Use escape_default() for strings in LitKind::token().

src/libsyntax/attr.rs

@@ -1228,10 +1228,7 @@ impl LitKind {
 
         match *self {
             LitKind::Str(string, ast::StrStyle::Cooked) => {
-                let mut escaped = String::new();
-                for ch in string.as_str().chars() {
-                    escaped.extend(ch.escape_unicode());
-                }
+                let escaped = string.as_str().escape_default();
                 Token::Literal(token::Lit::Str_(Symbol::intern(&escaped)), None)
             }
             LitKind::Str(string, ast::StrStyle::Raw(n)) => {

src/libsyntax/lib.rs

@@ -25,6 +25,7 @@
 #![feature(non_exhaustive)]
 #![feature(const_atomic_usize_new)]
 #![feature(rustc_attrs)]
+#![feature(str_escape)]
 
 #![recursion_limit="256"]
 

src/libsyntax/parse/mod.rs

@@ -298,14 +298,10 @@ pub fn char_lit(lit: &str, diag: Option<(Span, &Handler)>) -> (char, isize) {
     }
 }
 
-pub fn escape_default(s: &str) -> String {
-    s.chars().map(char::escape_default).flat_map(|x| x).collect()
-}
-
 /// Parse a string representing a string literal into its final form. Does
 /// unescaping.
 pub fn str_lit(lit: &str, diag: Option<(Span, &Handler)>) -> String {
-    debug!("parse_str_lit: given {}", escape_default(lit));
+    debug!("str_lit: given {}", lit.escape_default());
     let mut res = String::with_capacity(lit.len());
 
     let error = |i| format!("lexer should have rejected {} at {}", lit, i);
@@ -374,7 +370,7 @@ pub fn str_lit(lit: &str, diag: Option<(Span, &Handler)>) -> String {
 /// Parse a string representing a raw string literal into its final form. The
 /// only operation this does is convert embedded CRLF into a single LF.
 pub fn raw_str_lit(lit: &str) -> String {
-    debug!("raw_str_lit: given {}", escape_default(lit));
+    debug!("raw_str_lit: given {}", lit.escape_default());
     let mut res = String::with_capacity(lit.len());
 
     let mut chars = lit.chars().peekable();

src/libsyntax/print/pprust.rs

@@ -656,7 +656,7 @@ pub trait PrintState<'a> {
                     style: ast::StrStyle) -> io::Result<()> {
         let st = match style {
             ast::StrStyle::Cooked => {
-                (format!("\"{}\"", parse::escape_default(st)))
+                (format!("\"{}\"", st.escape_default()))
             }
             ast::StrStyle::Raw(n) => {
                 (format!("r{delim}\"{string}\"{delim}",