Document DirectiveFunctions

langs/en/guides/typescript.md

@@ -575,7 +575,7 @@ declare module "solid-js" {
 
 If you define custom directives for Solid's
 [`use:___` attributes](https://www.solidjs.com/docs/latest/api#use%3A___),
-you can type them in the `Directives` interface, like so:
+you can type them by extending the `DirectiveFunctions` interface, like so:
 
 ```tsx
 function model(element: HTMLInputElement, value: Accessor<Signal<string>>) {
@@ -586,8 +586,8 @@ function model(element: HTMLInputElement, value: Accessor<Signal<string>>) {
 
 declare module "solid-js" {
   namespace JSX {
-    interface Directives {  // use:model
-      model: Signal<string>;
+    interface DirectiveFunctions {  // use:model
+      model: typeof model;
     }
   }
 }
@@ -597,6 +597,19 @@ let [name, setName] = createSignal('');
 <input type="text" use:model={[name, setName]} />;
 ```
 
+If you just want to constrain the second argument to the directive function,
+you can extend the older `Directives` interface:
+
+```tsx
+declare module "solid-js" {
+  namespace JSX {
+    interface Directives {  // use:model
+      model: Signal<string>;
+    }
+  }
+}
+```
+
 If you're `import`ing a directive `d` from another module, and `d` is used only
 as a directive `use:d`, then TypeScript (or more precisely,
 [`babel-preset-typescript`](https://babeljs.io/docs/en/babel-preset-typescript))