Partial future-proofing for Box<T, A>

src/liballoc/alloc.rs

@@ -16,7 +16,7 @@
             issue = "32838")]
 
 use core::intrinsics::{min_align_of_val, size_of_val};
-use core::ptr::NonNull;
+use core::ptr::{NonNull, Unique};
 use core::usize;
 
 #[doc(inline)]
@@ -170,9 +170,17 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     }
 }
 
-#[cfg_attr(not(test), lang = "box_free")]
+#[cfg(stage0)]
+#[lang = "box_free"]
+#[inline]
+unsafe fn old_box_free<T: ?Sized>(ptr: *mut T) {
+    box_free(Unique::new_unchecked(ptr))
+}
+
+#[cfg_attr(not(any(test, stage0)), lang = "box_free")]
 #[inline]
-pub(crate) unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
+pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
+    let ptr = ptr.as_ptr();
     let size = size_of_val(&*ptr);
     let align = min_align_of_val(&*ptr);
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.

src/liballoc/arc.rs

@@ -566,7 +566,8 @@ impl<T: ?Sized> Arc<T> {
 
     fn from_box(v: Box<T>) -> Arc<T> {
         unsafe {
-            let bptr = Box::into_raw(v);
+            let box_unique = Box::into_unique(v);
+            let bptr = box_unique.as_ptr();
 
             let value_size = size_of_val(&*bptr);
             let ptr = Self::allocate_for_ptr(bptr);
@@ -578,7 +579,7 @@ impl<T: ?Sized> Arc<T> {
                 value_size);
 
             // Free the allocation without dropping its contents
-            box_free(bptr);
+            box_free(box_unique);
 
             Arc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }

src/liballoc/rc.rs

@@ -681,7 +681,8 @@ impl<T: ?Sized> Rc<T> {
 
     fn from_box(v: Box<T>) -> Rc<T> {
         unsafe {
-            let bptr = Box::into_raw(v);
+            let box_unique = Box::into_unique(v);
+            let bptr = box_unique.as_ptr();
 
             let value_size = size_of_val(&*bptr);
             let ptr = Self::allocate_for_ptr(bptr);
@@ -693,7 +694,7 @@ impl<T: ?Sized> Rc<T> {
                 value_size);
 
             // Free the allocation without dropping its contents
-            box_free(bptr);
+            box_free(box_unique);
 
             Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }

src/librustc/ty/context.rs

@@ -34,7 +34,7 @@ use middle::resolve_lifetime::{self, ObjectLifetimeDefault};
 use middle::stability;
 use mir::{self, Mir, interpret};
 use mir::interpret::{Value, PrimVal};
-use ty::subst::{Kind, Substs};
+use ty::subst::{Kind, Substs, Subst};
 use ty::ReprOptions;
 use ty::Instance;
 use traits;
@@ -2319,7 +2319,15 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn mk_box(self, ty: Ty<'tcx>) -> Ty<'tcx> {
         let def_id = self.require_lang_item(lang_items::OwnedBoxLangItem);
         let adt_def = self.adt_def(def_id);
-        let substs = self.mk_substs(iter::once(Kind::from(ty)));
+        let generics = self.generics_of(def_id);
+        let mut substs = vec![Kind::from(ty)];
+        // Add defaults for other generic params if there are some.
+        for def in generics.types.iter().skip(1) {
+            assert!(def.has_default);
+            let ty = self.type_of(def.def_id).subst(self, &substs);
+            substs.push(ty.into());
+        }
+        let substs = self.mk_substs(substs.into_iter());
         self.mk_ty(TyAdt(adt_def, substs))
     }
 

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -918,11 +918,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     ));
                 }
 
-                if self.is_box_free(func) {
-                    self.check_box_free_inputs(mir, term, &sig, args, term_location);
-                } else {
-                    self.check_call_inputs(mir, term, &sig, args, term_location);
-                }
+                self.check_call_inputs(mir, term, &sig, args, term_location);
             }
             TerminatorKind::Assert {
                 ref cond, ref msg, ..
@@ -1026,70 +1022,6 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
         }
     }
 
