:14 help: run `rustc --explain E0201` to see a detailed explanation
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:148:13: 150:14 note: conflicting definition is here:
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:148             pub unsafe fn $variant(&self) -> &$fieldtype {
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:149                 ::std::mem::transmute(&self.$field)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:150             }
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\commctrl.rs:2503:1: 2503:59 note: in this expansion of UNION! (defined in C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:152:13: 154:14 error: duplicate definitions with name `item_mut`: [E0201]
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:152             pub unsafe fn $variantmut(&mut self) -> &mut $fieldtype {
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:153                 ::std::mem::transmute(&mut self.$field)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:154             }
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\commctrl.rs:2496:1: 2496:59 note: in this expansion of UNION! (defined in C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:152:13: 154:14 help: run `rustc --explain E0201` to see a detailed explanation
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:152:13: 154:14 note: conflicting definition is here:
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:152             pub unsafe fn $variantmut(&mut self) -> &mut $fieldtype {
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:153                 ::std::mem::transmute(&mut self.$field)
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs:154             }
C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\commctrl.rs:2503:1: 2503:59 note: in this expansion of UNION! (defined in C:\Users\brian\AppData\Local\.multirust\cargo\registry\src\github.heygears.com-88ac128001ac3a9a\winapi-0.2.5\src\macros.rs)
error: aborting due to 2 previous errors

This worked as recently as rustc 1.9.0-nightly (c9629d61c 2016-03-10).

cc @retep998 @nikomatsakis

[retep998]

Apparently this is a legitimate error in winapi that retep998/winapi-rs#267 will fix.

However, how did Rust not error about this before? The commit that added those lines was authored on Jul 30, 2015.

[alexcrichton]

This is likely due to #31925

cc @aturon, @rust-lang/lang

Also nominating (I guess for T-lang?) for some discussion, seems like a standard "let's ship a fix and continue with the course correction", however, to me.

[aturon]

Oh wow, we didn't go through a warning cycle for this change because we didn't expect the error to be hit.

Is this a significant enough problem for the ecosystem that we should switch to yield a warning for now? That's a pretty easy change to make.

[brson]

Since it's winapi, it seems prudent to switch it to a warning.

[aturon]

@alexcrichton tells me on IRC that a quick publication on winapi should address this, but if it's still not looking good by tomorrow morning I'll push up a PR to move to warning.

[retep998]

winapi = "0.2.6" has been published with a fix for this.

[aturon]

@retep998 Thanks much!

@brson Was that the only breakage you saw?

[brson]

@aturon yes

[dpc]

I think #32301 is related.

[aturon]

Update: I'm planning to land a PR changing this error to a warning shortly. At the moment, we still intend to go forward with this change (which we see as a bugfix), but will have at least one release cycle with warnings first.

[nikomatsakis]

triage: P-high