modify insert_type_vars for lifetimes

crates/hir-ty/src/lib.rs

@@ -716,6 +716,55 @@ pub(crate) fn fold_tys_and_consts<T: HasInterner<Interner = Interner> + TypeFold
     t.fold_with(&mut TyFolder(f), binders)
 }
 
+pub(crate) fn fold_generic_args<T: HasInterner<Interner = Interner> + TypeFoldable<Interner>>(
+    t: T,
+    f: impl FnMut(GenericArgData, DebruijnIndex) -> GenericArgData,
+    binders: DebruijnIndex,
+) -> T {
+    use chalk_ir::fold::{TypeFolder, TypeSuperFoldable};
+    #[derive(chalk_derive::FallibleTypeFolder)]
+    #[has_interner(Interner)]
+    struct TyFolder<F: FnMut(GenericArgData, DebruijnIndex) -> GenericArgData>(F);
+    impl<F: FnMut(GenericArgData, DebruijnIndex) -> GenericArgData> TypeFolder<Interner>
+        for TyFolder<F>
+    {
+        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner> {
+            self
+        }
+
+        fn interner(&self) -> Interner {
+            Interner
+        }
+
+        fn fold_ty(&mut self, ty: Ty, outer_binder: DebruijnIndex) -> Ty {
+            let ty = ty.super_fold_with(self.as_dyn(), outer_binder);
+            self.0(GenericArgData::Ty(ty), outer_binder)
+                .intern(Interner)
+                .ty(Interner)
+                .unwrap()
+                .clone()
+        }
+
+        fn fold_const(&mut self, c: Const, outer_binder: DebruijnIndex) -> Const {
+            self.0(GenericArgData::Const(c), outer_binder)
+                .intern(Interner)
+                .constant(Interner)
+                .unwrap()
+                .clone()
+        }
+
+        fn fold_lifetime(&mut self, lt: Lifetime, outer_binder: DebruijnIndex) -> Lifetime {
+            let lt = lt.super_fold_with(self.as_dyn(), outer_binder);
+            self.0(GenericArgData::Lifetime(lt), outer_binder)
+                .intern(Interner)
+                .lifetime(Interner)
+                .unwrap()
+                .clone()
+        }
+    }
+    t.fold_with(&mut TyFolder(f), binders)
+}
+
 /// 'Canonicalizes' the `t` by replacing any errors with new variables. Also
 /// ensures there are no unbound variables or inference variables anywhere in
 /// the `t`.