Tweak multispan rendering

Consider comments and bare delimiters the same as an "empty line" for purposes of hiding rendered code output of long multispans. This results in more aggressive shortening of rendered output without losing too much context, specially in `*.stderr` tests that have "hidden" comments.

1 files changed, 6 insertions, 2 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 1b6c6edcc61..9595790d574 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -3048,11 +3048,15 @@ impl FileWithAnnotatedLines {
                 // working correctly.
                 let middle = min(ann.line_start + 4, ann.line_end);
                 // We'll show up to 4 lines past the beginning of the multispan start.
-                // We will *not* include the tail of lines that are only whitespace.
+                // We will *not* include the tail of lines that are only whitespace, a comment or
+                // a bare delimiter.
                 let until = (ann.line_start..middle)
                     .rev()
                     .filter_map(|line| file.get_line(line - 1).map(|s| (line + 1, s)))
-                    .find(|(_, s)| !s.trim().is_empty())
+                    .find(|(_, s)| {
+                        let s = s.trim();
+                        !["", "{", "}", "(", ")", "[", "]"].contains(&s) && !s.starts_with("//")
+                    })
                     .map(|(line, _)| line)
                     .unwrap_or(ann.line_start);
                 for line in ann.line_start + 1..until {