Warn when reexporting a private extern crate

src/librustc/lib.rs

@@ -51,7 +51,7 @@ extern crate getopts;
 extern crate graphviz;
 extern crate libc;
 extern crate rbml;
-extern crate rustc_llvm;
+pub extern crate rustc_llvm as llvm;
 extern crate rustc_back;
 extern crate rustc_front;
 extern crate rustc_data_structures;
@@ -66,8 +66,6 @@ extern crate serialize as rustc_serialize; // used by deriving
 #[cfg(test)]
 extern crate test;
 
-pub use rustc_llvm as llvm;
-
 #[macro_use]
 mod macros;
 

src/librustc_resolve/resolve_imports.rs

@@ -402,14 +402,23 @@ impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
             }
 
             (_, &Success(name_binding)) if !name_binding.is_import() && directive.is_public => {
-                // Disallow reexporting private items, excepting extern crates.
+                if !name_binding.is_public() {
-                if !name_binding.is_public() && !name_binding.is_extern_crate() {
+                    if name_binding.is_extern_crate() {
+                        let msg = format!("extern crate `{}` is private, and cannot be reexported \
+                                           (error E0364), consider declaring with `pub`",
+                                           source);
+                        self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
+                                                       directive.id,
+                                                       directive.span,
+                                                       msg);
+                    } else {
                         let msg = format!("`{}` is private, and cannot be reexported", source);
                         let note_msg =
                             format!("Consider declaring type or module `{}` with `pub`", source);
                         struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
                             .span_note(directive.span, &note_msg)
                             .emit();
+                    }
                 } else if name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
                     let msg = format!("variant `{}` is private, and cannot be reexported \
                                        (error E0364), consider declaring its enum as `pub`",

src/librustc_trans/lib.rs

@@ -46,7 +46,7 @@ extern crate rustc;
 extern crate rustc_back;
 extern crate rustc_data_structures;
 extern crate rustc_front;
-extern crate rustc_llvm as llvm;
+pub extern crate rustc_llvm as llvm;
 extern crate rustc_mir;
 extern crate rustc_platform_intrinsics as intrinsics;
 extern crate serialize;

src/libstd/sys/unix/net.rs

@@ -21,7 +21,7 @@ use sys_common::net::{getsockopt, setsockopt};
 use time::Duration;
 
 pub use sys::{cvt, cvt_r};
-pub use libc as netc;
+pub extern crate libc as netc;
 
 pub type wrlen_t = size_t;
 

src/test/compile-fail/private-variant-and-crate-reexport.rs

@@ -11,6 +11,10 @@
 #![feature(rustc_attrs)]
 #![allow(dead_code)]
 
+extern crate core;
+pub use core as reexported_core; //~ WARN extern crate `core` is private, and cannot be reexported
+//~^ WARNING hard error
+
 mod m1 {
     pub use ::E::V; //~ WARN variant `V` is private, and cannot be reexported
     //~^ WARNING hard error