Implement pin-project in pattern matching for &pin mut|const T

compiler/rustc_ast/src/ast.rs

@@ -719,14 +719,14 @@ pub struct PatField {
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum ByRef {
-    Yes(Mutability),
+    Yes(Pinnedness, Mutability),
     No,
 }
 
 impl ByRef {
     #[must_use]
     pub fn cap_ref_mutability(mut self, mutbl: Mutability) -> Self {
-        if let ByRef::Yes(old_mutbl) = &mut self {
+        if let ByRef::Yes(_, old_mutbl) = &mut self {
             *old_mutbl = cmp::min(*old_mutbl, mutbl);
         }
         self
@@ -744,20 +744,33 @@ pub struct BindingMode(pub ByRef, pub Mutability);
 
 impl BindingMode {
     pub const NONE: Self = Self(ByRef::No, Mutability::Not);
-    pub const REF: Self = Self(ByRef::Yes(Mutability::Not), Mutability::Not);
+    pub const REF: Self = Self(ByRef::Yes(Pinnedness::Not, Mutability::Not), Mutability::Not);
+    pub const REF_PIN: Self =
+        Self(ByRef::Yes(Pinnedness::Pinned, Mutability::Not), Mutability::Not);
     pub const MUT: Self = Self(ByRef::No, Mutability::Mut);
-    pub const REF_MUT: Self = Self(ByRef::Yes(Mutability::Mut), Mutability::Not);
-    pub const MUT_REF: Self = Self(ByRef::Yes(Mutability::Not), Mutability::Mut);
-    pub const MUT_REF_MUT: Self = Self(ByRef::Yes(Mutability::Mut), Mutability::Mut);
+    pub const REF_MUT: Self = Self(ByRef::Yes(Pinnedness::Not, Mutability::Mut), Mutability::Not);
+    pub const REF_PIN_MUT: Self =
+        Self(ByRef::Yes(Pinnedness::Pinned, Mutability::Mut), Mutability::Not);
+    pub const MUT_REF: Self = Self(ByRef::Yes(Pinnedness::Not, Mutability::Not), Mutability::Mut);
+    pub const MUT_REF_PIN: Self =
+        Self(ByRef::Yes(Pinnedness::Pinned, Mutability::Not), Mutability::Mut);
+    pub const MUT_REF_MUT: Self =
+        Self(ByRef::Yes(Pinnedness::Not, Mutability::Mut), Mutability::Mut);
+    pub const MUT_REF_PIN_MUT: Self =
+        Self(ByRef::Yes(Pinnedness::Pinned, Mutability::Mut), Mutability::Mut);
 
     pub fn prefix_str(self) -> &'static str {
         match self {
             Self::NONE => "",
             Self::REF => "ref ",
+            Self::REF_PIN => "ref pin const ",
             Self::MUT => "mut ",
             Self::REF_MUT => "ref mut ",
+            Self::REF_PIN_MUT => "ref pin mut ",
             Self::MUT_REF => "mut ref ",
+            Self::MUT_REF_PIN => "mut ref pin ",
             Self::MUT_REF_MUT => "mut ref mut ",
+            Self::MUT_REF_PIN_MUT => "mut ref pin mut ",
         }
     }
 }

compiler/rustc_ast_ir/src/lib.rs

@@ -101,3 +101,10 @@ pub enum Pinnedness {
     Not,
     Pinned,
 }
+
+impl Pinnedness {
+    /// Return `true` if self is pinned
+    pub fn is_pinned(self) -> bool {
+        matches!(self, Self::Pinned)
+    }
+}

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1624,10 +1624,15 @@ impl<'a> State<'a> {
                 if mutbl.is_mut() {
                     self.word_nbsp("mut");
                 }
-                if let ByRef::Yes(rmutbl) = by_ref {
+                if let ByRef::Yes(pinnedness, rmutbl) = by_ref {
                     self.word_nbsp("ref");
+                    if pinnedness.is_pinned() {
+                        self.word_nbsp("pin");
+                    }
                     if rmutbl.is_mut() {
                         self.word_nbsp("mut");
+                    } else if pinnedness.is_pinned() {
+                        self.word_nbsp("const");
                     }
                 }
                 self.print_ident(*ident);

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -1225,7 +1225,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             }
 
             LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
-                binding_mode: BindingMode(ByRef::Yes(_), _),
+                binding_mode: BindingMode(ByRef::Yes(..), _),
                 ..
             })) => {
                 let pattern_span: Span = local_decl.source_info.span;

compiler/rustc_borrowck/src/lib.rs

@@ -2472,7 +2472,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
 
                         // Check the kind of deref to decide
                         match base_ty.kind() {
-                            ty::Ref(_, _, mutbl) => {
+                            _ if let &ty::Ref(_, _, mutbl) = base_ty.kind() => {
                                 match mutbl {
                                     // Shared borrowed data is never mutable
                                     hir::Mutability::Not => Err(place),
@@ -2513,6 +2513,16 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                             _ => bug!("Deref of unexpected type: {:?}", base_ty),
                         }
                     }
+                    // Check as the inner reference type if it is a field projection
+                    // from the `&pin` pattern
+                    ProjectionElem::Field(FieldIdx::ZERO, _)
+                        if let Some(adt) =
+                            place_base.ty(self.body(), self.infcx.tcx).ty.ty_adt_def()
+                            && adt.is_pin()
+                            && self.infcx.tcx.features().pin_ergonomics() =>
+                    {
+                        self.is_mutable(place_base, is_local_mutation_allowed)
+                    }
                     // All other projections are owned by their base path, so mutable if
                     // base path is mutable
                     ProjectionElem::Field(..)

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2360,7 +2360,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                     debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
                     match base_ty.kind() {
-                        ty::Ref(ref_region, _, mutbl) => {
+                        _ if let &ty::Ref(ref_region, _, mutbl) = base_ty.kind() => {
+                            // FIXME(pin_ergonomics): handle `&pin mut|const T`
                             constraints.outlives_constraints.push(OutlivesConstraint {
                                 sup: ref_region.as_var(),
                                 sub: borrow_region.as_var(),

compiler/rustc_codegen_cranelift/src/base.rs

@@ -729,7 +729,7 @@ fn codegen_stmt<'tcx>(
                     let to_ty = fx.monomorphize(to_ty);
 
                     fn is_wide_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
-                        ty.builtin_deref(true).is_some_and(|pointee_ty| {
+                        ty.builtin_deref(true, fx.tcx).is_some_and(|pointee_ty| {
                             fx.tcx
                                 .type_has_metadata(pointee_ty, ty::TypingEnv::fully_monomorphized())
                         })

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -583,7 +583,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (base, offset); intrinsic);
             let offset = offset.load_scalar(fx);
 
-            let pointee_ty = base.layout().ty.builtin_deref(true).unwrap();
+            let pointee_ty = base.layout().ty.builtin_deref(true, fx.tcx).unwrap();
             let pointee_size = fx.layout_of(pointee_ty).size.bytes();
             let ptr_diff = if pointee_size != 1 {
                 fx.bcx.ins().imul_imm(offset, pointee_size as i64)
@@ -609,7 +609,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let val = val.load_scalar(fx);
             let count = count.load_scalar(fx);
 
-            let pointee_ty = dst.layout().ty.builtin_deref(true).unwrap();
+            let pointee_ty = dst.layout().ty.builtin_deref(true, fx.tcx).unwrap();
             let pointee_size = fx.layout_of(pointee_ty).size.bytes();
             let count = if pointee_size != 1 {
                 fx.bcx.ins().imul_imm(count, pointee_size as i64)
@@ -717,7 +717,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
 
             // Cranelift treats loads as volatile by default
             // FIXME correctly handle unaligned_volatile_load
-            let inner_layout = fx.layout_of(ptr.layout().ty.builtin_deref(true).unwrap());
+            let inner_layout = fx.layout_of(ptr.layout().ty.builtin_deref(true, fx.tcx).unwrap());
             let val = CValue::by_ref(Pointer::new(ptr.load_scalar(fx)), inner_layout);
             ret.write_cvalue(fx, val);
         }

