From f4a3ed02439adb6b168e6979fcfef7dc2a9fc33a Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 12 Aug 2024 15:37:28 +1000
Subject: [PATCH] Avoid a `FnPtr` deconstruct-and-recreate.

---
 compiler/rustc_middle/src/ty/layout.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 55511d0833ce..f16f4baf723e 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -986,10 +986,11 @@ fn ty_and_layout_pointee_info_at(
                     safe: None,
                 })
             }
-            ty::FnPtr(sig_tys, hdr) if offset.bytes() == 0 => {
-                let fn_sig = sig_tys.with(hdr);
-                tcx.layout_of(param_env.and(Ty::new_fn_ptr(tcx, fn_sig))).ok().map(|layout| {
-                    PointeeInfo { size: layout.size, align: layout.align.abi, safe: None }
+            ty::FnPtr(..) if offset.bytes() == 0 => {
+                tcx.layout_of(param_env.and(this.ty)).ok().map(|layout| PointeeInfo {
+                    size: layout.size,
+                    align: layout.align.abi,
+                    safe: None,
                 })
             }
             ty::Ref(_, ty, mt) if offset.bytes() == 0 => {