Use ExistentialTraitRef throughout codegen

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -6,7 +6,7 @@ use cranelift_module::*;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{AllocId, GlobalAlloc, Scalar, read_target_uint};
-use rustc_middle::ty::{Binder, ExistentialTraitRef, ScalarInt};
+use rustc_middle::ty::{ExistentialTraitRef, ScalarInt};
 
 use crate::prelude::*;
 
@@ -167,7 +167,9 @@ pub(crate) fn codegen_const_value<'tcx>(
                             &mut fx.constants_cx,
                             fx.module,
                             ty,
-                            dyn_ty.principal(),
+                            dyn_ty.principal().map(|principal| {
+                                fx.tcx.instantiate_bound_regions_with_erased(principal)
+                            }),
                         );
                         let local_data_id =
                             fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
@@ -243,12 +245,9 @@ pub(crate) fn data_id_for_vtable<'tcx>(
     cx: &mut ConstantCx,
     module: &mut dyn Module,
     ty: Ty<'tcx>,
-    trait_ref: Option<Binder<'tcx, ExistentialTraitRef<'tcx>>>,
+    trait_ref: Option<ExistentialTraitRef<'tcx>>,
 ) -> DataId {
-    let alloc_id = tcx.vtable_allocation((
+    let alloc_id = tcx.vtable_allocation((ty, trait_ref));
-        ty,
-        trait_ref.map(|principal| tcx.instantiate_bound_regions_with_erased(principal)),
-    ));
     data_id_for_alloc_id(cx, module, alloc_id, Mutability::Not)
 }
 
@@ -463,9 +462,15 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
                 GlobalAlloc::Memory(target_alloc) => {
                     data_id_for_alloc_id(cx, module, alloc_id, target_alloc.inner().mutability)
                 }
-                GlobalAlloc::VTable(ty, dyn_ty) => {
+                GlobalAlloc::VTable(ty, dyn_ty) => data_id_for_vtable(
-                    data_id_for_vtable(tcx, cx, module, ty, dyn_ty.principal())
+                    tcx,
-                }
+                    cx,
+                    module,
+                    ty,
+                    dyn_ty
+                        .principal()
+                        .map(|principal| tcx.instantiate_bound_regions_with_erased(principal)),
+                ),
                 GlobalAlloc::Static(def_id) => {
                     if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
                     {

compiler/rustc_codegen_cranelift/src/unsize.rs

@@ -61,7 +61,12 @@ pub(crate) fn unsized_info<'tcx>(
                 old_info
             }
         }
-        (_, ty::Dynamic(data, ..)) => crate::vtable::get_vtable(fx, source, data.principal()),
+        (_, ty::Dynamic(data, ..)) => crate::vtable::get_vtable(
+            fx,
+            source,
+            data.principal()
+                .map(|principal| fx.tcx.instantiate_bound_regions_with_erased(principal)),
+        ),
         _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
     }
 }

compiler/rustc_codegen_cranelift/src/vtable.rs

@@ -90,7 +90,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
 pub(crate) fn get_vtable<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     ty: Ty<'tcx>,
-    trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
 ) -> Value {
     let data_id = data_id_for_vtable(fx.tcx, &mut fx.constants_cx, fx.module, ty, trait_ref);
     let local_data_id = fx.module.declare_data_in_func(data_id, fx.bcx.func);

compiler/rustc_codegen_gcc/src/context.rs

@@ -14,7 +14,7 @@ use rustc_middle::ty::layout::{
     FnAbiError, FnAbiOf, FnAbiOfHelpers, FnAbiRequest, HasTyCtxt, HasTypingEnv, LayoutError,
     LayoutOfHelpers,
 };
-use rustc_middle::ty::{self, Instance, PolyExistentialTraitRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, ExistentialTraitRef, Instance, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_span::source_map::respan;
 use rustc_span::{DUMMY_SP, Span};
@@ -90,7 +90,7 @@ pub struct CodegenCx<'gcc, 'tcx> {
     pub function_instances: RefCell<FxHashMap<Instance<'tcx>, Function<'gcc>>>,
     /// Cache generated vtables
     pub vtables:
-        RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), RValue<'gcc>>>,
+        RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), RValue<'gcc>>>,
 
