Fix rustdoc test

Author: estebank

compiler/rustc_errors/src/styled_buffer.rs

@@ -93,6 +93,9 @@ impl StyledBuffer {
         if start == end {
             return;
         }
+        if start > self.lines[line].len() || end > self.lines[line].len() {
+            return;
+        }
         let _ = self.lines[line].drain(start..(end - string.chars().count()));
         for (i, c) in string.chars().enumerate() {
             self.lines[line][start + i] = StyledChar::new(c, Style::LineNumber);

tests/rustdoc-ui/diagnostic-width.stderr

@@ -8,8 +8,8 @@ LL | ... a http://link.com
 note: the lint level is defined here
   --> $DIR/diagnostic-width.rs:2:9
    |
-LL | ...ny(rustdoc::bare_url...
-   |       ^^^^^^^^^^^^^^^^^^
+LL | ...ny(ru...are_urls)]
+   |       ^^...^^^^^^^^
 help: use an automatic link instead
    |
 LL | /// This is a long line that contains a <http://link.com>