From 3115d8413af8599972c43a301514a0ad0d601c43 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Mon, 27 Dec 2021 15:35:01 -0800
Subject: [PATCH] Document units for `std::column`

---
 library/core/src/macros/mod.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index b18508186a618..c648cdab13206 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -1062,6 +1062,18 @@ pub(crate) mod builtin {
     /// let current_col = column!();
     /// println!("defined on column: {}", current_col);
     /// ```
+    ///
+    /// `column!` counts Unicode code points, not bytes or graphemes. As a result, the first two
+    /// invocations return the same value, but the third does not.
+    ///
+    /// ```
+    /// let a = ("foobar", column!()).1;
+    /// let b = ("人之初性本善", column!()).1;
+    /// let c = ("f̅o̅o̅b̅a̅r̅", column!()).1; // Uses combining overline (U+0305)
+    ///
+    /// assert_eq!(a, b);
+    /// assert_ne!(b, c);
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_builtin_macro]
     #[macro_export]