Auto merge of #112006 - kylematsuda:earlybinder-private, r=jackh726

Make `EarlyBinder`'s inner value private

Currently, `EarlyBinder(T)`'s inner value is public, which allows implicitly skipping the binder by indexing into the tuple struct (i.e., `x.0`). `@lcnr` suggested making `EarlyBinder`'s inner value private so users are required to explicitly call `skip_binder` (https://github.com/rust-lang/rust/issues/105779#issuecomment-1549933424) .

This PR makes the inner value private, adds `EarlyBinder::new` for constructing a new instance, and replaces uses of `x.0` with `x.skip_binder()` (or similar). It also adds some documentation to `EarlyBinder::skip_binder` explaining how to skip the binder of `&EarlyBinder<T>` to get `&T` now that the inner value is private (since previously we could just do `&x.0`).

r? `@lcnr`

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index ca1e209d504..e27d48fa8f6 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -192,7 +192,7 @@ impl<'tcx> Inliner<'tcx> {
         let Ok(callee_body) = callsite.callee.try_subst_mir_and_normalize_erasing_regions(
             self.tcx,
             self.param_env,
-            ty::EarlyBinder(callee_body.clone()),
+            ty::EarlyBinder::new(callee_body.clone()),
         ) else {
             return Err("failed to normalize callee body");
         };
@@ -455,7 +455,7 @@ impl<'tcx> Inliner<'tcx> {
                 // If the place doesn't actually need dropping, treat it like a regular goto.
                 let ty = callsite
                     .callee
-                    .subst_mir(self.tcx, ty::EarlyBinder(&place.ty(callee_body, tcx).ty));
+                    .subst_mir(self.tcx, ty::EarlyBinder::new(&place.ty(callee_body, tcx).ty));
                 if ty.needs_drop(tcx, self.param_env) && let UnwindAction::Cleanup(unwind) = unwind {
                     work_list.push(unwind);
                 }
@@ -790,7 +790,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                 // If the place doesn't actually need dropping, treat it like a regular goto.
                 let ty = self
                     .instance
-                    .subst_mir(tcx, ty::EarlyBinder(&place.ty(self.callee_body, tcx).ty));
+                    .subst_mir(tcx, ty::EarlyBinder::new(&place.ty(self.callee_body, tcx).ty));
                 if ty.needs_drop(tcx, self.param_env) {
                     self.cost += CALL_PENALTY;
                     if let UnwindAction::Cleanup(_) = unwind {
@@ -801,7 +801,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                 }
             }
             TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
-                let fn_ty = self.instance.subst_mir(tcx, ty::EarlyBinder(&f.literal.ty()));
+                let fn_ty = self.instance.subst_mir(tcx, ty::EarlyBinder::new(&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