const github.com/google/go-cmp/cmp/internal/function.Transformer

2 uses

	github.com/google/go-cmp/cmp/internal/function (current package)
		func.go#L28: 	Transformer       = trFunc  // func(T) R

	github.com/google/go-cmp/cmp
		options.go#L279: 	if !function.IsType(v.Type(), function.Transformer) || v.IsNil() {