From 0728a0325dadb9a9d5a2469f5eab919464693508 Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Mon, 23 Dec 2024 14:54:12 +0100
Subject: [PATCH] disallow opaque types with regions in closures

---
 compiler/rustc_borrowck/src/nll.rs                   |  6 +++++-
 .../rustc_borrowck/src/region_infer/opaque_types.rs  | 12 ++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index abe27555b1864..f0111e75e4ad2 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -179,7 +179,11 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         infcx.set_tainted_by_errors(guar);
     }
 
-    let remapped_opaque_tys = regioncx.infer_opaque_types(infcx, opaque_type_values);
+    let remapped_opaque_tys = regioncx.infer_opaque_types(
+        infcx,
+        infcx.tcx.is_typeck_child(body.source.def_id()),
+        opaque_type_values,
+    );
 
     NllOutput {
         regioncx,
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 3e16a3ca157d2..b34a4272fcbd0 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -65,6 +65,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn infer_opaque_types(
         &self,
         infcx: &InferCtxt<'tcx>,
+        is_typeck_child: bool,
         opaque_ty_decls: FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
     ) -> FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>> {
         let mut result: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>> = FxIndexMap::default();
@@ -73,6 +74,17 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         for (opaque_type_key, concrete_type) in opaque_ty_decls {
             debug!(?opaque_type_key, ?concrete_type);
+            if is_typeck_child && opaque_type_key.args.iter().any(|arg| arg.as_region().is_some()) {
+                let guar = infcx.dcx().span_err(
+                    concrete_type.span,
+                    "defining of opaque type in closure involving regions",
+                );
+                result.insert(opaque_type_key.def_id, OpaqueHiddenType {
+                    span: concrete_type.span,
+                    ty: Ty::new_error(infcx.tcx, guar),
+                });
+                continue;
+            }
 
             let mut arg_regions: Vec<(ty::RegionVid, ty::Region<'_>)> =
                 vec![(self.universal_regions().fr_static, infcx.tcx.lifetimes.re_static)];