use std::*; makes fail! fail

[chris-morgan]

Minimal test case:

use std::*;
fn main() {
    fail!("");
}

rustc output:

<core-macros>:45:12: 45:48 error: unresolved import: could not find `sys` in `std::std`.
<core-macros>:45             ::std::sys::FailWithCause::fail_with($msg, file!(), line!())
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<core-macros>:40:4: 50:5 note: in expansion of fail!
x.rs:3:1: 3:11 note: expansion site
<core-macros>:45:12: 45:48 error: use of undeclared module `::std::sys::FailWithCause`
<core-macros>:45             ::std::sys::FailWithCause::fail_with($msg, file!(), line!())
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<core-macros>:40:4: 50:5 note: in expansion of fail!
x.rs:3:1: 3:11 note: expansion site
<core-macros>:45:12: 45:48 error: unresolved name `std::sys::FailWithCause::fail_with`.
<core-macros>:45             ::std::sys::FailWithCause::fail_with($msg, file!(), line!())
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<core-macros>:40:4: 50:5 note: in expansion of fail!
x.rs:3:1: 3:11 note: expansion site
error: aborting due to 3 previous errors

Rust 0.7, Ubuntu 13.04, 64-bit.

[brson]

Funny. This is because std exports an inner module called std that shadows std.

[brson]

There are probably other lurking bugs due to this.

[thestinger]

This evil inner module is still around. We couls probably just special case the macro injection via an attribute like #[module_is_std];.

[alexcrichton]

This could probably use a similar fix as #8242, something at the top of the file which says that the path to libstd is.

[huonw]

Fixed by the privacy changes that meant that std module in std can be private. This works:

use std::*;
fn main() {
    io::println("ok");
    fail!()
}

Flagging as needstest.