From edfca5fe9c7b6c12a9d48ea2dffd6fffff8501a4 Mon Sep 17 00:00:00 2001
From: Donough Liu <ldm2993593805@163.com>
Date: Mon, 27 Apr 2020 01:41:38 +0800
Subject: [PATCH] Move branch point upwards to avoid unnecessary mk_ptr()

---
 src/librustc_typeck/check/coercion.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs
index 3d665123f676..c1a3ff518b33 100644
--- a/src/librustc_typeck/check/coercion.rs
+++ b/src/librustc_typeck/check/coercion.rs
@@ -771,10 +771,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             ty::RawPtr(mt) => (false, mt),
             _ => return self.unify_and(a, b, identity),
         };
+        coerce_mutbls(mt_a.mutbl, mutbl_b)?;
 
         // Check that the types which they point at are compatible.
         let a_unsafe = self.tcx.mk_ptr(ty::TypeAndMut { mutbl: mutbl_b, ty: mt_a.ty });
-        coerce_mutbls(mt_a.mutbl, mutbl_b)?;
         // Although references and unsafe ptrs have the same
         // representation, we still register an Adjust::DerefRef so that
         // regionck knows that the region for `a` must be valid here.