Auto merge of rust-lang#97447 - nnethercote:improve-folding, r=jackh726

Folding revamp

r? `@ghost`

Author: bors

compiler/rustc_const_eval/src/interpret/util.rs

@@ -1,5 +1,5 @@
 use rustc_middle::mir::interpret::InterpResult;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitor};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor};
 use std::convert::TryInto;
 use std::ops::ControlFlow;
 
@@ -47,7 +47,7 @@ where
                         match (is_used, subst.needs_subst()) {
                             // Just in case there are closures or generators within this subst,
                             // recurse.
-                            (true, true) => return subst.super_visit_with(self),
+                            (true, true) => return subst.visit_with(self),
                             // Confirm that polymorphization replaced the parameter with
                             // `ty::Param`/`ty::ConstKind::Param`.
                             (false, true) if cfg!(debug_assertions) => match subst.unpack() {

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -11,7 +11,7 @@ use crate::infer::canonical::{
 };
 use crate::infer::InferCtxt;
 use rustc_middle::ty::flags::FlagComputation;
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
+use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::subst::GenericArg;
 use rustc_middle::ty::{self, BoundVar, InferConst, List, Ty, TyCtxt, TypeFlags};
 use std::sync::atomic::Ordering;

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -70,7 +70,7 @@ use rustc_middle::ty::{
     self,
     error::TypeError,
     subst::{GenericArgKind, Subst, SubstsRef},
-    Binder, EarlyBinder, List, Region, Ty, TyCtxt, TypeFoldable,
+    Binder, EarlyBinder, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
 };
 use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
 use rustc_target::spec::abi;

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -10,7 +10,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{self as hir, GenericBound, Item, ItemKind, Lifetime, LifetimeName, Node, TyKind};
 use rustc_middle::ty::{
-    self, AssocItemContainer, StaticLifetimeVisitor, Ty, TyCtxt, TypeFoldable, TypeVisitor,
+    self, AssocItemContainer, StaticLifetimeVisitor, Ty, TyCtxt, TypeSuperFoldable, TypeVisitor,
 };
 use rustc_span::symbol::Ident;
 use rustc_span::Span;

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -11,7 +11,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::Visitor;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::print::RegionHighlightMode;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitor};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperFoldable, TypeVisitor};
 use rustc_span::{Span, Symbol};
 
 use std::ops::ControlFlow;

compiler/rustc_infer/src/infer/freshen.rs

@@ -34,7 +34,7 @@ use super::InferCtxt;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::infer::unify_key::ToType;
 use rustc_middle::ty::fold::TypeFolder;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
 use std::collections::hash_map::Entry;
 
 pub struct TypeFreshener<'a, 'tcx> {
@@ -228,12 +228,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
                     .probe_value(v)
                     .val
                     .known();
-                return self.freshen_const(
-                    opt_ct,
-                    ty::InferConst::Var(v),
-                    ty::InferConst::Fresh,
-                    ct.ty(),
-                );
+                self.freshen_const(opt_ct, ty::InferConst::Var(v), ty::InferConst::Fresh, ct.ty())
             }
             ty::ConstKind::Infer(ty::InferConst::Fresh(i)) => {
                 if i >= self.const_freshen_count {
@@ -244,7 +239,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
                         self.const_freshen_count,
                     );
                 }
-                return ct;
+                ct
             }
 
             ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
@@ -254,9 +249,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             ty::ConstKind::Param(_)
             | ty::ConstKind::Value(_)
             | ty::ConstKind::Unevaluated(..)
-            | ty::ConstKind::Error(_) => {}
+            | ty::ConstKind::Error(_) => ct.super_fold_with(self),
         }
-
-        ct.super_fold_with(self)
     }
 }

compiler/rustc_infer/src/infer/fudge.rs

@@ -1,4 +1,4 @@
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
+use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid};
 
 use super::type_variable::TypeVariableOrigin;

compiler/rustc_infer/src/infer/mod.rs

@@ -23,7 +23,7 @@ use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKin
 use rustc_middle::mir::interpret::{ErrorHandled, EvalToConstValueResult};
 use rustc_middle::traits::select;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
+use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::relate::RelateResult;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
 pub use rustc_middle::ty::IntVarValue;

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -27,7 +27,7 @@ use crate::infer::{ConstVarValue, ConstVariableValue};
 use crate::infer::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::ty::error::TypeError;
-use rustc_middle::ty::fold::{TypeFoldable, TypeVisitor};
+use rustc_middle::ty::fold::{TypeFoldable, TypeSuperFoldable, TypeVisitor};
 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use rustc_middle::ty::{self, InferConst, Ty, TyCtxt};
 use rustc_span::Span;

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -9,7 +9,7 @@ use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::subst::{GenericArgKind, Subst};
 use rustc_middle::ty::{
-    self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitor,
+    self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor,
 };
 use rustc_span::Span;
 
@@ -470,7 +470,7 @@ where
         &mut self,
         t: &ty::Binder<'tcx, T>,
     ) -> ControlFlow<Self::BreakTy> {
-        t.as_ref().skip_binder().visit_with(self);
+        t.super_visit_with(self);
         ControlFlow::CONTINUE
     }