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -897,7 +897,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr, offset); intrinsic);
 
             let (lane_count, ptr_lane_ty) = ptr.layout().ty.simd_size_and_type(fx.tcx);
-            let pointee_ty = ptr_lane_ty.builtin_deref(true).unwrap();
+            let pointee_ty = ptr_lane_ty.builtin_deref(true, fx.tcx).unwrap();
             let pointee_size = fx.layout_of(pointee_ty).size.bytes();
             let (ret_lane_count, ret_lane_ty) = ret.layout().ty.simd_size_and_type(fx.tcx);
             let ret_lane_layout = fx.layout_of(ret_lane_ty);

compiler/rustc_codegen_cranelift/src/num.rs

@@ -398,7 +398,7 @@ pub(crate) fn codegen_ptr_binop<'tcx>(
     let is_thin_ptr = in_lhs
         .layout()
         .ty
-        .builtin_deref(true)
+        .builtin_deref(true, fx.tcx)
         .map(|ty| !fx.tcx.type_has_metadata(ty, ty::TypingEnv::fully_monomorphized()))
         .unwrap_or(true);
 
@@ -411,7 +411,7 @@ pub(crate) fn codegen_ptr_binop<'tcx>(
                 codegen_compare_bin_op(fx, bin_op, false, lhs, rhs)
             }
             BinOp::Offset => {
-                let pointee_ty = in_lhs.layout().ty.builtin_deref(true).unwrap();
+                let pointee_ty = in_lhs.layout().ty.builtin_deref(true, fx.tcx).unwrap();
                 let (base, offset) = (in_lhs, in_rhs.load_scalar(fx));
                 let pointee_size = fx.layout_of(pointee_ty).size.bytes();
                 let ptr_diff = fx.bcx.ins().imul_imm(offset, pointee_size as i64);

compiler/rustc_codegen_cranelift/src/unsize.rs

@@ -138,7 +138,7 @@ pub(crate) fn coerce_unsized_into<'tcx>(
     let dst_ty = dst.layout().ty;
     let mut coerce_ptr = || {
         let (base, info) =
-            if fx.layout_of(src.layout().ty.builtin_deref(true).unwrap()).is_unsized() {
+            if fx.layout_of(src.layout().ty.builtin_deref(true, fx.tcx).unwrap()).is_unsized() {
                 let (old_base, old_info) = src.load_scalar_pair(fx);
                 unsize_ptr(fx, old_base, src.layout(), dst.layout(), Some(old_info))
             } else {

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -831,7 +831,7 @@ impl<'tcx> CPlace<'tcx> {
     }
 
     pub(crate) fn place_deref(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> CPlace<'tcx> {
-        let inner_layout = fx.layout_of(self.layout().ty.builtin_deref(true).unwrap());
+        let inner_layout = fx.layout_of(self.layout().ty.builtin_deref(true, fx.tcx).unwrap());
         if fx.tcx.type_has_metadata(inner_layout.ty, ty::TypingEnv::fully_monomorphized()) {
             let (addr, extra) = self.to_cvalue(fx).load_scalar_pair(fx);
             CPlace::for_ptr_with_extra(Pointer::new(addr), extra, inner_layout)

compiler/rustc_codegen_cranelift/src/vtable.rs

@@ -59,7 +59,8 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
 
         if let ty::Ref(_, ty, _) = arg.layout().ty.kind() {
             if ty.is_dyn_star() {
-                let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap());
+                let inner_layout =
+                    fx.layout_of(arg.layout().ty.builtin_deref(true, fx.tcx).unwrap());
                 let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout);
                 let ptr = dyn_star.place_field(fx, FieldIdx::ZERO).to_ptr();
                 let vtable =

compiler/rustc_hir/src/hir.rs

@@ -12,7 +12,7 @@ use rustc_ast::{
 pub use rustc_ast::{
     AssignOp, AssignOpKind, AttrId, AttrStyle, BinOp, BinOpKind, BindingMode, BorrowKind,
     BoundConstness, BoundPolarity, ByRef, CaptureBy, DelimArgs, ImplPolarity, IsAuto,
-    MetaItemInner, MetaItemLit, Movability, Mutability, UnOp,
+    MetaItemInner, MetaItemLit, Movability, Mutability, Pinnedness, UnOp,
 };
 use rustc_attr_data_structures::AttributeKind;
 use rustc_data_structures::fingerprint::Fingerprint;

compiler/rustc_hir_analysis/src/check/region.rs

@@ -659,7 +659,7 @@ fn resolve_local<'tcx>(
         // & expression, and its lifetime would be extended to the end of the block (due
         // to a different rule, not the below code).
         match pat.kind {
-            PatKind::Binding(hir::BindingMode(hir::ByRef::Yes(_), _), ..) => true,
+            PatKind::Binding(hir::BindingMode(hir::ByRef::Yes(..), _), ..) => true,
 
