From 9a1c5eb5b385adb3cd04af0049cbf5c225cefdc3 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sat, 21 Dec 2024 17:05:40 +0000
Subject: Begin to implement type system layer of unsafe binders

---
 .../rustc_hir_analysis/src/coherence/inherent_impls.rs     |  3 ++-
 compiler/rustc_hir_analysis/src/coherence/orphan.rs        |  3 ++-
 compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs     | 14 +++++++-------
 compiler/rustc_hir_analysis/src/variance/constraints.rs    |  5 +++++
 4 files changed, 16 insertions(+), 9 deletions(-)

(limited to 'compiler/rustc_hir_analysis/src')

diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index 8f6f5b5f222..a86dede48bf 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -178,7 +178,8 @@ impl<'tcx> InherentCollect<'tcx> {
             | ty::Ref(..)
             | ty::Never
             | ty::FnPtr(..)
-            | ty::Tuple(..) => self.check_primitive_impl(id, self_ty),
+            | ty::Tuple(..)
+            | ty::UnsafeBinder(_) => self.check_primitive_impl(id, self_ty),
             ty::Alias(ty::Projection | ty::Inherent | ty::Opaque, _) | ty::Param(_) => {
                 Err(self.tcx.dcx().emit_err(errors::InherentNominal { span: item_span }))
             }
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index eca85c22a40..7d651155781 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -225,7 +225,8 @@ pub(crate) fn orphan_check_impl(
             | ty::FnDef(..)
             | ty::FnPtr(..)
             | ty::Never
-            | ty::Tuple(..) => (LocalImpl::Allow, NonlocalImpl::DisallowOther),
+            | ty::Tuple(..)
+            | ty::UnsafeBinder(_) => (LocalImpl::Allow, NonlocalImpl::DisallowOther),
 
             ty::Closure(..)
             | ty::CoroutineClosure(..)
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index b56222763d0..2154568c512 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -2318,13 +2318,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     self.lower_fn_ty(hir_ty.hir_id, bf.safety, bf.abi, bf.decl, None, Some(hir_ty)),
                 )
             }
-            hir::TyKind::UnsafeBinder(_binder) => {
-                let guar = self
-                    .dcx()
-                    .struct_span_err(hir_ty.span, "unsafe binders are not yet implemented")
-                    .emit();
-                Ty::new_error(tcx, guar)
-            }
+            hir::TyKind::UnsafeBinder(binder) => Ty::new_unsafe_binder(
+                tcx,
+                ty::Binder::bind_with_vars(
+                    self.lower_ty(binder.inner_ty),
+                    tcx.late_bound_vars(hir_ty.hir_id),
+                ),
+            ),
             hir::TyKind::TraitObject(bounds, lifetime, repr) => {
                 if let Some(guar) = self.prohibit_or_lint_bare_trait_object_ty(hir_ty) {
                     // Don't continue with type analysis if the `dyn` keyword is missing
diff --git a/compiler/rustc_hir_analysis/src/variance/constraints.rs b/compiler/rustc_hir_analysis/src/variance/constraints.rs
index 415b23d812b..e954d2b9ea4 100644
--- a/compiler/rustc_hir_analysis/src/variance/constraints.rs
+++ b/compiler/rustc_hir_analysis/src/variance/constraints.rs
@@ -322,6 +322,11 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 self.add_constraints_from_sig(current, sig_tys.with(hdr), variance);
             }
 
+            ty::UnsafeBinder(ty) => {
+                // FIXME(unsafe_binders): This is covariant, right?
+                self.add_constraints_from_ty(current, ty.skip_binder(), variance);
+            }
+
             ty::Error(_) => {
                 // we encounter this when walking the trait references for object
                 // types, where we use Error as the Self type
-- 
cgit 1.4.1-3-g733a5