Fix to add MapFunction type back

Closes GH-6.
Closes GH-7.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>
Reviewed-by: Remco Haszing <remcohaszing@gmail.com>
Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Co-authored-by: Titus Wormer <tituswormer@gmail.com>

index.js

@@ -2,14 +2,21 @@
  * @typedef {import('unist').Node} Node
  */
 
+/**
+ * @template {Node} [Tree=Node]
+ * @typedef {import('./complex-types.js').MapFunction<Tree>} MapFunction
+ *   Function called with a node, its index, and its parent to produce a new
+ *   node.
+ */
+
 /**
  * Create a new tree by mapping all nodes with the given function.
  *
  * @template {Node} Tree
  *   Type of input tree.
  * @param {Tree} tree
  *   Tree to map.
- * @param {import('./complex-types').MapFunction<Tree>} mapFunction
+ * @param {MapFunction<Tree>} mapFunction
  *   Function called with a node, its index, and its parent to produce a new
  *   node.
  * @returns {Tree}

readme.md

@@ -133,8 +133,7 @@ if the original node has children, those are mapped instead.
 ## Types
 
 This package is fully typed with [TypeScript][].
-It exports a type `MapFunction<Tree extends Node = Node>` from
-`unist-util-map/complex-types.d.ts` to properly type `MapFunction`s.
+It exports a type `MapFunction<Tree extends Node = Node>` to properly type `MapFunction`s.
 
 ## Compatibility
 

test.js

@@ -46,6 +46,15 @@ test('unist-util-map', function (t) {
     'should work when passing an empty object'
   )
 
+  /** @type {Root} */
+  const tree = u('root', [u('node', [u('leaf', '1')]), u('leaf', '2')])
+
+  t.deepEqual(
+    map(tree, asIs),
+    tree,
+    'should support an explicitly typed `MapFunction`'
+  )
+
   t.end()
 
   /**
@@ -69,4 +78,11 @@ test('unist-util-map', function (t) {
   function addValue() {
     return {value: 'test'}
   }
+
+  /**
+   * @type {import('./index.js').MapFunction<Root>}
+   */
+  function asIs(node) {
+    return node
+  }
 })