debug: warn users when debugging optimized binaries

[hyangah]

From #1446 by @JadenSimon

Delve allows users to debug optimized binaries, however, when using the Delve client it will warn you that the function is optimized after hitting a breakpoint. This means the user is not confused when local variables are not what they expect (i.e. missing or invalid). The Go extension's DA makes no attempt at alerting the user that they might be debugging an optimized binary, causing a lot of confusion when debugging does not work as expected. This is especially true when remote debugging, as it may be up to an external process to do the compilation.

@polinasok @suzmue Optimized bit is a property of Function. Is there any good way to surface this in UI/DAP?

[suzmue]

We could surface this in the variables pane since this would be the feature that is most affected by the optimized function.

An option:

Before:

After:

We could also send a warning message to the Debug Console, but this may be less visible.

[polinasok]

A pop-up would be ideal, but I don't know of a way to trigger it other than an error response, which wouldn't apply here. I agree that logging to Debug Console might get lost (although we could make it more noticeable with stderr context color) and something more visible would be helpful. Labeling variable scopes is pretty clever.

[suzmue]

This has now been implemented in delve dap, by adding the annotation to the scope name:

@JadenSimon @polinasok @hyangah Is this sufficient? If you think this takes care of the problem we can close this issue.

[JadenSimon]

Yeah looks great!