Rustc fails to compile code with "source trait is inaccessible", when the source trait is re-exported to be public.

[TyOverby]

I have a module structure that looks like this:

lib.rs
glyph_packer/
   mod.rs
   buffer2d.rs
rasterize
    mod.rs

The glyph_packer module publicly re-exports a Buffer2d trait from the buffer2d module, which is then used by rasterize/mod.rs.

However, when I attempt to implement the Buffer2d trait, I get this error:

$ rustc -V
rustc 1.8.0-nightly (3623797eb 2016-02-07)
$ cargo build
   Compiling font-atlas v0.1.2 (file:///C:/Users/Ty/workspace/rust/font-atlas)
src\rasterize/mod.rs:59:29: 59:41 error: source trait is inaccessible
src\rasterize/mod.rs:59         self.bytes.get((x + self.width() * y) as usize).cloned()
                                                    ^~~~~~~~~~~~
src\rasterize/mod.rs:59:29: 59:41 note: module `buffer2d` is private
src\rasterize/mod.rs:59         self.bytes.get((x + self.width() * y) as usize).cloned()
                                                    ^~~~~~~~~~~~
src\rasterize/mod.rs:63:17: 63:29 error: source trait is inaccessible
src\rasterize/mod.rs:63         let w = self.width();
                                        ^~~~~~~~~~~~
src\rasterize/mod.rs:63:17: 63:29 note: module `buffer2d` is private
src\rasterize/mod.rs:63         let w = self.width();
                                        ^~~~~~~~~~~~
src\rasterize/mod.rs:73:17: 73:29 error: source trait is inaccessible
src\rasterize/mod.rs:73         assert!(self.width() <= width && self.height() <= height,
                                        ^~~~~~~~~~~~
src\rasterize/mod.rs:73:9: 74:55 note: in this expansion of assert! (defined in <std macros>)
src\rasterize/mod.rs:73:17: 73:29 note: module `buffer2d` is private
src\rasterize/mod.rs:73         assert!(self.width() <= width && self.height() <= height,
                                        ^~~~~~~~~~~~
src\rasterize/mod.rs:73:9: 74:55 note: in this expansion of assert! (defined in <std macros>)
src\rasterize/mod.rs:73:42: 73:55 error: source trait is inaccessible
src\rasterize/mod.rs:73         assert!(self.width() <= width && self.height() <= height,
                                                                 ^~~~~~~~~~~~~
src\rasterize/mod.rs:73:9: 74:55 note: in this expansion of assert! (defined in <std macros>)
src\rasterize/mod.rs:73:42: 73:55 note: module `buffer2d` is private
src\rasterize/mod.rs:73         assert!(self.width() <= width && self.height() <= height,
                                                                 ^~~~~~~~~~~~~
src\rasterize/mod.rs:73:9: 74:55 note: in this expansion of assert! (defined in <std macros>)
src\rasterize/mod.rs:76:9: 76:32 error: source trait is inaccessible
src\rasterize/mod.rs:76         o_new.patch(0, 0, self);
                                ^~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:76:9: 76:32 note: module `buffer2d` is private
src\rasterize/mod.rs:76         o_new.patch(0, 0, self);
                                ^~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:96:13: 96:45 error: source trait is inaccessible
src\rasterize/mod.rs:96             out.set(x, y, (v * 255.0) as u8);
                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:96:13: 96:45 note: module `buffer2d` is private
src\rasterize/mod.rs:96             out.set(x, y, (v * 255.0) as u8);
                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:104:9: 104:34 error: source trait is inaccessible
src\rasterize/mod.rs:104         packer.set_margin(margin);
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:104:9: 104:34 note: module `packer` is private
src\rasterize/mod.rs:104         packer.set_margin(margin);
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:106:13: 106:64 error: source trait is inaccessible
src\rasterize/mod.rs:106             packer.pack_resize(&c, |(ow, oh)| (ow * 2, oh * 2));
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:106:13: 106:64 note: module `packer` is private
src\rasterize/mod.rs:106             packer.pack_resize(&c, |(ow, oh)| (ow * 2, oh * 2));
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:108:9: 108:26 error: source trait is inaccessible
src\rasterize/mod.rs:108         packer.into_buf()
                                 ^~~~~~~~~~~~~~~~~
src\rasterize/mod.rs:108:9: 108:26 note: module `packer` is private
src\rasterize/mod.rs:108         packer.into_buf()
                                 ^~~~~~~~~~~~~~~~~
error: aborting due to 9 previous errors
Could not compile `font-atlas`.

By making the glyph_packer module pub mod buffer2d; pub use buffer2d::Buffer2d; instead of just mod buffer2d; pub use buffer2d::Buffer2d; the error goes away.

[TyOverby]

Repro repo: https://github.com/TyOverby/font-atlas/tree/3d677b54576ea745ecf84e9a39c82b3ed42d7cd7

[alexcrichton]

cc @jseyfried, @petrochenkov

[jseyfried]

This is due to #18241, which was fixed by #31920 (merged three days ago).

@TyOverby I checked that your repo compiles on the most recent nighties.

[alexcrichton]

Oh awesome, thanks @jseyfried!

[TyOverby]

Thanks @jseyfried!