Auto merge of #96883 - jackh726:early-binder-2, r=oli-obk

Add EarlyBinder

Chalk has no concept of `Param` (https://github.com/rust-lang/chalk/blob/e0ade19d139bc784384acc6736cd960c91dd55a1/chalk-ir/src/lib.rs#L579) or `ReEarlyBound` (https://github.com/rust-lang/chalk/blob/e0ade19d139bc784384acc6736cd960c91dd55a1/chalk-ir/src/lib.rs#L1308). Everything  is just "bound" - the equivalent of rustc's late-bound. It's not completely clear yet whether to move everything to the same time of binder in rustc or add `Param` and `ReEarlyBound` in Chalk.

Either way, tracking when we have or haven't already substituted out these in rustc can be helpful.

As a first step, I'm just adding a `EarlyBinder` newtype that is required to call `subst`. I also add a couple "transparent" `bound_*` wrappers around a couple query that are often immediately substituted.

r? `@nikomatsakis`

6 files changed, 15 insertions, 13 deletions

diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index 6cb8c13946e..54c3cc46b26 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -18,7 +18,9 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
-use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{
+    self, ConstKind, EarlyBinder, Instance, ParamEnv, Ty, TyCtxt, TypeFoldable,
+};
 use rustc_span::{def_id::DefId, Span};
 use rustc_target::abi::{HasDataLayout, Size, TargetDataLayout};
 use rustc_target::spec::abi::Abi;
@@ -383,7 +385,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret = ecx
-            .layout_of(body.return_ty().subst(tcx, substs))
+            .layout_of(EarlyBinder(body.return_ty()).subst(tcx, substs))
             .ok()
             // Don't bother allocating memory for ZST types which have no values
             // or for large values.
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index a1ba1c0c0fc..6c0df98bc27 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -18,7 +18,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
 use rustc_middle::ty::{
-    self, ConstInt, ConstKind, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeFoldable,
+    self, ConstInt, ConstKind, EarlyBinder, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeFoldable,
 };
 use rustc_session::lint;
 use rustc_span::{def_id::DefId, Span};
@@ -378,7 +378,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret = ecx
-            .layout_of(body.return_ty().subst(tcx, substs))
+            .layout_of(EarlyBinder(body.return_ty()).subst(tcx, substs))
             .ok()
             // Don't bother allocating memory for ZST types which have no values
             // or for large values.
diff --git a/compiler/rustc_mir_transform/src/function_item_references.rs b/compiler/rustc_mir_transform/src/function_item_references.rs
index 2ed14b91778..1f9bd90d11f 100644
--- a/compiler/rustc_mir_transform/src/function_item_references.rs
+++ b/compiler/rustc_mir_transform/src/function_item_references.rs
@@ -6,7 +6,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::{
     self,
     subst::{GenericArgKind, Subst, SubstsRef},
-    PredicateKind, Ty, TyCtxt,
+    EarlyBinder, PredicateKind, Ty, TyCtxt,
 };
 use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
 use rustc_span::{symbol::sym, Span};
@@ -90,7 +90,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
                             // If the inner type matches the type bound by `Pointer`
                             if inner_ty == bound_ty {
                                 // Do a substitution using the parameters from the callsite
-                                let subst_ty = inner_ty.subst(self.tcx, substs_ref);
+                                let subst_ty = EarlyBinder(inner_ty).subst(self.tcx, substs_ref);
                                 if let Some((fn_id, fn_substs)) =
                                     FunctionItemRefChecker::is_fn_ref(subst_ty)
                                 {
diff --git a/compiler/rustc_mir_transform/src/generator.rs b/compiler/rustc_mir_transform/src/generator.rs
index d5d4bfa255b..b7dec57b757 100644
--- a/compiler/rustc_mir_transform/src/generator.rs
+++ b/compiler/rustc_mir_transform/src/generator.rs
@@ -247,7 +247,7 @@ impl<'tcx> TransformVisitor<'tcx> {
         assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 1);
         let ty = self
             .tcx
-            .type_of(self.state_adt_ref.variant(idx).fields[0].did)
+            .bound_type_of(self.state_adt_ref.variant(idx).fields[0].did)
             .subst(self.tcx, self.state_substs);
         expand_aggregate(
             Place::return_place(),
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 5e6dabeba6d..012ce730755 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -260,7 +260,7 @@ impl<'tcx> Inliner<'tcx> {
                     return None;
                 }
 
-                let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, substs);
+                let fn_sig = self.tcx.bound_fn_sig(def_id).subst(self.tcx, substs);
 
                 return Some(CallSite {
                     callee,
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index d10cac2ac76..016b3bc0980 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -4,7 +4,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, EarlyBinder, Ty, TyCtxt};
 use rustc_target::abi::VariantIdx;
 
 use rustc_index::vec::{Idx, IndexVec};
@@ -70,7 +70,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
             // of this function. Is this intentional?
             if let Some(ty::Generator(gen_def_id, substs, _)) = ty.map(Ty::kind) {
                 let body = tcx.optimized_mir(*gen_def_id).generator_drop().unwrap();
-                let body = body.clone().subst(tcx, substs);
+                let body = EarlyBinder(body.clone()).subst(tcx, substs);
                 debug!("make_shim({:?}) = {:?}", instance, body);
                 return body;
             }
@@ -151,7 +151,7 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
     } else {
         InternalSubsts::identity_for_item(tcx, def_id)
     };
-    let sig = tcx.fn_sig(def_id).subst(tcx, substs);
+    let sig = tcx.bound_fn_sig(def_id).subst(tcx, substs);
     let sig = tcx.erase_late_bound_regions(sig);
     let span = tcx.def_span(def_id);
 
@@ -343,7 +343,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         // otherwise going to be TySelf and we can't index
         // or access fields of a Place of type TySelf.
         let substs = tcx.mk_substs_trait(self_ty, &[]);
-        let sig = tcx.fn_sig(def_id).subst(tcx, substs);
+        let sig = tcx.bound_fn_sig(def_id).subst(tcx, substs);
         let sig = tcx.erase_late_bound_regions(sig);
         let span = tcx.def_span(def_id);
 
@@ -541,7 +541,7 @@ fn build_call_shim<'tcx>(
 
     assert_eq!(sig_substs.is_some(), !instance.has_polymorphic_mir_body());
     if let Some(sig_substs) = sig_substs {
-        sig = sig.subst(tcx, sig_substs);
+        sig = EarlyBinder(sig).subst(tcx, sig_substs);
     }
 
     if let CallKind::Indirect(fnty) = call_kind {