From 4d397bc1864e44f3cfdd788c3ef4c1b3e3ef06c0 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Mon, 4 Nov 2024 15:15:44 -0500
Subject: [PATCH] Add test of underscore variable in format string

---
 tests/ui/display-underscore.rs     | 7 +++++++
 tests/ui/display-underscore.stderr | 7 +++++++
 2 files changed, 14 insertions(+)
 create mode 100644 tests/ui/display-underscore.rs
 create mode 100644 tests/ui/display-underscore.stderr

diff --git a/tests/ui/display-underscore.rs b/tests/ui/display-underscore.rs
new file mode 100644
index 0000000..335614b
--- /dev/null
+++ b/tests/ui/display-underscore.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("{_}")]
+pub struct Error;
+
+fn main() {}
diff --git a/tests/ui/display-underscore.stderr b/tests/ui/display-underscore.stderr
new file mode 100644
index 0000000..36882b9
--- /dev/null
+++ b/tests/ui/display-underscore.stderr
@@ -0,0 +1,7 @@
+error: invalid format string: invalid argument name `_`
+ --> tests/ui/display-underscore.rs:4:11
+  |
+4 | #[error("{_}")]
+  |           ^ invalid argument name in format string
+  |
+  = note: argument name cannot be a single underscore