Do you mind sharing the patch you applied? If the issue is in go/types, I imagine that gopls itself does not have to be updated, but rather just rebuilt with the latest version of go from the dev.go2go branch.

It has to be updated sadly because brackets isn't the default in the go2go branch either (which I also hacked), the relevant patch for x/tools is:

diff --git a/go/loader/loader.go b/go/loader/loader.go
index bc12ca33..f3b45a01 100644
--- a/go/loader/loader.go
+++ b/go/loader/loader.go
@@ -1027,6 +1027,9 @@ func (imp *importer) addFiles(info *PackageInfo, files []*ast.File, cycleCheck b
 	} else {
 		// Ignore the returned (first) error since we
 		// already collect them all in the PackageInfo.
+		for _, f := range files {
+			f.UseBrackets = true
+		}
 		info.checker.Files(files)
 		info.Files = append(info.Files, files...)
 	}

Hm, I'm not sure that anything in gopls uses go/loader, but I can look into this tomorrow.

I also have a similar patch in go/src/go/types/check.go Checker.checkFiles, I pretty much ack'ed for checker.Files and manually changed it in all the places I saw, so ymmv.

Yeah, it will be the go/types version that made gopls work, but if that's an exported field we can set it in gopls itself.
Do you mind sharing a code snippet that reproduces the problem?

Based on https://groups.google.com/forum/?oldui=1#!topic/golang-nuts/iAD0NBz3DYw, it seems to me that there should be no reason to hardcode anything to true here.

Seems like after the new set of updates from 2-3 days ago I no longer have to patch the stdlib.