bugfix: correct escapes printer

src/res_printer.ml

@@ -552,7 +552,22 @@ let printConstant ?(templateLiteral = false) c =
  ]
  | Pconst_float (s, _) -> Doc.text s
  | Pconst_char c ->
- let str = Res_utf8.encodeCodePoint c in
+ let str =
+ if c <= 127 then
+ match Char.chr c with
+ | '\'' -> "\\'"
+ | '\\' -> "\\\\"
+ | '\n' -> "\\n"
+ | '\t' -> "\\t"
+ | '\r' -> "\\r"
+ | '\b' -> "\\b"
+ | ' ' .. '~' as c ->
+ let s = (Bytes.create [@doesNotRaise]) 1 in
+ Bytes.unsafe_set s 0 c;
+ Bytes.unsafe_to_string s
+ | _ -> Res_utf8.encodeCodePoint c
+ else Res_utf8.encodeCodePoint c
+ in
  Doc.text ("'" ^ str ^ "'")
 
 let printOptionalLabel attrs =