From 08c8caa5244b91ab7bda3bbc383f66ae07f3cc93 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Wed, 18 Oct 2023 09:33:57 +0000
Subject: [PATCH] convert all named regions in opaque types to nll vars

Do it in typeck before entering region inference routines
particularly because we will no longer be able to convert placeholders.
---
 compiler/rustc_borrowck/src/type_check/mod.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index a206aac0467..b72dccb2ebd 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -229,6 +229,22 @@ pub(crate) fn type_check<'mir, 'tcx>(
                 );
             }
 
+            // Convert all regions to nll vars.
+            let (opaque_type_key, hidden_type) =
+                infcx.tcx.fold_regions((opaque_type_key, hidden_type), |region, _| {
+                    match region.kind() {
+                        ty::ReVar(_) => region,
+                        ty::RePlaceholder(placeholder) => checker
+                            .borrowck_context
+                            .constraints
+                            .placeholder_region(infcx, placeholder),
+                        _ => ty::Region::new_var(
+                            infcx.tcx,
+                            checker.borrowck_context.universal_regions.to_region_vid(region),
+                        ),
+                    }
+                });
+
             (opaque_type_key, hidden_type)
         })
         .collect();