     // TODO(antoyo): improve the SSA API to not require those.
     /// Mapping from function pointer type to indexes of on stack parameters.
@@ -401,7 +401,7 @@ impl<'gcc, 'tcx> BackendTypes for CodegenCx<'gcc, 'tcx> {
 impl<'gcc, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
     fn vtables(
         &self,
-    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<PolyExistentialTraitRef<'tcx>>), RValue<'gcc>>> {
+    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ExistentialTraitRef<'tcx>>), RValue<'gcc>>> {
         &self.vtables
     }
 

compiler/rustc_codegen_gcc/src/debuginfo.rs

@@ -7,7 +7,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::{self, Body, SourceScope};
-use rustc_middle::ty::{Instance, PolyExistentialTraitRef, Ty};
+use rustc_middle::ty::{ExistentialTraitRef, Instance, Ty};
 use rustc_session::config::DebugInfo;
 use rustc_span::{BytePos, Pos, SourceFile, SourceFileAndLine, Span, Symbol};
 use rustc_target::abi::Size;
@@ -214,7 +214,7 @@ impl<'gcc, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
     fn create_vtable_debuginfo(
         &self,
         _ty: Ty<'tcx>,
-        _trait_ref: Option<PolyExistentialTraitRef<'tcx>>,
+        _trait_ref: Option<ExistentialTraitRef<'tcx>>,
         _vtable: Self::Value,
     ) {
         // TODO(antoyo)

compiler/rustc_codegen_llvm/src/context.rs

@@ -77,8 +77,7 @@ pub(crate) struct CodegenCx<'ll, 'tcx> {
     /// Cache instances of monomorphic and polymorphic items
     pub instances: RefCell<FxHashMap<Instance<'tcx>, &'ll Value>>,
     /// Cache generated vtables
-    pub vtables:
+    pub vtables: RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), &'ll Value>>,
-        RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), &'ll Value>>,
     /// Cache of constant strings,
     pub const_str_cache: RefCell<FxHashMap<String, &'ll Value>>,
 
@@ -663,15 +662,14 @@ impl<'ll> SimpleCx<'ll> {
 impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     fn vtables(
         &self,
-    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), &'ll Value>>
+    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), &'ll Value>> {
-    {
         &self.vtables
     }
 
     fn apply_vcall_visibility_metadata(
         &self,
         ty: Ty<'tcx>,
-        poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+        poly_trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
         vtable: &'ll Value,
     ) {
         apply_vcall_visibility_metadata(self, ty, poly_trait_ref, vtable);

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -13,7 +13,7 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{HasTypingEnv, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{
-    self, AdtKind, CoroutineArgsExt, Instance, PolyExistentialTraitRef, Ty, TyCtxt, Visibility,
+    self, AdtKind, CoroutineArgsExt, ExistentialTraitRef, Instance, Ty, TyCtxt, Visibility,
 };
 use rustc_session::config::{self, DebugInfo, Lto};
 use rustc_span::{DUMMY_SP, FileName, FileNameDisplayPreference, SourceFile, Symbol, hygiene};
@@ -1400,13 +1400,13 @@ pub(crate) fn build_global_var_di_node<'ll>(
 fn build_vtable_type_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     ty: Ty<'tcx>,
-    poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    poly_trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
 ) -> &'ll DIType {
     let tcx = cx.tcx;
 
     let vtable_entries = if let Some(poly_trait_ref) = poly_trait_ref {
         let trait_ref = poly_trait_ref.with_self_ty(tcx, ty);
-        let trait_ref = tcx.erase_regions(tcx.instantiate_bound_regions_with_erased(trait_ref));
+        let trait_ref = tcx.erase_regions(trait_ref);
 
