Here's a trivial crash output:

panic: runtime error: index out of range

goroutine 1 [running]:
panic(0x10c0be0, 0x11468b0)
	/Users/rsc/go/src/runtime/panic.go:531 +0x1cf
main.do(0xc42013f800, 0x4b, 0x80)
	/Users/rsc/src/rsc.io/tmp/diffguess/main.go:76 +0xa66
main.main()
	/Users/rsc/src/rsc.io/tmp/diffguess/main.go:32 +0x203

The first line number is useless. I instinctively clicked on it only to find myself in package runtime instead of my own code.

The crash output is supposed to show only non-runtime code by default. The first frame should be the line that panicked: the panic frame itself should not be shown.

This is a regression introduced when we added panic frames to show executing defers. That's fine to keep, but we don't need and shouldn't show the panic frame when it is the first thing we're going to print in the stack trace.