Pattern matching not doing expect type narrowing?

type TestType1 = {_tag:'Test1'}
type TestType2 = {_tag:'Test2'}

const testMatcher = Match.type<TestType1 | TestType2>().pipe(
  Match.discriminators('_tag')({
    Test1: ():number => 10,
    Test2: ():string => "Bar"
  }),
  Match.exhaustive
)

const test:TestType2 = {_tag:'Test2'}
const testInference = testMatcher(test)