Support hiding indented leading number

Author: dtolnay

src/normalize.rs

@@ -457,7 +457,10 @@ fn is_ascii_lowercase_hex(s: &str) -> bool {
 
 // "10 | T: Send,"  ->  "   | T: Send,"
 fn hide_leading_numbers(line: &mut String) {
-    let n = line.bytes().take_while(u8::is_ascii_digit).count();
+    let n = line
+        .bytes()
+        .take_while(|b: &u8| *b == b' ' || b.is_ascii_digit())
+        .count();
     for i in 0..n {
         line.replace_range(i..i + 1, " ");
     }