From 587899e9ca5a836ffd71c6bd77885bb1f14c5b4a Mon Sep 17 00:00:00 2001
From: Paul Gey <narpfel@gmx.de>
Date: Mon, 16 Oct 2023 20:02:50 +0200
Subject: [PATCH] Preserve unicode escapes in format string literals when
 pretty-printing AST

---
 .../rustc_ast_pretty/src/pprust/state/expr.rs |  4 ++--
 tests/pretty/format-args-str-escape.pp        | 21 +++++++++++++++++++
 tests/pretty/format-args-str-escape.rs        | 10 +++++++++
 3 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 tests/pretty/format-args-str-escape.pp
 create mode 100644 tests/pretty/format-args-str-escape.rs

diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index 1142d492160d1..269cb8f238021 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -684,8 +684,8 @@ pub fn reconstruct_format_args_template_string(pieces: &[FormatArgsPiece]) -> St
     for piece in pieces {
         match piece {
             FormatArgsPiece::Literal(s) => {
-                for c in s.as_str().escape_debug() {
-                    template.push(c);
+                for c in s.as_str().chars() {
+                    template.extend(c.escape_debug());
                     if let '{' | '}' = c {
                         template.push(c);
                     }
diff --git a/tests/pretty/format-args-str-escape.pp b/tests/pretty/format-args-str-escape.pp
new file mode 100644
index 0000000000000..b84bc2303b733
--- /dev/null
+++ b/tests/pretty/format-args-str-escape.pp
@@ -0,0 +1,21 @@
+#![feature(prelude_import)]
+#![no_std]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+// pretty-compare-only
+// pretty-mode:expanded
+// pp-exact:format-args-str-escape.pp
+
+fn main() {
+    { ::std::io::_print(format_args!("\u{1b}[1mHello, world!\u{1b}[0m\n")); };
+    { ::std::io::_print(format_args!("\u{1b}[1mHello, world!\u{1b}[0m\n")); };
+    {
+        ::std::io::_print(format_args!("Not an escape sequence: \\u{{1B}}[1mbold\\x1B[0m\n"));
+    };
+    {
+        ::std::io::_print(format_args!("{0}\n",
+                "\x1B[1mHello, world!\x1B[0m"));
+    };
+}
diff --git a/tests/pretty/format-args-str-escape.rs b/tests/pretty/format-args-str-escape.rs
new file mode 100644
index 0000000000000..e596fcfd8bcba
--- /dev/null
+++ b/tests/pretty/format-args-str-escape.rs
@@ -0,0 +1,10 @@
+// pretty-compare-only
+// pretty-mode:expanded
+// pp-exact:format-args-str-escape.pp
+
+fn main() {
+    println!("\x1B[1mHello, world!\x1B[0m");
+    println!("\u{1B}[1mHello, world!\u{1B}[0m");
+    println!("Not an escape sequence: \\u{{1B}}[1mbold\\x1B[0m");
+    println!("{}", "\x1B[1mHello, world!\x1B[0m");
+}