Simplify Literal::c_string implementation

Author: novafacing

library/proc_macro/src/lib.rs

@@ -1355,10 +1355,8 @@ impl Literal {
     /// C string literal.
     #[unstable(feature = "proc_macro_c_str_literals", issue = "119750")]
     pub fn c_string(string: &CStr) -> Literal {
-        let quoted = format!("{:?}", string);
-        assert!(quoted.starts_with('"') && quoted.ends_with('"'));
-        let symbol = &quoted[1..quoted.len() - 1];
-        Literal::new(bridge::LitKind::CStr, symbol, None)
+        let string = string.to_bytes().escape_ascii().to_string();
+        Literal::new(bridge::LitKind::CStr, &string, None)
     }
 
     /// Returns the span encompassing this literal.