Implement MIR projection for unsafe binder cast

compiler-errors · compiler-errors · commit 59ed54f9aef4 · 2024-12-14T20:27:46.000Z
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
@@ -1662,7 +1662,7 @@ impl GenBlockKind {
 }
 
 /// Whether we're unwrapping or wrapping an unsafe binder
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 #[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum UnsafeBinderCastKind {
     // e.g. `&i32` -> `unsafe<'a> &'a i32`
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -3977,7 +3977,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         ProjectionElem::ConstantIndex { .. }
                         | ProjectionElem::Subslice { .. }
                         | ProjectionElem::Subtype(_)
-                        | ProjectionElem::Index(_) => kind,
+                        | ProjectionElem::Index(_)
+                        | ProjectionElem::UnsafeBinderCast(..) => kind,
                     },
                     place_ty.projection_ty(tcx, elem),
                 )
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -244,6 +244,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 ProjectionElem::Downcast(..) => (),
                 ProjectionElem::OpaqueCast(..) => (),
                 ProjectionElem::Subtype(..) => (),
+                ProjectionElem::UnsafeBinderCast(..) => (),
                 ProjectionElem::Field(field, _ty) => {
                     // FIXME(project-rfc_2229#36): print capture precisely here.
                     if let Some(field) = self.is_upvar_field_projection(PlaceRef {
@@ -324,9 +325,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
                 }
                 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
-                ProjectionElem::Subtype(ty) | ProjectionElem::OpaqueCast(ty) => {
-                    PlaceTy::from_ty(*ty)
-                }
+                ProjectionElem::Subtype(ty)
+                | ProjectionElem::OpaqueCast(ty)
+                | ProjectionElem::UnsafeBinderCast(_, ty) => PlaceTy::from_ty(*ty),
                 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
             },
         };
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -168,7 +168,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         | ProjectionElem::ConstantIndex { .. }
                         | ProjectionElem::OpaqueCast { .. }
                         | ProjectionElem::Subslice { .. }
-                        | ProjectionElem::Downcast(..),
+                        | ProjectionElem::Downcast(..)
+                        | ProjectionElem::UnsafeBinderCast(..),
                     ],
             } => bug!("Unexpected immutable place."),
         }
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
@@ -1716,7 +1716,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 // So it's safe to skip these.
                 ProjectionElem::OpaqueCast(_)
                 | ProjectionElem::Subtype(_)
-                | ProjectionElem::Downcast(_, _) => (),
+                | ProjectionElem::Downcast(_, _)
+                | ProjectionElem::UnsafeBinderCast(_, _) => (),
             }
 
             place_ty = place_ty.projection_ty(tcx, elem);
@@ -1944,7 +1945,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 ProjectionElem::OpaqueCast(_) |
                 ProjectionElem::ConstantIndex { .. } |
                 // assigning to P[i] requires P to be valid.
-                ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) =>
+                ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) |
+                ProjectionElem::UnsafeBinderCast(..) =>
                 // assigning to (P->variant) is okay if assigning to `P` is okay
                 //
                 // FIXME: is this true even if P is an adt with a dtor?
@@ -2330,7 +2332,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                     | ProjectionElem::Subslice { .. }
                     | ProjectionElem::Subtype(..)
                     | ProjectionElem::OpaqueCast { .. }
-                    | ProjectionElem::Downcast(..) => {
+                    | ProjectionElem::Downcast(..)
+                    | ProjectionElem::UnsafeBinderCast(..) => {
                         let upvar_field_projection = self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
                             let upvar = &self.upvars[field.index()];
diff --git a/compiler/rustc_borrowck/src/places_conflict.rs b/compiler/rustc_borrowck/src/places_conflict.rs
@@ -250,7 +250,8 @@ fn place_components_conflict<'tcx>(
                 | (ProjectionElem::Subslice { .. }, _, _)
                 | (ProjectionElem::OpaqueCast { .. }, _, _)
                 | (ProjectionElem::Subtype(_), _, _)
-                | (ProjectionElem::Downcast { .. }, _, _) => {
+                | (ProjectionElem::Downcast { .. }, _, _)
+                | (ProjectionElem::UnsafeBinderCast(..), _, _) => {
                     // Recursive case. This can still be disjoint on a
                     // further iteration if this a shallow access and
                     // there's a deref later on, e.g., a borrow
@@ -519,5 +520,9 @@ fn place_projection_conflict<'tcx>(
             pi1_elem,
             pi2_elem
         ),
+
+        (ProjectionElem::UnsafeBinderCast(..), _) => {
+            todo!()
+        }
     }
 }
diff --git a/compiler/rustc_borrowck/src/prefixes.rs b/compiler/rustc_borrowck/src/prefixes.rs
@@ -70,7 +70,8 @@ impl<'tcx> Iterator for Prefixes<'tcx> {
                         | ProjectionElem::Subslice { .. }
                         | ProjectionElem::OpaqueCast { .. }
                         | ProjectionElem::ConstantIndex { .. }
-                        | ProjectionElem::Index(_) => {
+                        | ProjectionElem::Index(_)
+                        | ProjectionElem::UnsafeBinderCast(..) => {
                             cursor = cursor_base;
                         }
                         ProjectionElem::Subtype(..) => {
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -719,6 +719,48 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                     .unwrap();
                 PlaceTy::from_ty(ty)
             }
+            ProjectionElem::UnsafeBinderCast(kind, ty) => match kind {
+                hir::UnsafeBinderCastKind::Wrap => {
+                    let ty::UnsafeBinder(binder_ty) = *ty.kind() else {
+                        bug!();
+                    };
+                    let expected_ty = self.cx.infcx.instantiate_binder_with_fresh_vars(
+                        self.body().source_info(location).span,
+                        BoundRegionConversionTime::HigherRankedType,
+                        binder_ty.into(),
+                    );
+                    self.cx
+                        .relate_types(
+                            expected_ty,
+                            self.get_ambient_variance(context),
+                            base_ty,
+                            location.to_locations(),
+                            ConstraintCategory::TypeAnnotation,
+                        )
+                        .unwrap();
+                    PlaceTy::from_ty(ty)
+                }
+                hir::UnsafeBinderCastKind::Unwrap => {
+                    let ty::UnsafeBinder(binder_ty) = *base_ty.kind() else {
+                        bug!();
+                    };
+                    let found_ty = self.cx.infcx.instantiate_binder_with_fresh_vars(
+                        self.body().source_info(location).span,
+                        BoundRegionConversionTime::HigherRankedType,
+                        binder_ty.into(),
+                    );
+                    self.cx
+                        .relate_types(
+                            ty,
+                            self.get_ambient_variance(context),
+                            found_ty,
+                            location.to_locations(),
+                            ConstraintCategory::TypeAnnotation,
+                        )
+                        .unwrap();
+                    PlaceTy::from_ty(ty)
+                }
+            },
         }
     }
 