-    fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
-        match *operand {
-            Operand::Constant(ref c) => match c.ty.sty {
-                ty::TyFnDef(ty_def_id, _) => {
-                    Some(ty_def_id) == self.tcx().lang_items().box_free_fn()
-                }
-                _ => false,
-            },
-            _ => false,
-        }
-    }
-
-    fn check_box_free_inputs(
-        &mut self,
-        mir: &Mir<'tcx>,
-        term: &Terminator<'tcx>,
-        sig: &ty::FnSig<'tcx>,
-        args: &[Operand<'tcx>],
-        term_location: Location,
-    ) {
-        debug!("check_box_free_inputs");
-
-        // box_free takes a Box as a pointer. Allow for that.
-
-        if sig.inputs().len() != 1 {
-            span_mirbug!(self, term, "box_free should take 1 argument");
-            return;
-        }
-
-        let pointee_ty = match sig.inputs()[0].sty {
-            ty::TyRawPtr(mt) => mt.ty,
-            _ => {
-                span_mirbug!(self, term, "box_free should take a raw ptr");
-                return;
-            }
-        };
-
-        if args.len() != 1 {
-            span_mirbug!(self, term, "box_free called with wrong # of args");
-            return;
-        }
-
-        let ty = args[0].ty(mir, self.tcx());
-        let arg_ty = match ty.sty {
-            ty::TyRawPtr(mt) => mt.ty,
-            ty::TyAdt(def, _) if def.is_box() => ty.boxed_ty(),
-            _ => {
-                span_mirbug!(self, term, "box_free called with bad arg ty");
-                return;
-            }
-        };
-
-        if let Err(terr) = self.sub_types(arg_ty, pointee_ty, term_location.at_self()) {
-            span_mirbug!(
-                self,
-                term,
-                "bad box_free arg ({:?} <- {:?}): {:?}",
-                pointee_ty,
-                arg_ty,
-                terr
-            );
-        }
-    }
-
     fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block_data: &BasicBlockData<'tcx>) {
         let is_cleanup = block_data.is_cleanup;
         self.last_span = block_data.terminator().source_info.span;

src/librustc_mir/transform/inline.rs

@@ -379,8 +379,6 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
             TerminatorKind::Call { args, destination: Some(destination), cleanup, .. } => {
                 debug!("Inlined {:?} into {:?}", callsite.callee, self.source);
 
-                let is_box_free = Some(callsite.callee) == self.tcx.lang_items().box_free_fn();
-
                 let mut local_map = IndexVec::with_capacity(callee_mir.local_decls.len());
                 let mut scope_map = IndexVec::with_capacity(callee_mir.visibility_scopes.len());
                 let mut promoted_map = IndexVec::with_capacity(callee_mir.promoted.len());
@@ -460,24 +458,8 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
 
                 let return_block = destination.1;
 
-                let args : Vec<_> = if is_box_free {
-                    assert!(args.len() == 1);
-                    // box_free takes a Box, but is defined with a *mut T, inlining
-                    // needs to generate the cast.
-                    // FIXME: we should probably just generate correct MIR in the first place...
-
-                    let arg = if let Operand::Move(ref place) = args[0] {
-                        place.clone()
-                    } else {
-                        bug!("Constant arg to \"box_free\"");
-                    };
-
-                    let ptr_ty = args[0].ty(caller_mir, self.tcx);
-                    vec![self.cast_box_free_arg(arg, ptr_ty, &callsite, caller_mir)]
-                } else {
-                    // Copy the arguments if needed.
-                    self.make_call_args(args, &callsite, caller_mir)
-                };
+                // Copy the arguments if needed.
+                let args: Vec<_> = self.make_call_args(args, &callsite, caller_mir);
 
                 let bb_len = caller_mir.basic_blocks().len();
                 let mut integrator = Integrator {
@@ -518,49 +500,6 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
         }
     }
 
-    fn cast_box_free_arg(&self, arg: Place<'tcx>, ptr_ty: Ty<'tcx>,
-                         callsite: &CallSite<'tcx>, caller_mir: &mut Mir<'tcx>) -> Local {
-        let arg = Rvalue::Ref(
-            self.tcx.types.re_erased,
-            BorrowKind::Mut { allow_two_phase_borrow: false },
-            arg.deref());
-
-        let ty = arg.ty(caller_mir, self.tcx);
-        let ref_tmp = LocalDecl::new_temp(ty, callsite.location.span);
-        let ref_tmp = caller_mir.local_decls.push(ref_tmp);
-        let ref_tmp = Place::Local(ref_tmp);
-
-        let ref_stmt = Statement {
-            source_info: callsite.location,
-            kind: StatementKind::Assign(ref_tmp.clone(), arg)
-        };
-
-        caller_mir[callsite.bb]
-            .statements.push(ref_stmt);
-
-        let pointee_ty = match ptr_ty.sty {
-            ty::TyRawPtr(tm) | ty::TyRef(_, tm) => tm.ty,
-            _ if ptr_ty.is_box() => ptr_ty.boxed_ty(),
-            _ => bug!("Invalid type `{:?}` for call to box_free", ptr_ty)
-        };
-        let ptr_ty = self.tcx.mk_mut_ptr(pointee_ty);
-
-        let raw_ptr = Rvalue::Cast(CastKind::Misc, Operand::Move(ref_tmp), ptr_ty);
-
-        let cast_tmp = LocalDecl::new_temp(ptr_ty, callsite.location.span);
-        let cast_tmp = caller_mir.local_decls.push(cast_tmp);
-
-        let cast_stmt = Statement {
-            source_info: callsite.location,
-            kind: StatementKind::Assign(Place::Local(cast_tmp), raw_ptr)
-        };
-
-        caller_mir[callsite.bb]
-            .statements.push(cast_stmt);
-
-        cast_tmp
-    }
-
     fn make_call_args(
         &self,
         args: Vec<Operand<'tcx>>,

