Fix rustc_pass_by_value.

compiler/rustc_hir/src/hir.rs

@@ -132,7 +132,7 @@ impl LifetimeName {
 
 impl fmt::Display for Lifetime {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.ident.fmt(f)
+        if self.ident.name != kw::Empty { self.ident.name.fmt(f) } else { "'_".fmt(f) }
     }
 }
 

compiler/rustc_lint/src/pass_by_value.rs

@@ -78,7 +78,7 @@ fn gen_args(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> String {
             .args
             .iter()
             .map(|arg| match arg {
-                GenericArg::Lifetime(lt) => lt.ident.to_string(),
+                GenericArg::Lifetime(lt) => lt.to_string(),
                 GenericArg::Type(ty) => {
                     cx.tcx.sess.source_map().span_to_snippet(ty.span).unwrap_or_else(|_| "_".into())
                 }