From d9170dc6666211902c7fbfa4f229c43cc286890c Mon Sep 17 00:00:00 2001
From: Lzu Tao <taolzu@gmail.com>
Date: Thu, 11 Jul 2024 22:20:53 +0000
Subject: [PATCH] Add regression test for issue 127545

---
 .../transforming-option-ref-issue-127545.rs        |  6 ++++++
 .../transforming-option-ref-issue-127545.stderr    | 14 ++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 tests/ui/mismatched_types/transforming-option-ref-issue-127545.rs
 create mode 100644 tests/ui/mismatched_types/transforming-option-ref-issue-127545.stderr

diff --git a/tests/ui/mismatched_types/transforming-option-ref-issue-127545.rs b/tests/ui/mismatched_types/transforming-option-ref-issue-127545.rs
new file mode 100644
index 0000000000000..5ba58e7427581
--- /dev/null
+++ b/tests/ui/mismatched_types/transforming-option-ref-issue-127545.rs
@@ -0,0 +1,6 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/127545>.
+#![crate_type = "lib"]
+
+pub fn foo(arg: Option<&Vec<i32>>) -> Option<&[i32]> {
+    arg //~ ERROR 5:5: 5:8: mismatched types [E0308]
+}
diff --git a/tests/ui/mismatched_types/transforming-option-ref-issue-127545.stderr b/tests/ui/mismatched_types/transforming-option-ref-issue-127545.stderr
new file mode 100644
index 0000000000000..798a4da23b0d7
--- /dev/null
+++ b/tests/ui/mismatched_types/transforming-option-ref-issue-127545.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/transforming-option-ref-issue-127545.rs:5:5
+   |
+LL | pub fn foo(arg: Option<&Vec<i32>>) -> Option<&[i32]> {
+   |                                       -------------- expected `Option<&[i32]>` because of return type
+LL |     arg
+   |     ^^^ expected `Option<&[i32]>`, found `Option<&Vec<i32>>`
+   |
+   = note: expected enum `Option<&[i32]>`
+              found enum `Option<&Vec<i32>>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.