@@ -2705,7 +2747,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 | ProjectionElem::OpaqueCast(..)
                 | ProjectionElem::Index(..)
                 | ProjectionElem::ConstantIndex { .. }
-                | ProjectionElem::Subslice { .. } => {
+                | ProjectionElem::Subslice { .. }
+                | ProjectionElem::UnsafeBinderCast(..) => {
                     // other field access
                 }
                 ProjectionElem::Subtype(_) => {
diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -504,6 +504,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     bug!("encountered OpaqueCast({ty}) in codegen")
                 }
                 mir::ProjectionElem::Subtype(ty) => cg_base.project_type(bx, self.monomorphize(ty)),
+                mir::ProjectionElem::UnsafeBinderCast(_, ty) => {
+                    cg_base.project_type(bx, self.monomorphize(ty))
+                }
                 mir::ProjectionElem::Index(index) => {
                     let index = &mir::Operand::Copy(mir::Place::from(index));
                     let index = self.codegen_operand(bx, index);
diff --git a/compiler/rustc_const_eval/src/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/check_consts/qualifs.rs
@@ -297,7 +297,8 @@ where
             | ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Downcast(_, _)
-            | ProjectionElem::Index(_) => {}
+            | ProjectionElem::Index(_)
+            | ProjectionElem::UnsafeBinderCast(..) => {}
         }
 
         let base_ty = place_base.ty(cx.body, cx.tcx);
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -381,6 +381,7 @@ where
             OpaqueCast(ty) => {
                 span_bug!(self.cur_span(), "OpaqueCast({ty}) encountered after borrowck")
             }
+            UnsafeBinderCast(_, target) => base.transmute(self.layout_of(target)?, self)?,
             // We don't want anything happening here, this is here as a dummy.
             Subtype(_) => base.transmute(base.layout(), self)?,
             Field(field, _) => self.project_field(base, field.index())?,
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
@@ -1286,6 +1286,14 @@ fn pre_fmt_projection(projection: &[PlaceElem<'_>], fmt: &mut Formatter<'_>) ->
             ProjectionElem::Index(_)
             | ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. } => {}
+            ProjectionElem::UnsafeBinderCast(kind, _) => match kind {
+                hir::UnsafeBinderCastKind::Wrap => {
+                    write!(fmt, "wrap_unsafe_binder!(")?;
+                }
+                rustc_ast::UnsafeBinderCastKind::Unwrap => {
+                    write!(fmt, "unwrap_unsafe_binder!(")?;
+                }
+            },
         }
     }
 
