Building a binary crate complains about multiple "main" functions

[ianh]

Create main.rs:

fn main() { }

main.rc:

mod main;

Then run:

$ rustc main.rc
main.rs:1:0: 1:13 error: multiple 'main' functions
main.rs:1 fn main() { }
          ^~~~~~~~~~~~~

My rustc was built from git commit 473030.

[ianh]

Looking at debug output, rust appears to see main and main::main as two functions.

[brson]

When Rust sees a .rs file with the same name as a .rc file it automatically builds it as the top level module of the crate, so if you also add 'mod main' it will include the contents of 'main.rs' a second time.

This error happens a lot so this behavior is going to change in #2176