Call destructors when dyn* object goes out of scope

Author: eholk

compiler/rustc_codegen_ssa/src/meth.rs

@@ -86,15 +86,14 @@ fn expect_dyn_trait_in_self<'tcx>(ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'
 /// The `trait_ref` encodes the erased self type. Hence if we are
 /// making an object `Foo<dyn Trait>` from a value of type `Foo<T>`, then
 /// `trait_ref` would map `T: Trait`.
+#[instrument(level = "debug", skip(cx))]
 pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
     cx: &Cx,
     ty: Ty<'tcx>,
     trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
 ) -> Cx::Value {
     let tcx = cx.tcx();
 
-    debug!("get_vtable(ty={:?}, trait_ref={:?})", ty, trait_ref);
-
     // Check the cache.
     if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
         return val;

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -16,7 +16,7 @@ use rustc_index::vec::Idx;
 use rustc_middle::mir::{self, AssertKind, SwitchTargets};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
-use rustc_middle::ty::{self, Instance, Ty, TypeVisitable, TraitObjectRepresentation};
+use rustc_middle::ty::{self, Instance, TraitObjectRepresentation, Ty, TypeVisitable};
 use rustc_span::source_map::Span;
 use rustc_span::{sym, Symbol};
 use rustc_symbol_mangling::typeid::typeid_for_fnabi;
@@ -451,7 +451,27 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
                 //
                 // SO THEN WE CAN USE THE ABOVE CODE.
-                todo!()
+                let virtual_drop = Instance {
+                    def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
+                    substs: drop_fn.substs,
+                };
+                debug!("ty = {:?}", ty);
+                debug!("drop_fn = {:?}", drop_fn);
+                debug!("args = {:?}", args);
+                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
+                let data = args[0];
+                let data_ty = bx.cx().backend_type(place.layout);
+                let vtable_ptr =
+                    bx.gep(data_ty, data, &[bx.cx().const_i32(0), bx.cx().const_i32(1)]);
+                let vtable = bx.load(bx.type_i8p(), vtable_ptr, abi::Align::ONE);
+                // Truncate vtable off of args list
+                args = &args[..1];
+                debug!("args' = {:?}", args);
+                (
+                    meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
+                        .get_fn(&mut bx, vtable, ty, &fn_abi),
+                    fn_abi,
+                )
             }
             _ => (bx.get_fn_addr(drop_fn), bx.fn_abi_of_instance(drop_fn, ty::List::empty())),
         };

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -4,13 +4,15 @@ use super::{FunctionCx, LocalRef};
 
 use crate::base;
 use crate::common::{self, IntPredicate};
+use crate::meth::get_vtable;
 use crate::traits::*;
 use crate::MemFlags;
 
 use rustc_middle::mir;
 use rustc_middle::mir::Operand;
 use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
+use rustc_middle::ty::TraitObjectRepresentation;
 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
 use rustc_span::source_map::{Span, DUMMY_SP};
 
@@ -271,14 +273,19 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    #[allow(unreachable_code, unused)] // FIXME: remove this
                     mir::CastKind::DynStar => {
                         let data = match operand.val {
                             OperandValue::Ref(_, _, _) => todo!(),
-                            OperandValue::Immediate(_) => todo!(),
+                            OperandValue::Immediate(v) => v,
                             OperandValue::Pair(_, _) => todo!(),
                         };
-                        let vtable = todo!();
+                        // FIXME: find the real vtable!
+                        let trait_ref = if let ty::Dynamic(data, _, TraitObjectRepresentation::Sized) = cast.ty.kind() {
+                            data.principal()
+                        } else {
+                            bug!("Only valid to do a DynStar cast into a DynStar type")
+                        };
+                        let vtable = get_vtable(bx.cx(), source.ty(self.mir, bx.tcx()), trait_ref);
                         OperandValue::Pair(data, vtable)
                     }
                     mir::CastKind::Pointer(

compiler/rustc_middle/src/ty/layout.rs

@@ -2751,6 +2751,7 @@ impl<'tcx> ty::Instance<'tcx> {
     // for `Instance` (e.g. typeck would use `Ty::fn_sig` instead),
     // or should go through `FnAbi` instead, to avoid losing any
     // adjustments `fn_abi_of_instance` might be performing.
+    #[tracing::instrument(level = "debug", skip(tcx, param_env))]
     fn fn_sig_for_fn_abi(
         &self,
         tcx: TyCtxt<'tcx>,
@@ -2897,6 +2898,7 @@ impl<'tcx> ty::Instance<'tcx> {
 /// with `-Cpanic=abort` will look like they can't unwind when in fact they
 /// might (from a foreign exception or similar).
 #[inline]
+#[tracing::instrument(level = "debug", skip(tcx))]
 pub fn fn_can_unwind<'tcx>(tcx: TyCtxt<'tcx>, fn_def_id: Option<DefId>, abi: SpecAbi) -> bool {
     if let Some(did) = fn_def_id {
         // Special attribute for functions which can't unwind.
@@ -3113,6 +3115,7 @@ pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
     /// NB: that includes virtual calls, which are represented by "direct calls"
     /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
     #[inline]
+    #[tracing::instrument(level = "debug", skip(self))]
     fn fn_abi_of_instance(
         &self,
         instance: ty::Instance<'tcx>,
@@ -3259,6 +3262,10 @@ pub fn adjust_for_rust_scalar<'tcx>(
 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
     // FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
     // arguments of this method, into a separate `struct`.
+    #[tracing::instrument(
+        level = "debug",
+        skip(self, caller_location, fn_def_id, force_thin_self_ptr)
+    )]
     fn fn_abi_new_uncached(
         &self,
         sig: ty::PolyFnSig<'tcx>,
@@ -3268,8 +3275,6 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         // FIXME(eddyb) replace this with something typed, like an `enum`.
         force_thin_self_ptr: bool,
     ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
-        debug!("fn_abi_new_uncached({:?}, {:?})", sig, extra_args);
-
         let sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, sig);
 