         tcx.vtable_entries(trait_ref)
     } else {
@@ -1491,7 +1491,7 @@ fn build_vtable_type_di_node<'ll, 'tcx>(
 pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     ty: Ty<'tcx>,
-    trait_ref: Option<PolyExistentialTraitRef<'tcx>>,
+    trait_ref: Option<ExistentialTraitRef<'tcx>>,
     vtable: &'ll Value,
 ) {
     // FIXME(flip1995): The virtual function elimination optimization only works with full LTO in
@@ -1510,7 +1510,7 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
 
     let trait_ref_self = trait_ref.with_self_ty(cx.tcx, ty);
     let trait_ref_self = cx.tcx.erase_regions(trait_ref_self);
-    let trait_def_id = trait_ref_self.def_id();
+    let trait_def_id = trait_ref_self.def_id;
     let trait_vis = cx.tcx.visibility(trait_def_id);
 
     let cgus = cx.sess().codegen_units().as_usize();
@@ -1569,7 +1569,7 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
 pub(crate) fn create_vtable_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     ty: Ty<'tcx>,
-    poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    poly_trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
     vtable: &'ll Value,
 ) {
     if cx.dbg_cx.is_none() {

compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs

@@ -6,7 +6,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::HashStable;
 use rustc_middle::bug;
-use rustc_middle::ty::{self, PolyExistentialTraitRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, ExistentialTraitRef, Ty, TyCtxt};
 
 use super::{DefinitionLocation, SmallVec, UNKNOWN_LINE_NUMBER, unknown_file_metadata};
 use crate::common::{AsCCharPtr, CodegenCx};
@@ -44,7 +44,7 @@ pub(super) enum UniqueTypeId<'tcx> {
     /// The ID for the additional wrapper struct type describing an enum variant in CPP-like mode.
     VariantStructTypeCppLikeWrapper(Ty<'tcx>, VariantIdx, private::HiddenZst),
     /// The ID of the artificial type we create for VTables.
-    VTableTy(Ty<'tcx>, Option<PolyExistentialTraitRef<'tcx>>, private::HiddenZst),
+    VTableTy(Ty<'tcx>, Option<ExistentialTraitRef<'tcx>>, private::HiddenZst),
 }
 
 impl<'tcx> UniqueTypeId<'tcx> {
@@ -88,7 +88,7 @@ impl<'tcx> UniqueTypeId<'tcx> {
     pub(crate) fn for_vtable_ty(
         tcx: TyCtxt<'tcx>,
         self_type: Ty<'tcx>,
-        implemented_trait: Option<PolyExistentialTraitRef<'tcx>>,
+        implemented_trait: Option<ExistentialTraitRef<'tcx>>,
     ) -> Self {
         assert_eq!(
             self_type,

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -585,7 +585,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     fn create_vtable_debuginfo(
         &self,
         ty: Ty<'tcx>,
-        trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+        trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
         vtable: Self::Value,
     ) {
         metadata::create_vtable_di_node(self, ty, trait_ref, vtable)

