Merge from rustc

Author: RalfJung

src/diagnostics.rs

@@ -289,7 +289,7 @@ pub fn report_error<'tcx, 'mir>(
                     (None, format!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information")),
                 ],
             InvalidProgram(
-                InvalidProgramInfo::AlreadyReported(rustc_errors::ErrorGuaranteed { .. })
+                InvalidProgramInfo::AlreadyReported(_)
             ) => {
                 // This got already reported. No point in reporting it again.
                 return None;

src/lib.rs

@@ -47,7 +47,6 @@ extern crate rustc_ast;
 extern crate rustc_middle;
 extern crate rustc_const_eval;
 extern crate rustc_data_structures;
-extern crate rustc_errors;
 extern crate rustc_hir;
 extern crate rustc_index;
 extern crate rustc_session;