         let conv = conv_from_spec_abi(self.tcx(), sig.abi);
@@ -3312,6 +3317,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall);
 
         let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
+            let span = tracing::debug_span!("arg_of");
+            let _entered = span.enter();
             let is_return = arg_idx.is_none();
 
             let layout = self.layout_of(ty)?;
@@ -3368,6 +3375,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         Ok(self.tcx.arena.alloc(fn_abi))
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     fn fn_abi_adjust_for_abi(
         &self,
         fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
@@ -3442,6 +3450,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
     }
 }
 
+#[tracing::instrument(level = "debug", skip(cx))]
 fn make_thin_self_ptr<'tcx>(
     cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
     layout: TyAndLayout<'tcx>,
@@ -3453,7 +3462,7 @@ fn make_thin_self_ptr<'tcx>(
         tcx.mk_mut_ptr(layout.ty)
     } else {
         match layout.abi {
-            Abi::ScalarPair(..) => (),
+            Abi::ScalarPair(..) | Abi::Scalar(..) => (),
             _ => bug!("receiver type has unsupported layout: {:?}", layout),
         }
 

compiler/rustc_middle/src/ty/normalize_erasing_regions.rs

@@ -36,6 +36,7 @@ impl<'tcx> TyCtxt<'tcx> {
     ///
     /// This should only be used outside of type inference. For example,
     /// it assumes that normalization will succeed.
+    #[tracing::instrument(level = "debug", skip(self, param_env))]
     pub fn normalize_erasing_regions<T>(self, param_env: ty::ParamEnv<'tcx>, value: T) -> T
     where
         T: TypeFoldable<'tcx>,
@@ -100,6 +101,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// N.B., currently, higher-ranked type bounds inhibit
     /// normalization. Therefore, each time we erase them in
     /// codegen, we need to normalize the contents.
+    #[tracing::instrument(level = "debug", skip(self, param_env))]
     pub fn normalize_erasing_late_bound_regions<T>(
         self,
         param_env: ty::ParamEnv<'tcx>,

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -216,10 +216,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 };
                 let from_ty = CastTy::from_ty(ty);
                 let cast_ty = CastTy::from_ty(expr.ty);
-                debug!(
-                    "ExprKind::Cast from_ty={from_ty:?}, cast_ty={:?}/{cast_ty:?}",
-                     expr.ty,
-                );
+                debug!("ExprKind::Cast from_ty={from_ty:?}, cast_ty={:?}/{cast_ty:?}", expr.ty,);
                 let cast_kind = match (from_ty, cast_ty) {
                     (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => {
                         CastKind::PointerExposeAddress

compiler/rustc_monomorphize/src/collector.rs

@@ -189,7 +189,8 @@ use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCast};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::{
-    self, GenericParamDefKind, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitable, VtblEntry,
+    self, GenericParamDefKind, Instance, TraitObjectRepresentation, Ty, TyCtxt, TypeFoldable,
+    TypeVisitable, VtblEntry,
 };
 use rustc_middle::{middle::codegen_fn_attrs::CodegenFnAttrFlags, mir::visit::TyContext};
 use rustc_session::config::EntryFnType;
@@ -689,7 +690,8 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                 mir::CastKind::Pointer(PointerCast::Unsize),
                 ref operand,
                 target_ty,
-            ) => {
+            )
+            | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
                 let target_ty = self.monomorphize(target_ty);
                 let source_ty = operand.ty(self.body, self.tcx);
                 let source_ty = self.monomorphize(source_ty);
@@ -698,7 +700,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                 // This could also be a different Unsize instruction, like
                 // from a fixed sized array to a slice. But we are only
                 // interested in things that produce a vtable.
-                if target_ty.is_trait() && !source_ty.is_trait() {
+                if (target_ty.is_trait() || target_ty.is_dyn_star()) && !source_ty.is_trait() {
                     create_mono_items_for_vtable_methods(
                         self.tcx,
                         target_ty,
@@ -1112,6 +1114,11 @@ fn find_vtable_types_for_unsizing<'tcx>(
             ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
         }
 
+        // T as dyn* Trait
+        (_, &ty::Dynamic(_, _, TraitObjectRepresentation::Sized)) => {
+            ptr_vtable(source_ty, target_ty)
+        }
+
         (&ty::Adt(source_adt_def, source_substs), &ty::Adt(target_adt_def, target_substs)) => {
             assert_eq!(source_adt_def, target_adt_def);
 

src/test/ui/dyn-star/make-dyn-star.rs

@@ -4,7 +4,7 @@
 use std::fmt::Debug;
 
 fn make_dyn_star(i: usize) {
-    let dyn_i: dyn* Debug = i as dyn* Debug;
+    let _dyn_i: dyn* Debug = i as dyn* Debug;
 }
 
 fn main() {