src/librustc_mir/util/elaborate_drops.rs

@@ -337,18 +337,19 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         self.drop_ladder(fields, succ, unwind).0
     }
 
-    fn open_drop_for_box<'a>(&mut self, ty: Ty<'tcx>) -> BasicBlock
+    fn open_drop_for_box<'a>(&mut self, adt: &'tcx ty::AdtDef, substs: &'tcx Substs<'tcx>)
+                             -> BasicBlock
     {
-        debug!("open_drop_for_box({:?}, {:?})", self, ty);
+        debug!("open_drop_for_box({:?}, {:?}, {:?})", self, adt, substs);
 
         let interior = self.place.clone().deref();
         let interior_path = self.elaborator.deref_subpath(self.path);
 
         let succ = self.succ; // FIXME(#43234)
         let unwind = self.unwind;
-        let succ = self.box_free_block(ty, succ, unwind);
+        let succ = self.box_free_block(adt, substs, succ, unwind);
         let unwind_succ = self.unwind.map(|unwind| {
-            self.box_free_block(ty, unwind, Unwind::InCleanup)
+            self.box_free_block(adt, substs, unwind, Unwind::InCleanup)
         });
 
         self.drop_subpath(&interior, interior_path, succ, unwind_succ)
@@ -791,11 +792,12 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
             ty::TyTuple(tys) => {
                 self.open_drop_for_tuple(tys)
             }
-            ty::TyAdt(def, _) if def.is_box() => {
-                self.open_drop_for_box(ty.boxed_ty())
-            }
             ty::TyAdt(def, substs) => {
-                self.open_drop_for_adt(def, substs)
+                if def.is_box() {
+                    self.open_drop_for_box(def, substs)
+                } else {
+                    self.open_drop_for_adt(def, substs)
+                }
             }
             ty::TyDynamic(..) => {
                 let unwind = self.unwind; // FIXME(#43234)
@@ -858,28 +860,34 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
 
     fn box_free_block<'a>(
         &mut self,
-        ty: Ty<'tcx>,
+        adt: &'tcx ty::AdtDef,
+        substs: &'tcx Substs<'tcx>,
         target: BasicBlock,
         unwind: Unwind,
     ) -> BasicBlock {
-        let block = self.unelaborated_free_block(ty, target, unwind);
+        let block = self.unelaborated_free_block(adt, substs, target, unwind);
         self.drop_flag_test_block(block, target, unwind)
     }
 
     fn unelaborated_free_block<'a>(
         &mut self,
-        ty: Ty<'tcx>,
+        adt: &'tcx ty::AdtDef,
+        substs: &'tcx Substs<'tcx>,
         target: BasicBlock,
         unwind: Unwind
     ) -> BasicBlock {
         let tcx = self.tcx();
         let unit_temp = Place::Local(self.new_temp(tcx.mk_nil()));
         let free_func = tcx.require_lang_item(lang_items::BoxFreeFnLangItem);
-        let substs = tcx.mk_substs(iter::once(Kind::from(ty)));
+        let args = adt.variants[0].fields.iter().enumerate().map(|(i, f)| {
+            let field = Field::new(i);
+            let field_ty = f.ty(self.tcx(), substs);
+            Operand::Move(self.place.clone().field(field, field_ty))
+        }).collect();
 
         let call = TerminatorKind::Call {
             func: Operand::function_handle(tcx, free_func, substs, self.source_info.span),
-            args: vec![Operand::Move(self.place.clone())],
+            args: args,
             destination: Some((unit_temp, target)),
             cleanup: None
         }; // FIXME(#43234)