@@ -1334,6 +1342,9 @@ fn post_fmt_projection(projection: &[PlaceElem<'_>], fmt: &mut Formatter<'_>) ->
             ProjectionElem::Subslice { from, to, from_end: false } => {
                 write!(fmt, "[{from:?}..{to:?}]")?;
             }
+            ProjectionElem::UnsafeBinderCast(_, ty) => {
+                write!(fmt, "; {ty})")?;
+            }
         }
     }
 
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
@@ -62,7 +62,8 @@ impl<V, T> ProjectionElem<V, T> {
             | Self::Subtype(_)
             | Self::ConstantIndex { .. }
             | Self::Subslice { .. }
-            | Self::Downcast(_, _) => false,
+            | Self::Downcast(_, _)
+            | Self::UnsafeBinderCast(..) => false,
         }
     }
 
@@ -76,7 +77,8 @@ impl<V, T> ProjectionElem<V, T> {
             | Self::Subtype(_)
             | Self::ConstantIndex { .. }
             | Self::Subslice { .. }
-            | Self::Downcast(_, _) => true,
+            | Self::Downcast(_, _)
+            | Self::UnsafeBinderCast(..) => true,
         }
     }
 
@@ -102,6 +104,9 @@ impl<V, T> ProjectionElem<V, T> {
             | Self::Subtype(_)
             | Self::OpaqueCast(_)
             | Self::Subslice { .. } => false,
+
+            // FIXME(unsafe_binders): Figure this out.
+            Self::UnsafeBinderCast(..) => false,
         }
     }
 }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
@@ -6,8 +6,8 @@
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece, Mutability};
 use rustc_data_structures::packed::Pu128;
-use rustc_hir::CoroutineKind;
 use rustc_hir::def_id::DefId;
+use rustc_hir::{CoroutineKind, UnsafeBinderCastKind};
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_span::Span;
@@ -1211,6 +1211,8 @@ pub enum ProjectionElem<V, T> {
     /// requiring an intermediate variable.
     OpaqueCast(T),
 
+    UnsafeBinderCast(UnsafeBinderCastKind, T),
+
     /// A `Subtype(T)` projection is applied to any `StatementKind::Assign` where
     /// type of lvalue doesn't match the type of rvalue, the primary goal is making subtyping
     /// explicit during optimizations and codegen.
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
@@ -111,6 +111,11 @@ impl<'tcx> PlaceTy<'tcx> {
             ProjectionElem::Subtype(ty) => {
                 PlaceTy::from_ty(handle_opaque_cast_and_subtype(&self, ty))
             }
+
+            // FIXME(unsafe_binders): Rename `handle_opaque_cast_and_subtype` to be more general.
+            ProjectionElem::UnsafeBinderCast(_, ty) => {
+                PlaceTy::from_ty(handle_opaque_cast_and_subtype(&self, ty))
+            }
         };
         debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
         answer
diff --git a/compiler/rustc_middle/src/mir/type_foldable.rs b/compiler/rustc_middle/src/mir/type_foldable.rs
@@ -1,6 +1,7 @@
 //! `TypeFoldable` implementations for MIR types
 
 use rustc_ast::InlineAsmTemplatePiece;
+use rustc_hir::UnsafeBinderCastKind;
 use rustc_hir::def_id::LocalDefId;
 
 use super::*;
@@ -20,6 +21,7 @@ TrivialTypeTraversalImpls! {
     SwitchTargets,
     CoroutineKind,
     CoroutineSavedLocal,
+    UnsafeBinderCastKind,
 }
 
 TrivialTypeTraversalImpls! {
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
@@ -1148,6 +1148,15 @@ macro_rules! visit_place_fns {
                     self.visit_ty(&mut new_ty, TyContext::Location(location));
                     if ty != new_ty { Some(PlaceElem::Subtype(new_ty)) } else { None }
                 }
+                PlaceElem::UnsafeBinderCast(kind, ty) => {
+                    let mut new_ty = ty;
+                    self.visit_ty(&mut new_ty, TyContext::Location(location));
+                    if ty != new_ty {
+                        Some(PlaceElem::UnsafeBinderCast(kind, new_ty))
+                    } else {
+                        None
+                    }
+                }
                 PlaceElem::Deref
                 | PlaceElem::ConstantIndex { .. }
                 | PlaceElem::Subslice { .. }
@@ -1216,7 +1225,8 @@ macro_rules! visit_place_fns {
             match elem {
                 ProjectionElem::OpaqueCast(ty)
                 | ProjectionElem::Subtype(ty)
-                | ProjectionElem::Field(_, ty) => {
+                | ProjectionElem::Field(_, ty)
+                | ProjectionElem::UnsafeBinderCast(_, ty) => {
                     self.visit_ty(ty, TyContext::Location(location));
                 }
                 ProjectionElem::Index(local) => {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/build/expr/as_place.rs
@@ -105,7 +105,8 @@ fn convert_to_hir_projections_and_truncate_for_capture(
             ProjectionElem::OpaqueCast(_) | ProjectionElem::Subtype(..) => continue,
             ProjectionElem::Index(..)
             | ProjectionElem::ConstantIndex { .. }
-            | ProjectionElem::Subslice { .. } => {
+            | ProjectionElem::Subslice { .. }
+            | ProjectionElem::UnsafeBinderCast(..) => {
                 // We don't capture array-access projections.
                 // We can stop here as arrays are captured completely.
                 break;
@@ -523,20 +524,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 block.and(PlaceBuilder::from(temp))
             }
 
