Reproduces on master.

Here's an interesting twist: https://play.golang.org/p/8G8BxckMZq

It seems to use the first method call as the position, so in the case above it uses the first GetB call, not the first GetA call. Probably the compiler recording the line number incorrectly, perhaps because it reuses something between these calls?

/cc @mdempsky

Change https://golang.org/cl/67470 mentions this issue: cmd/compile: Multiple invocations of an inlined function generate distinct panics

An incorrect traceback can be very confusing, so marking this as a 1.9.1 candidate.

Change https://golang.org/cl/67632 mentions this issue: cmd/compile: fix merge rules for panic calls

Reopening for 1.9.1 (or 1.9.2?)

This seems like a pretty subtle change. The win here is that some line numbers get fixed. Is that worth the risk? Should we just leave this for Go 1.10?

It's not the end of the world if doesn't get in 1.9. It's just backtrace line numbers, and needs a lot of things to happen to trigger it (inlining, bounds check fail or divide by zero, multiple identical call sites).

Two arguments in its favor:

• It is a regression from 1.8
• The fix is 2 lines

The fix is 2 lines but it affects the generated code, right? Because panics that were merged now are not. That could in turn affect other optimizations and might stir other issues around, right?

I think this is fairly important for 1.9, actually. The incorrect tracebacks have already led people to spend time poring over the wrong code. When the stack trace points you directly at a specific line, it's hard to understand that the problem is actually at a completely different, possibly quite distant, line in the same function.

@rsc Yes, it does affect the generated code. I'm not particularly worried about not merging two calls that we used to merge. That's the normal state, having unmergeable calls. That path is very well exercised.

CL 67632 OK for Go 1.9.2.

Change https://golang.org/cl/70980 mentions this issue: [release-branch.go1.9] cmd/compile: fix merge rules for panic calls

go1.9.2 has been packaged and includes:

• CL 67632

The release is posted at golang.org/dl.

— golang.org/x/build/cmd/releasebot, Oct 26 21:09:19 UTC