Add warn(unreachable_pub) to rustc_lint.

compiler/rustc_lint/src/late.rs

@@ -47,7 +47,7 @@ macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
 
 /// Implements the AST traversal for late lint passes. `T` provides the
 /// `check_*` methods.
-pub struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
+struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
     context: LateContext<'tcx>,
     pass: T,
 }