Avoid ICE when suggestion span is at Eof

src/librustc_errors/lib.rs

@@ -229,7 +229,8 @@ impl CodeSuggestion {
                         }
                     }
                     if let Some(cur_line) = fm.get_line(cur_lo.line - 1) {
-                        buf.push_str(&cur_line[..cur_lo.col.to_usize()]);
+                        let end = std::cmp::min(cur_line.len(), cur_lo.col.to_usize());
+                        buf.push_str(&cur_line[..end]);
                     }
                 }
                 buf.push_str(&part.snippet);