Duplicate Errors

[reem]

Often when I build projects with many dependencies using cargo, I end up with stuff like:

       Fresh phantom v0.0.0 (https://github.com/reem/rust-phantom.git#deb5acfe)
       Fresh encoding v0.1.0 (https://github.com/lifthrasiir/rust-encoding#7e7950dd)
       Fresh error v0.0.0 (https://github.com/reem/rust-error.git#95c6524e)
       Fresh openssl v0.0.0 (https://github.com/sfackler/rust-openssl.git#07f12370)
       Fresh url v0.1.0 (https://github.com/servo/rust-url#23fb9ec2)
       Fresh typemap v0.0.0 (https://github.com/reem/rust-typemap.git#29b2a4c5)
       Fresh http v0.1.0-pre (https://github.com/chris-morgan/rust-http.git#b7f2fe74)
       Fresh plugin v0.0.0 (https://github.com/reem/rust-plugin.git#3f2a70b1)
       Fresh content-type v0.1.0 (https://github.com/reem/rust-http-content-type.git#3a1eb53f)
       Fresh iron v0.0.1 (https://github.com/iron/iron.git#d41fff63)
   Compiling persistent v0.1.0 (file:///Users/Jonathan/hackreactor/iron-middleware/persistent)
src/lib.rs:75:9: 75:59 error: expected typemap::Assoc<alloc::arc::Arc<sync::lock::Mutex<D>>>, but found typemap::Assoc<alloc::arc::Arc<D>> (expected struct sync::lock::Mutex but found type parameter) [E0095]
src/lib.rs:75         req.extensions.find::<Read<P, D>, Arc<Mutex<D>>>()
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/lib.rs:75:9: 75:59 error: expected typemap::Assoc<alloc::arc::Arc<sync::lock::Mutex<D>>>, but found typemap::Assoc<alloc::arc::Arc<D>> (expected struct sync::lock::Mutex but found type parameter) [E0095]
src/lib.rs:75         req.extensions.find::<Read<P, D>, Arc<Mutex<D>>>()
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/lib.rs:75:9: 75:59 error: expected typemap::Assoc<alloc::arc::Arc<sync::lock::Mutex<D>>>, but found typemap::Assoc<alloc::arc::Arc<D>> (expected struct sync::lock::Mutex but found type parameter) [E0095]
src/lib.rs:75         req.extensions.find::<Read<P, D>, Arc<Mutex<D>>>()
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/lib.rs:75:9: 75:59 error: expected typemap::Assoc<alloc::arc::Arc<sync::lock::Mutex<D>>>, but found typemap::Assoc<alloc::arc::Arc<D>> (expected struct sync::lock::Mutex but found type parameter) [E0095]

Where an error is displayed many times. This is weird.

[alexcrichton]

I can't seem to reproduce this locally, do you have a repo that I could try this out on? It would preferably have a Cargo.lock checked in as well.

[reem]

It happens intermittently, I'll save the next time it happens and update this issue.

[reem]

@alexcrichton I've come across this error again and uploaded a test case here: https://github.com/reem/cargo-double-error It even includes a Cargo.lock, even though it has no deps.

That consistently gives this error message (note the double output for the error on L#33):

src/lib.rs:33:5: 33:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for fn(uint) -> uint
src/lib.rs:33     replace_map(b, double);
                  ^~~~~~~~~~~
src/lib.rs:33:5: 33:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for fn(uint) -> uint
src/lib.rs:33     replace_map(b, double);
                  ^~~~~~~~~~~
src/lib.rs:36:5: 36:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for closure
src/lib.rs:36     replace_map(b, |&mut: x: uint| x * 2);
                  ^~~~~~~~~~~
src/lib.rs:39:5: 39:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for closure
src/lib.rs:39     replace_map(b, |&: x: uint| x * 2);

I think this might be a rustc error, but I'm not sure.

[alexcrichton]

This looks to be an error in rustc itself:

$ rustc --test src/lib.rs 
src/lib.rs:33:5: 33:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for fn(uint) -> uint
src/lib.rs:33     replace_map(b, double);
                  ^~~~~~~~~~~
src/lib.rs:33:5: 33:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for fn(uint) -> uint
src/lib.rs:33     replace_map(b, double);
                  ^~~~~~~~~~~
src/lib.rs:36:5: 36:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for closure
src/lib.rs:36     replace_map(b, |&mut: x: uint| x * 2);
                  ^~~~~~~~~~~
src/lib.rs:39:5: 39:16 error: failed to find an implementation of trait core::ops::FnOnce<(uint),uint> for closure
src/lib.rs:39     replace_map(b, |&: x: uint| x * 2);
                  ^~~~~~~~~~~
error: aborting due to 4 previous errors

Would you mind opening a bug in rust-lang/rust?

[reem]

Done. rust-lang/rust#16966

[alexcrichton]

Thanks!