Rustc hangs indefinitely when a dependent crate recursively exports one of its modules

[koute]

If you do this in a lib.rs in crate a:

pub mod module;

and then you do this in a module.rs in the same crate:

pub use module;

and then you use the crate a in a crate b then rustc will hang indefinitely during the compilation.

Steps to reproduce

cargo new a
cargo new --bin b

echo 'pub mod module;' > a/src/lib.rs
echo 'pub use module;' > a/src/module.rs

echo '[dependencies.a]' >> b/Cargo.toml
echo 'path = "../a"' >> b/Cargo.toml
echo 'extern crate a;' >> b/src/main.rs
echo 'struct Instance { x: a::A }' >> b/src/main.rs

cd b
cargo build

Meta

rustc 1.10.0-nightly (179539f 2016-05-20)
host: x86_64-unknown-linux-gnu

[jseyfried]

cc me

[aochagavia]

Reproduced on i686-pc-windows-gnu, with rustc 1.11.0-nightly (ab0b874 2016-06-13).

It may be interesting to see the output of cargo rustc -- -Ztime-passes:

time: 0.000; rss: 26MB  parsing
time: 0.000; rss: 26MB  configuration 1
time: 0.000; rss: 26MB  recursion limit
time: 0.000; rss: 26MB  crate injection
time: 0.000; rss: 26MB  plugin loading
time: 0.000; rss: 26MB  plugin registration
time: 0.045; rss: 55MB  expansion
time: 0.000; rss: 55MB  gated configuration checking
time: 0.000; rss: 55MB  maybe building test harness
time: 0.000; rss: 55MB  checking for inline asm in case the target doesn't support it
time: 0.000; rss: 55MB  complete gated feature checking
time: 0.000; rss: 55MB  assigning node ids
time: 0.000; rss: 55MB  collecting defs
time: 0.010; rss: 55MB  external crate/lib resolution
time: 0.000; rss: 55MB  early lint checks
time: 0.000; rss: 55MB  AST validation
^C

It seems that it goes wrong in name resolution, which is the step after AST validation.

[jseyfried]

I fixed this in #34542.