Auto merge of #101857 - lcnr:make-dyn-again, r=jackh726

change `FnMutDelegate` to trait objects

cc #100016 as mentioned in the last t-compiler meeting

r? `@jackh726`

3 files changed, 20 insertions, 23 deletions

diff --git a/compiler/rustc_infer/src/infer/canonical/substitute.rs b/compiler/rustc_infer/src/infer/canonical/substitute.rs
index 34b6113427d..389afe22eb7 100644
--- a/compiler/rustc_infer/src/infer/canonical/substitute.rs
+++ b/compiler/rustc_infer/src/infer/canonical/substitute.rs
@@ -72,15 +72,16 @@ where
         value
     } else {
         let delegate = FnMutDelegate {
-            regions: |br: ty::BoundRegion| match var_values.var_values[br.var].unpack() {
+            regions: &mut |br: ty::BoundRegion| match var_values.var_values[br.var].unpack() {
                 GenericArgKind::Lifetime(l) => l,
                 r => bug!("{:?} is a region but value is {:?}", br, r),
             },
-            types: |bound_ty: ty::BoundTy| match var_values.var_values[bound_ty.var].unpack() {
+            types: &mut |bound_ty: ty::BoundTy| match var_values.var_values[bound_ty.var].unpack() {
                 GenericArgKind::Type(ty) => ty,
                 r => bug!("{:?} is a type but value is {:?}", bound_ty, r),
             },
-            consts: |bound_ct: ty::BoundVar, _| match var_values.var_values[bound_ct].unpack() {
+            consts: &mut |bound_ct: ty::BoundVar, _| match var_values.var_values[bound_ct].unpack()
+            {
                 GenericArgKind::Const(ct) => ct,
                 c => bug!("{:?} is a const but value is {:?}", bound_ct, c),
             },
diff --git a/compiler/rustc_infer/src/infer/higher_ranked/mod.rs b/compiler/rustc_infer/src/infer/higher_ranked/mod.rs
index 67426fcf0fe..0ce271c0e5d 100644
--- a/compiler/rustc_infer/src/infer/higher_ranked/mod.rs
+++ b/compiler/rustc_infer/src/infer/higher_ranked/mod.rs
@@ -81,19 +81,19 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let next_universe = self.create_next_universe();
 
         let delegate = FnMutDelegate {
-            regions: |br: ty::BoundRegion| {
+            regions: &mut |br: ty::BoundRegion| {
                 self.tcx.mk_region(ty::RePlaceholder(ty::PlaceholderRegion {
                     universe: next_universe,
                     name: br.kind,
                 }))
             },
-            types: |bound_ty: ty::BoundTy| {
+            types: &mut |bound_ty: ty::BoundTy| {
                 self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
                     universe: next_universe,
                     name: bound_ty.var,
                 }))
             },
-            consts: |bound_var: ty::BoundVar, ty| {
+            consts: &mut |bound_var: ty::BoundVar, ty| {
                 self.tcx.mk_const(ty::ConstS {
                     kind: ty::ConstKind::Placeholder(ty::PlaceholderConst {
                         universe: next_universe,
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index ed0eefd98ad..cac95e14a23 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -388,17 +388,13 @@ pub trait BoundVarReplacerDelegate<'tcx> {
     fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx>;
 }
 
-pub struct FnMutDelegate<R, T, C> {
-    pub regions: R,
-    pub types: T,
-    pub consts: C,
+pub struct FnMutDelegate<'a, 'tcx> {
+    pub regions: &'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a),
+    pub types: &'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a),
+    pub consts: &'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> ty::Const<'tcx> + 'a),
 }
-impl<'tcx, R, T, C> BoundVarReplacerDelegate<'tcx> for FnMutDelegate<R, T, C>
-where
-    R: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
-    T: FnMut(ty::BoundTy) -> Ty<'tcx>,
-    C: FnMut(ty::BoundVar, Ty<'tcx>) -> ty::Const<'tcx>,
-{
+
+impl<'a, 'tcx> BoundVarReplacerDelegate<'tcx> for FnMutDelegate<'a, 'tcx> {
     fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> {
         (self.regions)(br)
     }
@@ -522,7 +518,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn replace_late_bound_regions_uncached<T, F>(
         self,
         value: Binder<'tcx, T>,
-        replace_regions: F,
+        mut replace_regions: F,
     ) -> T
     where
         F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
@@ -533,9 +529,9 @@ impl<'tcx> TyCtxt<'tcx> {
             value
         } else {
             let delegate = FnMutDelegate {
-                regions: replace_regions,
-                types: |b| bug!("unexpected bound ty in binder: {b:?}"),
-                consts: |b, ty| bug!("unexpected bound ct in binder: {b:?} {ty}"),
+                regions: &mut replace_regions,
+                types: &mut |b| bug!("unexpected bound ty in binder: {b:?}"),
+                consts: &mut |b, ty| bug!("unexpected bound ct in binder: {b:?} {ty}"),
             };
             let mut replacer = BoundVarReplacer::new(self, delegate);
             value.fold_with(&mut replacer)
@@ -595,19 +591,19 @@ impl<'tcx> TyCtxt<'tcx> {
         self.replace_escaping_bound_vars_uncached(
             value,
             FnMutDelegate {
-                regions: |r: ty::BoundRegion| {
+                regions: &mut |r: ty::BoundRegion| {
                     self.mk_region(ty::ReLateBound(
                         ty::INNERMOST,
                         ty::BoundRegion { var: shift_bv(r.var), kind: r.kind },
                     ))
                 },
-                types: |t: ty::BoundTy| {
+                types: &mut |t: ty::BoundTy| {
                     self.mk_ty(ty::Bound(
                         ty::INNERMOST,
                         ty::BoundTy { var: shift_bv(t.var), kind: t.kind },
                     ))
                 },
-                consts: |c, ty: Ty<'tcx>| {
+                consts: &mut |c, ty: Ty<'tcx>| {
                     self.mk_const(ty::ConstS {
                         kind: ty::ConstKind::Bound(ty::INNERMOST, shift_bv(c)),
                         ty,