From 6a70b7e8d18e2b12a313d8e54e059b38598d6506 Mon Sep 17 00:00:00 2001
From: Max Heiber <mheiber@fb.com>
Date: Mon, 8 Aug 2022 11:44:09 -0700
Subject: [PATCH] test case for yielding a readonly key

Summary: Test case to ensure that we do readonly checking for the *key* in a yield expression

Reviewed By: jamesjwu

Differential Revision: D38491269

fbshipit-source-id: d06eb007fbc1326917226d2bf154c9fa7a05cec4
---
 .../typecheck/readonly/yield_expression_key.php    | 24 ++++++++++++++++++++++
 .../readonly/yield_expression_key.php.exp          |  2 ++
 2 files changed, 26 insertions(+)
 create mode 100644 hphp/hack/test/typecheck/readonly/yield_expression_key.php
 create mode 100644 hphp/hack/test/typecheck/readonly/yield_expression_key.php.exp

diff --git a/hphp/hack/test/typecheck/readonly/yield_expression_key.php b/hphp/hack/test/typecheck/readonly/yield_expression_key.php
new file mode 100644
index 00000000000..a75e2420f4e
--- /dev/null
+++ b/hphp/hack/test/typecheck/readonly/yield_expression_key.php
@@ -0,0 +1,24 @@
+<?hh
+
+function un_readonly<T>(readonly T $t): T {
+  foreach(generator($t) as $k => $_) {
+    return $k;
+  }
+  throw new Error("");
+}
+
+function generator<T>(readonly T $t): Generator<T, int, void> {
+  // should error here
+  yield ($t) => 1;
+}
+
+class Foo {
+  public function __construct(public int $prop) {}
+}
+
+<<__EntryPoint>>
+function main(): void {
+  $ro = readonly new Foo(2);
+  $mut = un_readonly($ro);
+  $mut->prop = 3; // should not be allowed: mutation of a readonly value
+}
diff --git a/hphp/hack/test/typecheck/readonly/yield_expression_key.php.exp b/hphp/hack/test/typecheck/readonly/yield_expression_key.php.exp
new file mode 100644
index 00000000000..135dd927d5b
--- /dev/null
+++ b/hphp/hack/test/typecheck/readonly/yield_expression_key.php.exp
@@ -0,0 +1,2 @@
+File "yield_expression_key.php", line 12, characters 10-11:
+This expression is readonly. We currently do not support yielding readonly values. (Parsing[1002])
-- 
2.11.4.GIT