x/text/language: matcher incorrect handling of zh

[diligiant]

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

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

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/frederic/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/frederic/.go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12.5/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12.5/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/frederic/Creative/src/wayke/backend/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/h9/05jw9tbx44941w86t3ml3bmw0000gn/T/go-build309324644=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Building on CLDR LocalMatcher tests, I tested the case where both zh-CN and zh-HK are supported and zh-TW is desired. I switched CN and HK relative positions in supported.

https://play.golang.org/p/4bG57qBzNQr

What did you expect to see?

I expected zh-HK to be returned in both cases.

What did you see instead?

zh-HK is returned when HK is before CN in supported, en is returned when CN precedes HK.

[ALTree]

Thanks for reporting this.

cc @mpvl for investigation.