x/tools/gopls: incorrect edits from the unused variable quickfix

[findleyr]

Noticed this while preparing for the gopls@v0.9.2 release.

The new unused variable quickfix added in #48975 seems to compute over-large edits in some cases.

For example, given the following function:

The quick fix produces the following end-state:

I think this needs a bit more work before we enable this quick-fix by default.

CC @rentziass for awareness. This is not a big deal, but I probably won't promote this new feature in the v0.9.2 release notes. We'll promote it for v0.10.0 once we've worked on it a bit more.

[gopherbot]

Change https://go.dev/cl/640040 mentions this issue: gopls/internal/settings: document why unusedvariable is off

[gopherbot]

Change https://go.dev/cl/640579 mentions this issue: gopls/internal/analysis: unusedvariable