Properly analyze captures from unsafe binders

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -13,6 +13,7 @@ use hir::Expr;
 use hir::def::DefKind;
 use hir::pat_util::EnumerateAndAdjustIterator as _;
 use rustc_abi::{FIRST_VARIANT, FieldIdx, VariantIdx};
+use rustc_ast::UnsafeBinderCastKind;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir::def::{CtorOf, Res};
 use rustc_hir::def_id::LocalDefId;
@@ -1393,10 +1394,18 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 self.cat_res(expr.hir_id, expr.span, expr_ty, res)
             }
 
-            // both type ascription and unsafe binder casts don't affect
-            // the place-ness of the subexpression.
+            // type ascription doesn't affect the place-ness of the subexpression.
             hir::ExprKind::Type(e, _) => self.cat_expr(e),
-            hir::ExprKind::UnsafeBinderCast(_, e, _) => self.cat_expr(e),
+
+            hir::ExprKind::UnsafeBinderCast(UnsafeBinderCastKind::Unwrap, e, _) => {
+                let base = self.cat_expr(e)?;
+                Ok(self.cat_projection(
+                    expr.hir_id,
+                    base,
+                    expr_ty,
+                    ProjectionKind::UnwrapUnsafeBinder,
+                ))
+            }
 
             hir::ExprKind::AddrOf(..)
             | hir::ExprKind::Call(..)
@@ -1427,6 +1436,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
             | hir::ExprKind::Repeat(..)
             | hir::ExprKind::InlineAsm(..)
             | hir::ExprKind::OffsetOf(..)
+            | hir::ExprKind::UnsafeBinderCast(UnsafeBinderCastKind::Wrap, ..)
             | hir::ExprKind::Err(_) => Ok(self.cat_rvalue(expr.hir_id, expr_ty)),
         }
     }

compiler/rustc_hir_typeck/src/upvar.rs

@@ -902,7 +902,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 fn is_field<'a>(p: &&Projection<'a>) -> bool {
                     match p.kind {
                         ProjectionKind::Field(_, _) => true,
-                        ProjectionKind::Deref | ProjectionKind::OpaqueCast => false,
+                        ProjectionKind::Deref
+                        | ProjectionKind::OpaqueCast
+                        | ProjectionKind::UnwrapUnsafeBinder => false,
                         p @ (ProjectionKind::Subslice | ProjectionKind::Index) => {
                             bug!("ProjectionKind {:?} was unexpected", p)
                         }
@@ -2197,7 +2199,8 @@ fn restrict_capture_precision(
             }
             ProjectionKind::Deref => {}
             ProjectionKind::OpaqueCast => {}
-            ProjectionKind::Field(..) => {} // ignore
+            ProjectionKind::Field(..) => {}
+            ProjectionKind::UnwrapUnsafeBinder => {}
         }
     }
 
@@ -2268,6 +2271,7 @@ fn construct_place_string<'tcx>(tcx: TyCtxt<'_>, place: &Place<'tcx>) -> String
             ProjectionKind::Index => String::from("Index"),
             ProjectionKind::Subslice => String::from("Subslice"),
             ProjectionKind::OpaqueCast => String::from("OpaqueCast"),
+            ProjectionKind::UnwrapUnsafeBinder => String::from("UnwrapUnsafeBinder"),
         };
         if i != 0 {
             projections_str.push(',');

compiler/rustc_middle/src/hir/place.rs

@@ -43,6 +43,9 @@ pub enum ProjectionKind {
     ///
     /// This is unused if `-Znext-solver` is enabled.
     OpaqueCast,
+
+    /// `unwrap_binder!(expr)`
+    UnwrapUnsafeBinder,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]

compiler/rustc_mir_build/src/builder/expr/as_place.rs

@@ -240,6 +240,9 @@ fn strip_prefix<'tcx>(
             HirProjectionKind::OpaqueCast => {
                 assert_matches!(iter.next(), Some(ProjectionElem::OpaqueCast(..)));
             }
+            HirProjectionKind::UnwrapUnsafeBinder => {
+                assert_matches!(iter.next(), Some(ProjectionElem::UnwrapUnsafeBinder(..)));
+            }
             HirProjectionKind::Index | HirProjectionKind::Subslice => {
                 bug!("unexpected projection kind: {:?}", projection);
             }

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -1220,6 +1220,9 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 HirProjectionKind::OpaqueCast => {
                     ExprKind::Use { source: self.thir.exprs.push(captured_place_expr) }
                 }
+                HirProjectionKind::UnwrapUnsafeBinder => ExprKind::PlaceUnwrapUnsafeBinder {
+                    source: self.thir.exprs.push(captured_place_expr),
+                },
                 HirProjectionKind::Index | HirProjectionKind::Subslice => {
                     // We don't capture these projections, so we can ignore them here
                     continue;

src/tools/clippy/clippy_utils/src/sugg.rs

@@ -941,6 +941,8 @@ impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
                         ProjectionKind::Subslice |
                         // Doesn't have surface syntax. Only occurs in patterns.
                         ProjectionKind::OpaqueCast => (),
+                        // Only occurs in closure captures.
+                        ProjectionKind::UnwrapUnsafeBinder => (),
                         ProjectionKind::Deref => {
                             // Explicit derefs are typically handled later on, but
                             // some items do not need explicit deref, such as array accesses,

tests/ui/unsafe-binders/cat-projection.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+
+#![feature(unsafe_binders)]
+#![allow(incomplete_features)]
+
+use std::unsafe_binder::unwrap_binder;
+
+#[derive(Copy, Clone)]
+pub struct S([usize; 8]);
+
+// Regression test for <https://github.com/rust-lang/rust/issues/141418>.
+pub fn by_value(x: unsafe<'a> S) -> usize {
+    unsafe { (|| unwrap_binder!(x).0[0])() }
+}
+
+// Regression test for <https://github.com/rust-lang/rust/issues/141417>.
+pub fn by_ref(x: unsafe<'a> &'a S) -> usize {
+    unsafe { (|| unwrap_binder!(x).0[0])() }
+}
+
+fn main() {}