x/tools/go/analysis/cmd/vet: also whitelist unicode.Range32 to avoid "unkeyed fields in composite literal" error

[adiabatic]

What version of Go are you using (go version)?

$ go version
go version go1.12.5 darwin/amd64

Does this issue reproduce with the latest release?

Yes. 1.12.5 is the latest release available for macOS on golang.org/dl/.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/comatoast/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/comatoast/Projects/Go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/comatoast/Projects/quote-educator/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/wy/3sprnnbj2yx9h60jbs4qjvpr0000gn/T/go-build895608949=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I used struct literals without keys. go vet doesn't complain when it sees unicode.Range16{0xfdd0, 0xfdef, 1}, but complains when it sees unicode.Range32{0x1fffe, 0x1ffff, 1}.

Minimized test case: https://play.golang.org/p/atnHOc10YRs

Semi-minimized real-world example: https://play.golang.org/p/VzaW9okIUic

What did you expect to see?

No go vet errors. Or, now that I've researched a bit into how go vet should work, errors for using unicode.Range16 like this, too.

What did you see instead?

go vet errors on lines like unicode.Range32{0x1fffe, 0x1ffff, 1}. After seeing the discussion on #6820 I'm not sure why unicode.Range16 is fine but unicode.Range32 is warning-worthy.

[letientai299]

I've submitted a CL for this: https://go-review.googlesource.com/c/tools/+/180922

[gopherbot]

Change https://golang.org/cl/180922 mentions this issue: vet: whitelist unicode.Range32

[odeke-em]

Thank you for this report @adiabatic and for working on the fix @letientai299!

Since this cmd/vet is now under x/tools/go/analysis/cmd/vet https://github.com/golang/tools/tree/master/go/analysis/cmd/vet we can put this under the Unreleased milestone and it can get in at anytime.