Avoid including text direction codepoints in lint messages

Author: matthewjasper

Cargo.lock

@@ -2101,6 +2101,7 @@ dependencies = [
 name = "lint-docs"
 version = "0.1.0"
 dependencies = [
+ "rustc-literal-escaper",
  "serde_json",
  "tempfile",
  "walkdir",

compiler/rustc_lint_defs/src/builtin.rs

@@ -7,8 +7,6 @@
 //! When removing a lint, make sure to also add a call to `register_removed` in
 //! compiler/rustc_lint/src/lib.rs.
 
-#![allow(text_direction_codepoint_in_literal)]
-
 use rustc_span::edition::Edition;
 
 use crate::{FutureIncompatibilityReason, declare_lint, declare_lint_pass};
@@ -3795,7 +3793,7 @@ declare_lint! {
     /// ```rust,compile_fail
     /// #![deny(text_direction_codepoint_in_comment)]
     /// fn main() {
-    ///     println!("{:?}"); // '‮');
+    #[doc = "    println!(\"{:?}\"); // '\u{202E}');"]
     /// }
     /// ```
     ///
@@ -3830,12 +3828,12 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ````rust,compile_fail
     /// #![deny(text_direction_codepoint_in_literal)]
     /// fn main() {
-    ///     println!("{:?}", '‮');
+    #[doc = "    println!(\"{:?}\", '\u{202E}');"]
     /// }
-    /// ```
+    /// ````
     ///
     /// {{produces}}
     ///

src/tools/lint-docs/Cargo.toml

@@ -7,6 +7,7 @@ description = "A script to extract the lint documentation for the rustc book."
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rustc-literal-escaper = "0.0.2"
 serde_json = "1.0.57"
 tempfile = "3.1.0"
 walkdir = "2.3.1"

src/tools/lint-docs/src/lib.rs

@@ -4,6 +4,7 @@ use std::fs;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
+use rustc_literal_escaper::{Mode, unescape_unicode};
 use walkdir::WalkDir;
 
 mod groups;
@@ -214,6 +215,16 @@ impl<'a> LintExtractor<'a> {
                         let line = line.trim();
                         if let Some(text) = line.strip_prefix("/// ") {
                             doc_lines.push(text.to_string());
+                        } else if let Some(text) = line.strip_prefix("#[doc = \"") {
+                            let escaped = text.strip_suffix("\"]").unwrap();
+                            let mut buf = String::new();
+                            unescape_unicode(escaped, Mode::Str, &mut |_, c| match c {
+                                Ok(c) => buf.push(c),
+                                Err(err) => {
+                                    assert!(!err.is_fatal(), "failed to unescape string literal")
+                                }
+                            });
+                            doc_lines.push(buf);
                         } else if line == "///" {
                             doc_lines.push("".to_string());
                         } else if line.starts_with("// ") {