-            ExprKind::PlaceUnsafeBinderCast { source, kind: _ } => {
+            ExprKind::PlaceUnsafeBinderCast { source, kind } => {
                 let place_builder = unpack!(
                     block = this.expr_as_place(block, source, mutability, fake_borrow_temps,)
                 );
-                // TODO: stick on a projection elem
-                block.and(place_builder)
+                block.and(place_builder.project(PlaceElem::UnsafeBinderCast(kind, expr.ty)))
             }
-            ExprKind::ValueUnsafeBinderCast { source, kind: _ } => {
+            ExprKind::ValueUnsafeBinderCast { source, kind } => {
                 let source_expr = &this.thir[source];
                 let temp = unpack!(
                     block = this.as_temp(block, source_expr.temp_lifetime, source, mutability)
                 );
-                // TODO: stick on a projection elem
-                block.and(PlaceBuilder::from(temp))
+                block.and(
+                    PlaceBuilder::from(temp).project(PlaceElem::UnsafeBinderCast(kind, expr.ty)),
+                )
             }
 
             ExprKind::Array { .. }
@@ -729,7 +730,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     | ProjectionElem::OpaqueCast(..)
                     | ProjectionElem::Subtype(..)
                     | ProjectionElem::ConstantIndex { .. }
-                    | ProjectionElem::Subslice { .. } => (),
+                    | ProjectionElem::Subslice { .. }
+                    | ProjectionElem::UnsafeBinderCast(..) => (),
                 }
             }
         }
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs b/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
@@ -32,6 +32,9 @@ impl<'tcx> Lift for PlaceElem<'tcx> {
             }
             ProjectionElem::Downcast(a, u) => ProjectionElem::Downcast(a, u),
             ProjectionElem::Subtype(_ty) => ProjectionElem::Subtype(()),
+            ProjectionElem::UnsafeBinderCast(kind, _ty) => {
+                ProjectionElem::UnsafeBinderCast(kind, ())
+            }
         }
     }
 }
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -229,10 +229,12 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
                 // `OpaqueCast`:Only transmutes the type, so no moves there.
                 // `Downcast`  :Only changes information about a `Place` without moving.
                 // `Subtype`   :Only transmutes the type, so moves.
+                // `UnsafeBinderCast`: Only transmutes the place without moving.
                 // So it's safe to skip these.
                 ProjectionElem::OpaqueCast(_)
                 | ProjectionElem::Subtype(_)
-                | ProjectionElem::Downcast(_, _) => (),
+                | ProjectionElem::Downcast(_, _)
+                | ProjectionElem::UnsafeBinderCast(_, _) => (),
             }
             let elem_ty = PlaceTy::from_ty(place_ty).projection_ty(tcx, elem).ty;
             if !(self.filter)(elem_ty) {
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs

Original file line number	Diff line number	Diff line change
`@@ -1662,7 +1662,7 @@ impl GenBlockKind {`
`1662`	`1662`	`}`
`1663`	`1663`
`1664`	`1664`	`/// Whether we're unwrapping or wrapping an unsafe binder`
`1665`		`-#[derive(Copy, Clone, Debug, PartialEq, Eq)]`
	`1665`	`+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]`
`1666`	`1666`	`#[derive(Encodable, Decodable, HashStable_Generic)]`
`1667`	`1667`	`pub enum UnsafeBinderCastKind {`
`1668`	`1668`	// e.g. `&i32` -> `unsafe<'a> &'a i32`
Original file line number	Diff line number	Diff line change
`@@ -297,7 +297,8 @@ where`
`297`	`297`	`\| ProjectionElem::ConstantIndex { .. }`
`298`	`298`	`\| ProjectionElem::Subslice { .. }`
`299`	`299`	`\| ProjectionElem::Downcast(_, _)`
`300`		`- \| ProjectionElem::Index(_) => {}`
	`300`	`+ \| ProjectionElem::Index(_)`
	`301`	`+ \| ProjectionElem::UnsafeBinderCast(..) => {}`
`301`	`302`	`}`
`302`	`303`
`303`	`304`	`let base_ty = place_base.ty(cx.body, cx.tcx);`