Make defid rustfmtable

rustc.diff

diff --git a/compiler/rustc_interface/src/callbacks.rs b/compiler/rustc_interface/src/callbacks.rs
index 7fa1a3eb0f5..6a22af30206 100644
--- a/compiler/rustc_interface/src/callbacks.rs
+++ b/compiler/rustc_interface/src/callbacks.rs
@@ -42,14 +42,14 @@ fn track_diagnostic(diagnostic: &Diagnostic) {
 /// This is a callback from librustc_hir as it cannot access the implicit state
 /// in librustc_middle otherwise.
 fn def_id_debug(def_id: rustc_hir::def_id::DefId, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    write!(f, "DefId({}:{}", def_id.krate, def_id.index.index())?;
+    write!(f, "DefId(\"{}:{}", def_id.krate, def_id.index.index())?;
     tls::with_opt(|opt_tcx| {
         if let Some(tcx) = opt_tcx {
             write!(f, " ~ {}", tcx.def_path_debug_str(def_id))?;
         }
         Ok(())
     })?;
-    write!(f, ")")
+    write!(f, "\")")
 }
 
 /// Sets up the callbacks in prior crates which we want to refer to the