Fix(mobx): Typescript pre-5.6 backwards compatibility

.changeset/packages/mobx/.changeset/odd-years-shop.md

@@ -0,0 +1,5 @@
+---
+"mobx": patch
+---
+
+Fix typescript backwards compatability for versions pre 5.6

packages/mobx/src/lib.2015.iterable.backfill-pre-5.6.d.ts

@@ -0,0 +1,29 @@
+// for backward compatability with typescript pre version 5.6
+// copied from https://github.com/microsoft/TypeScript/blob/main/src/lib/es2015.iterable.d.ts
+
+/**
+ * Defines the `TReturn` type used for built-in iterators produced by `Array`, `Map`, `Set`, and others.
+ * This is `undefined` when `strictBuiltInIteratorReturn` is `true`; otherwise, this is `any`.
+ */
+type BuiltinIteratorReturn = intrinsic;
+
+
+interface SetIterator<T> extends IteratorObject<T, BuiltinIteratorReturn, unknown> {
+    [Symbol.iterator](): SetIterator<T>;
+}
+
+/**
+ * Describes an {@link Iterator} produced by the runtime that inherits from the intrinsic `Iterator.prototype`.
+ */
+interface IteratorObject<T, TReturn = unknown, TNext = unknown> extends Iterator<T, TReturn, TNext> {
+    [Symbol.iterator](): IteratorObject<T, TReturn, TNext>;
+}
+
+interface MapIterator<T> extends IteratorObject<T, BuiltinIteratorReturn, unknown> {
+    [Symbol.iterator](): MapIterator<T>;
+}
+
+
+interface MapIterator<T> extends IteratorObject<T, BuiltinIteratorReturn, unknown> {
+    [Symbol.iterator](): MapIterator<T>;
+}