             PatKind::Struct(_, field_pats, _) => field_pats.iter().any(|fp| is_binding_pat(fp.pat)),
 

compiler/rustc_hir_pretty/src/lib.rs

@@ -1882,10 +1882,15 @@ impl<'a> State<'a> {
                 if mutbl.is_mut() {
                     self.word_nbsp("mut");
                 }
-                if let ByRef::Yes(rmutbl) = by_ref {
+                if let ByRef::Yes(pinnedness, rmutbl) = by_ref {
                     self.word_nbsp("ref");
+                    if pinnedness.is_pinned() {
+                        self.word_nbsp("pin");
+                    }
                     if rmutbl.is_mut() {
                         self.word_nbsp("mut");
+                    } else if pinnedness.is_pinned() {
+                        self.word_nbsp("const");
                     }
                 }
                 self.print_ident(ident);

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -985,7 +985,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                     // of the pattern, as this just looks confusing, instead use the span
                     // of the discriminant.
                     match bm.0 {
-                        hir::ByRef::Yes(m) => {
+                        hir::ByRef::Yes(_, m) => {
                             let bk = ty::BorrowKind::from_mutbl(m);
                             self.delegate.borrow_mut().borrow(place, discr_place.hir_id, bk);
                         }
@@ -1258,25 +1258,34 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                     .get(pat.hir_id)
                     .expect("missing binding mode");
 
-                if matches!(bm.0, hir::ByRef::Yes(_)) {
-                    // a bind-by-ref means that the base_ty will be the type of the ident itself,
-                    // but what we want here is the type of the underlying value being borrowed.
-                    // So peel off one-level, turning the &T into T.
-                    match self
-                        .cx
-                        .try_structurally_resolve_type(pat.span, base_ty)
-                        .builtin_deref(false)
-                    {
-                        Some(ty) => Ok(ty),
-                        None => {
-                            debug!("By-ref binding of non-derefable type");
-                            Err(self
-                                .cx
-                                .report_bug(pat.span, "by-ref binding of non-derefable type"))
+                match bm.0 {
+                    hir::ByRef::Yes(pinnedness, _) => {
+                        let base_ty = if pinnedness.is_pinned() {
+                            base_ty.pinned_ty().ok_or_else(|| {
+                                debug!("By-pin-ref binding of non-`Pin` type");
+                                self.cx.report_bug(pat.span, "by-pin-ref binding of non-`Pin` type")
+                            })?
+                        } else {
+                            base_ty
+                        };
+                        // a bind-by-ref means that the base_ty will be the type of the ident itself,
+                        // but what we want here is the type of the underlying value being borrowed.
+                        // So peel off one-level, turning the &T into T.
+                        match self
+                            .cx
+                            .try_structurally_resolve_type(pat.span, base_ty)
+                            .builtin_deref(false)
+                        {
+                            Some(ty) => Ok(ty),
+                            None => {
+                                debug!("By-ref binding of non-derefable type");
+                                Err(self
+                                    .cx
+                                    .report_bug(pat.span, "by-ref binding of non-derefable type"))
+                            }
                         }
                     }
-                } else {
-                    Ok(base_ty)
+                    _ => Ok(base_ty),
                 }
             }
             _ => Ok(base_ty),
@@ -1704,6 +1713,16 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                     };
                     self.pat_deref_temp(pat.hir_id, pat, target_ty)?
                 }
+                adjustment::PatAdjust::PinDeref => {
+                    let target_ty = match adjusts.peek() {
+                        Some(&&next_adjust) => next_adjust.source,
+                        // At the end of the deref chain, we get `pat`'s scrutinee.
+                        None => self.pat_ty_unadjusted(pat)?,
+                    };
+                    let kind = ProjectionKind::Field(FieldIdx::ZERO, FIRST_VARIANT);
+                    place_with_id = self.cat_projection(pat.hir_id, place_with_id, target_ty, kind);
+                    self.cat_deref(pat.hir_id, place_with_id)?
+                }
             };
         }
         drop(typeck_results); // explicitly release borrow of typeck results, just in case.