fix: escape when displaying string literals

crates/erg_common/str.rs

@@ -200,6 +200,7 @@ impl Str {
         Str::rc(&self.chars().rev().collect::<String>())
     }
 
+    /// Note that replacements may be chained because it attempt to rewrite in sequence
     pub fn multi_replace(&self, paths: &[(&str, &str)]) -> Self {
         let mut self_ = self.to_string();
         for (from, to) in paths {
@@ -232,6 +233,24 @@ impl Str {
     pub fn find_sub<'a>(&self, pats: &[&'a str]) -> Option<&'a str> {
         pats.iter().find(|&&pat| self.contains(pat)).copied()
     }
+
+    /// ```
+    /// # use erg_common::str::Str;
+    /// let s = Str::rc("\n");
+    /// assert_eq!(&s.escape()[..], "\\n");
+    /// let s = Str::rc("\\");
+    /// assert_eq!(&s.escape()[..], "\\\\");
+    /// ```
+    pub fn escape(&self) -> Str {
+        self.multi_replace(&[
+            ("\\", "\\\\"),
+            ("\0", "\\0"),
+            ("\r", "\\r"),
+            ("\n", "\\n"),
+            ("\"", "\\\""),
+            ("\'", "\\'"),
+        ])
+    }
 }
 
 #[cfg(test)]

crates/erg_compiler/ty/value.rs

@@ -487,7 +487,7 @@ impl fmt::Debug for ValueObj {
                 }
                 Ok(())
             }
-            Self::Str(s) => write!(f, "\"{s}\""),
+            Self::Str(s) => write!(f, "\"{}\"", s.escape()),
             Self::Bool(b) => {
                 if *b {
                     write!(f, "True")