From 9f83d36edcfeabad63e95338c17942a36f072782 Mon Sep 17 00:00:00 2001
From: Bastian Kauschke <bastian_kauschke@hotmail.de>
Date: Sun, 31 May 2020 17:16:44 +0200
Subject: [PATCH] remove trivial calls to mk_const

---
 src/librustc_middle/ty/structural_impls.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/librustc_middle/ty/structural_impls.rs b/src/librustc_middle/ty/structural_impls.rs
index c6ecb08615fcf..aa47c6b70a21a 100644
--- a/src/librustc_middle/ty/structural_impls.rs
+++ b/src/librustc_middle/ty/structural_impls.rs
@@ -1019,7 +1019,11 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
         let ty = self.ty.fold_with(folder);
         let val = self.val.fold_with(folder);
-        folder.tcx().mk_const(ty::Const { ty, val })
+        if ty != self.ty || val != self.val {
+            folder.tcx().mk_const(ty::Const { ty, val })
+        } else {
+            *self
+        }
     }
 
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {