Rollup merge of #110297 - kylematsuda:earlybinder_tcx_subst, r=BoxyUwU

Make `(try_)subst_and_normalize_erasing_regions` take `EarlyBinder`

Changes `subst_and_normalize_erasing_regions` and `try_subst_and_normalize_erasing_regions` to take  `EarlyBinder<T>` instead of `T`.

(related to #105779)

This was suggested by `@BoxyUwU` in https://github.com/rust-lang/rust/pull/107753#discussion_r1105828139. After changing `type_of` to return `EarlyBinder`, there were several places where the binder was immediately skipped to call `tcx.subst_and_normalize_erasing_regions`, only for the binder to be reconstructed inside of that method.

r? `@BoxyUwU`

compiler/rustc_codegen_cranelift/src/common.rs

@@ -361,7 +361,7 @@ impl<'tcx> FunctionCx<'_, '_, 'tcx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.tcx,
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 

compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs

@@ -93,7 +93,7 @@ fn make_mir_scope<'ll, 'tcx>(
             let callee = cx.tcx.subst_and_normalize_erasing_regions(
                 instance.substs,
                 ty::ParamEnv::reveal_all(),
-                callee,
+                ty::EarlyBinder(callee),
             );
             let callee_fn_abi = cx.fn_abi_of_instance(callee, ty::List::empty());
             cx.dbg_scope_fn(callee, callee_fn_abi, None)

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -529,7 +529,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     let impl_self_ty = cx.tcx.subst_and_normalize_erasing_regions(
                         instance.substs,
                         ty::ParamEnv::reveal_all(),
-                        cx.tcx.type_of(impl_def_id).skip_binder(),
+                        cx.tcx.type_of(impl_def_id),
                     );
 
                     // Only "class" methods are generally understood by LLVM,

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -111,7 +111,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.cx.tcx(),
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 }

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -495,7 +495,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> Result<T, InterpError<'tcx>> {
         frame
             .instance
-            .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value)
+            .try_subst_mir_and_normalize_erasing_regions(
+                *self.tcx,
+                self.param_env,
+                ty::EarlyBinder(value),
+            )
             .map_err(|_| err_inval!(TooGeneric))
     }
 

compiler/rustc_middle/src/ty/instance.rs

@@ -115,7 +115,7 @@ impl<'tcx> Instance<'tcx> {
     /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
     pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
         let ty = tcx.type_of(self.def.def_id());
-        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty.skip_binder())
+        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
     }
 
     /// Finds a crate that contains a monomorphization of this instance that
@@ -578,14 +578,15 @@ impl<'tcx> Instance<'tcx> {
         self.def.has_polymorphic_mir_body().then_some(self.substs)
     }
 
-    pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
+    pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: EarlyBinder<&T>) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Copy,
     {
+        let v = v.map_bound(|v| *v);
         if let Some(substs) = self.substs_for_mir_body() {
-            EarlyBinder(*v).subst(tcx, substs)
+            v.subst(tcx, substs)
         } else {
-            *v
+            v.skip_binder()
         }
     }
 
@@ -594,7 +595,7 @@ impl<'tcx> Instance<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        v: T,
+        v: EarlyBinder<T>,
     ) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
@@ -602,7 +603,7 @@ impl<'tcx> Instance<'tcx> {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
         } else {
-            tcx.normalize_erasing_regions(param_env, v)
+            tcx.normalize_erasing_regions(param_env, v.skip_binder())
         }
     }
 
@@ -611,7 +612,7 @@ impl<'tcx> Instance<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        v: T,
+        v: EarlyBinder<T>,
     ) -> Result<T, NormalizationError<'tcx>>
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
@@ -619,7 +620,7 @@ impl<'tcx> Instance<'tcx> {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
         } else {
-            tcx.try_normalize_erasing_regions(param_env, v)
+            tcx.try_normalize_erasing_regions(param_env, v.skip_binder())
         }
     }
 

compiler/rustc_middle/src/ty/normalize_erasing_regions.rs

@@ -139,7 +139,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         param_substs: SubstsRef<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        value: T,
+        value: EarlyBinder<T>,
     ) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
@@ -151,7 +151,7 @@ impl<'tcx> TyCtxt<'tcx> {
              param_env={:?})",
             param_substs, value, param_env,
         );
-        let substituted = EarlyBinder(value).subst(self, param_substs);
+        let substituted = value.subst(self, param_substs);
         self.normalize_erasing_regions(param_env, substituted)
     }
 
@@ -163,7 +163,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         param_substs: SubstsRef<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        value: T,
+        value: EarlyBinder<T>,
     ) -> Result<T, NormalizationError<'tcx>>
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
@@ -175,7 +175,7 @@ impl<'tcx> TyCtxt<'tcx> {
              param_env={:?})",
             param_substs, value, param_env,
         );
-        let substituted = EarlyBinder(value).subst(self, param_substs);
+        let substituted = value.subst(self, param_substs);
         self.try_normalize_erasing_regions(param_env, substituted)
     }
 }

compiler/rustc_mir_transform/src/inline.rs

@@ -180,7 +180,7 @@ impl<'tcx> Inliner<'tcx> {
         let Ok(callee_body) = callsite.callee.try_subst_mir_and_normalize_erasing_regions(
             self.tcx,
             self.param_env,
-            callee_body.clone(),
+            ty::EarlyBinder(callee_body.clone()),
         ) else {
             return Err("failed to normalize callee body");
         };
@@ -444,7 +444,9 @@ impl<'tcx> Inliner<'tcx> {
                 work_list.push(target);
 
                 // If the place doesn't actually need dropping, treat it like a regular goto.
-                let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
+                let ty = callsite
+                    .callee
+                    .subst_mir(self.tcx, ty::EarlyBinder(&place.ty(callee_body, tcx).ty));
                 if ty.needs_drop(tcx, self.param_env) && let UnwindAction::Cleanup(unwind) = unwind {
                         work_list.push(unwind);
                     }
@@ -788,7 +790,9 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
         match terminator.kind {
             TerminatorKind::Drop { ref place, unwind, .. } => {
                 // If the place doesn't actually need dropping, treat it like a regular goto.
-                let ty = self.instance.subst_mir(tcx, &place.ty(self.callee_body, tcx).ty);
+                let ty = self
+                    .instance
+                    .subst_mir(tcx, ty::EarlyBinder(&place.ty(self.callee_body, tcx).ty));
                 if ty.needs_drop(tcx, self.param_env) {
                     self.cost += CALL_PENALTY;
                     if let UnwindAction::Cleanup(_) = unwind {
@@ -799,7 +803,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                 }
             }
             TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
-                let fn_ty = self.instance.subst_mir(tcx, &f.literal.ty());
+                let fn_ty = self.instance.subst_mir(tcx, ty::EarlyBinder(&f.literal.ty()));
                 self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind() && tcx.is_intrinsic(def_id) {
                     // Don't give intrinsics the extra penalty for calls
                     INSTR_COST

compiler/rustc_mir_transform/src/inline/cycle.rs

@@ -44,7 +44,11 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
     ) -> bool {
         trace!(%caller);
         for &(callee, substs) in tcx.mir_inliner_callees(caller.def) {
-            let Ok(substs) = caller.try_subst_mir_and_normalize_erasing_regions(tcx, param_env, substs) else {
+            let Ok(substs) = caller.try_subst_mir_and_normalize_erasing_regions(
+                tcx,
+                param_env,
+                ty::EarlyBinder(substs),
+            ) else {
                 trace!(?caller, ?param_env, ?substs, "cannot normalize, skipping");
                 continue;
             };

compiler/rustc_monomorphize/src/collector.rs

@@ -677,7 +677,7 @@ impl<'a, 'tcx> MirNeighborCollector<'a, 'tcx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.tcx,
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 }

compiler/rustc_monomorphize/src/partitioning/default.rs

@@ -310,7 +310,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
                     let impl_self_ty = tcx.subst_and_normalize_erasing_regions(
                         instance.substs,
                         ty::ParamEnv::reveal_all(),
-                        tcx.type_of(impl_def_id).skip_binder(),
+                        tcx.type_of(impl_def_id),
                     );
                     if let Some(def_id) = characteristic_def_id_of_type(impl_self_ty) {
                         return Some(def_id);

compiler/rustc_monomorphize/src/util.rs

@@ -29,12 +29,12 @@ pub(crate) fn dump_closure_profile<'tcx>(tcx: TyCtxt<'tcx>, closure_instance: In
         let before_feature_tys = tcx.subst_and_normalize_erasing_regions(
             closure_instance.substs,
             param_env,
-            before_feature_tys,
+            ty::EarlyBinder(before_feature_tys),
         );
         let after_feature_tys = tcx.subst_and_normalize_erasing_regions(
             closure_instance.substs,
             param_env,
-            after_feature_tys,
+            ty::EarlyBinder(after_feature_tys),
         );
 
         let new_size = tcx

compiler/rustc_ty_utils/src/instance.rs

@@ -27,8 +27,7 @@ fn resolve_instance<'tcx>(
         )
     } else {
         let ty = tcx.type_of(def);
-        let item_type =
-            tcx.subst_and_normalize_erasing_regions(substs, param_env, ty.skip_binder());
+        let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);
 
         let def = match *item_type.kind() {
             ty::FnDef(def_id, ..) if tcx.is_intrinsic(def_id) => {

src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -385,6 +385,9 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
             Node::Expr(parent_expr) => {
                 if let Some((callee_def_id, call_substs, recv, call_args)) = get_callee_substs_and_args(cx, parent_expr)
                 {
+                    // FIXME: the `subst_identity()` below seems incorrect, since we eventually
+                    // call `tcx.try_subst_and_normalize_erasing_regions` further down
+                    // (i.e., we are explicitly not in the identity context).
                     let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder();
                     if let Some(arg_index) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == expr.hir_id)
                         && let Some(param_ty) = fn_sig.inputs().get(arg_index)
@@ -435,7 +438,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                         let output_ty = fn_sig.output();
                         if output_ty.contains(*param_ty) {
                             if let Ok(new_ty)  = cx.tcx.try_subst_and_normalize_erasing_regions(
-                                new_subst, cx.param_env, output_ty) {
+                                new_subst, cx.param_env, EarlyBinder(output_ty)) {
                                 expr = parent_expr;
                                 ty = new_ty;
                                 continue;