make both panic display formats collapse frames

Author: KodrAus

library/std/src/backtrace.rs

@@ -399,12 +399,11 @@ impl fmt::Display for Backtrace {
         let mut f = backtrace_rs::BacktraceFmt::new(fmt, style, &mut print_path);
         f.add_context()?;
         for frame in frames {
-            let mut f = f.frame();
             if frame.symbols.is_empty() {
-                f.print_raw(frame.frame.ip(), None, None, None)?;
+                f.frame().print_raw(frame.frame.ip(), None, None, None)?;
             } else {
                 for symbol in frame.symbols.iter() {
-                    f.print_raw_with_column(
+                    f.frame().print_raw_with_column(
                         frame.frame.ip(),
                         symbol.name.as_ref().map(|b| backtrace_rs::SymbolName::new(b)),
                         symbol.filename.as_ref().map(|b| match b {

library/std/src/sys_common/backtrace.rs

@@ -71,7 +71,6 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
 
         let mut hit = false;
         let mut stop = false;
-        let mut frame_fmt = bt_fmt.frame();
         backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
             hit = true;
             if print_fmt == PrintFmt::Short {
@@ -88,15 +87,15 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
             }
 
             if start {
-                res = frame_fmt.symbol(frame, symbol);
+                res = bt_fmt.frame().symbol(frame, symbol);
             }
         });
         if stop {
             return false;
         }
         if !hit {
             if start {
-                res = frame_fmt.print_raw(frame.ip(), None, None, None);
+                res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
             }
         }