compiler/rustc_codegen_ssa/src/base.rs

@@ -25,7 +25,6 @@ use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType};
 use rustc_span::{DUMMY_SP, Symbol, sym};
-use rustc_trait_selection::infer::at::ToTrace;
 use rustc_trait_selection::infer::{BoundRegionConversionTime, TyCtxtInferExt};
 use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
 use tracing::{debug, info};
@@ -129,14 +128,9 @@ pub fn validate_trivial_unsize<'tcx>(
                     BoundRegionConversionTime::HigherRankedType,
                     hr_source_principal,
                 );
-                let Ok(()) = ocx.eq_trace(
+                let Ok(()) = ocx.eq(
                     &ObligationCause::dummy(),
                     param_env,
-                    ToTrace::to_trace(
-                        &ObligationCause::dummy(),
-                        hr_target_principal,
-                        hr_source_principal,
-                    ),
                     target_principal,
                     source_principal,
                 ) else {
@@ -211,7 +205,12 @@ fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 old_info
             }
         }
-        (_, ty::Dynamic(data, _, _)) => meth::get_vtable(cx, source, data.principal()),
+        (_, ty::Dynamic(data, _, _)) => meth::get_vtable(
+            cx,
+            source,
+            data.principal()
+                .map(|principal| bx.tcx().instantiate_bound_regions_with_erased(principal)),
+        ),
         _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
     }
 }

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -507,7 +507,7 @@ pub enum VTableNameKind {
 pub fn compute_debuginfo_vtable_name<'tcx>(
     tcx: TyCtxt<'tcx>,
     t: Ty<'tcx>,
-    trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
     kind: VTableNameKind,
 ) -> String {
     let cpp_like_debuginfo = cpp_like_debuginfo(tcx);
@@ -530,8 +530,8 @@ pub fn compute_debuginfo_vtable_name<'tcx>(
     }
 
     if let Some(trait_ref) = trait_ref {
-        let trait_ref = tcx
+        let trait_ref =
-            .normalize_erasing_late_bound_regions(ty::TypingEnv::fully_monomorphized(), trait_ref);
+            tcx.normalize_erasing_regions(ty::TypingEnv::fully_monomorphized(), trait_ref);
         push_item_name(tcx, trait_ref.def_id, true, &mut vtable_name);
         visited.clear();
         push_generic_params_internal(tcx, trait_ref.args, &mut vtable_name, &mut visited);

compiler/rustc_codegen_ssa/src/meth.rs

@@ -1,5 +1,5 @@
 use rustc_middle::bug;
-use rustc_middle::ty::{self, GenericArgKind, Ty};
+use rustc_middle::ty::{self, GenericArgKind, Ty, TyCtxt};
 use rustc_session::config::Lto;
 use rustc_symbol_mangling::typeid_for_trait_ref;
 use rustc_target::callconv::FnAbi;
@@ -72,12 +72,17 @@ impl<'a, 'tcx> VirtualIndex {
 
 /// This takes a valid `self` receiver type and extracts the principal trait
 /// ref of the type. Return `None` if there is no principal trait.
-fn dyn_trait_in_self(ty: Ty<'_>) -> Option<ty::PolyExistentialTraitRef<'_>> {
+fn dyn_trait_in_self<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    ty: Ty<'tcx>,
+) -> Option<ty::ExistentialTraitRef<'tcx>> {
     for arg in ty.peel_refs().walk() {
         if let GenericArgKind::Type(ty) = arg.unpack()
             && let ty::Dynamic(data, _, _) = ty.kind()
         {
-            return data.principal();
+            return data
+                .principal()
+                .map(|principal| tcx.instantiate_bound_regions_with_erased(principal));
         }
     }
 
@@ -96,28 +101,24 @@ fn dyn_trait_in_self(ty: Ty<'_>) -> Option<ty::PolyExistentialTraitRef<'_>> {
 pub(crate) fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
     cx: &Cx,
     ty: Ty<'tcx>,
-    poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
 ) -> Cx::Value {
     let tcx = cx.tcx();
 
     // Check the cache.
-    if let Some(&val) = cx.vtables().borrow().get(&(ty, poly_trait_ref)) {
+    if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
         return val;
     }
 
-    // FIXME(trait_upcasting): Take a non-higher-ranked vtable as arg.
-    let trait_ref =
-        poly_trait_ref.map(|trait_ref| tcx.instantiate_bound_regions_with_erased(trait_ref));
-
     let vtable_alloc_id = tcx.vtable_allocation((ty, trait_ref));
     let vtable_allocation = tcx.global_alloc(vtable_alloc_id).unwrap_memory();
     let vtable_const = cx.const_data_from_alloc(vtable_allocation);
     let align = cx.data_layout().pointer_align.abi;
     let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
 
-    cx.apply_vcall_visibility_metadata(ty, poly_trait_ref, vtable);
+    cx.apply_vcall_visibility_metadata(ty, trait_ref, vtable);
-    cx.create_vtable_debuginfo(ty, poly_trait_ref, vtable);
+    cx.create_vtable_debuginfo(ty, trait_ref, vtable);
-    cx.vtables().borrow_mut().insert((ty, poly_trait_ref), vtable);
+    cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
     vtable
 }
 
@@ -135,7 +136,7 @@ pub(crate) fn load_vtable<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     if bx.cx().sess().opts.unstable_opts.virtual_function_elimination
         && bx.cx().sess().lto() == Lto::Fat
     {
-        if let Some(trait_ref) = dyn_trait_in_self(ty) {
+        if let Some(trait_ref) = dyn_trait_in_self(bx.tcx(), ty) {
             let typeid = bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), trait_ref)).unwrap();
             let func = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
             return func;

compiler/rustc_codegen_ssa/src/traits/debuginfo.rs

@@ -2,7 +2,7 @@ use std::ops::Range;
 
 use rustc_abi::Size;
 use rustc_middle::mir;
-use rustc_middle::ty::{Instance, PolyExistentialTraitRef, Ty};
+use rustc_middle::ty::{ExistentialTraitRef, Instance, Ty};
 use rustc_span::{SourceFile, Span, Symbol};
 use rustc_target::callconv::FnAbi;
 
@@ -13,7 +13,7 @@ pub trait DebugInfoCodegenMethods<'tcx>: BackendTypes {
     fn create_vtable_debuginfo(
         &self,
         ty: Ty<'tcx>,
-        trait_ref: Option<PolyExistentialTraitRef<'tcx>>,
+        trait_ref: Option<ExistentialTraitRef<'tcx>>,
         vtable: Self::Value,
     );
 

compiler/rustc_codegen_ssa/src/traits/misc.rs

@@ -10,11 +10,11 @@ use super::BackendTypes;
 pub trait MiscCodegenMethods<'tcx>: BackendTypes {
     fn vtables(
         &self,
-    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), Self::Value>>;
+    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), Self::Value>>;
     fn apply_vcall_visibility_metadata(
         &self,
         _ty: Ty<'tcx>,
-        _poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+        _poly_trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
         _vtable: Self::Value,
     ) {
     }

compiler/rustc_symbol_mangling/src/lib.rs

@@ -151,7 +151,7 @@ fn symbol_name_provider<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> ty
 
 pub fn typeid_for_trait_ref<'tcx>(
     tcx: TyCtxt<'tcx>,
-    trait_ref: ty::PolyExistentialTraitRef<'tcx>,
+    trait_ref: ty::ExistentialTraitRef<'tcx>,
 ) -> String {
     v0::mangle_typeid_for_trait_ref(tcx, trait_ref)
 }

compiler/rustc_symbol_mangling/src/v0.rs

@@ -72,7 +72,7 @@ pub(super) fn mangle<'tcx>(
 
 pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
     tcx: TyCtxt<'tcx>,
-    trait_ref: ty::PolyExistentialTraitRef<'tcx>,
+    trait_ref: ty::ExistentialTraitRef<'tcx>,
 ) -> String {
     // FIXME(flip1995): See comment in `mangle_typeid_for_fnabi`.
     let mut cx = SymbolMangler {
@@ -84,7 +84,7 @@ pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
         binders: vec![],
         out: String::new(),
     };
-    cx.print_def_path(trait_ref.def_id(), &[]).unwrap();
+    cx.print_def_path(trait_ref.def_id, &[]).unwrap();
     std::mem::take(&mut cx.out)
 }