Add typing to support readonly array properties of AST Node (prettier#15127)

* Add typing to support `readonly` array properties of AST Node

* add changelog

* fix changelog

* add test case

Author: auvred

changelog_unreleased/api/15127.md

@@ -0,0 +1,32 @@
+#### Add typing to support `readonly` array properties of AST Node (#15127 by @auvred)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+
+// Prettier stable
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+//                  ^ Argument of type '"readonlyArray"' is not assignable to parameter of type '"regularArray"'. ts(2345)
+
+// Prettier main
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+```

src/index.d.ts

@@ -33,7 +33,7 @@ type ArrayElement<T> = T extends Array<infer E> ? E : never;
 
 // A union of the properties of the given object that are arrays.
 type ArrayProperties<T> = {
-  [K in keyof T]: NonNullable<T[K]> extends any[] ? K : never;
+  [K in keyof T]: NonNullable<T[K]> extends readonly any[] ? K : never;
 }[keyof T];
 
 // A union of the properties of the given array T that can be used to index it.

tests/dts/unit/cases/print.ts

@@ -12,6 +12,7 @@ interface Nested2 {
   kind: "2";
   item3: Nested3;
   list3: Nested3[];
+  list5: readonly Nested3[];
 }
 interface Nested3 {
   kind: "3";
@@ -155,5 +156,7 @@ function print(
   // @ts-expect-error
   path.map(print, "item2", "item3");
 
+  path.map(print, "item2", "list5");
+
   return "";
 }