func google.golang.org/protobuf/reflect/protoreflect.isLetter

3 uses

	google.golang.org/protobuf/reflect/protoreflect (current package)
		proto.go#L466: 	if len(s) == 0 || !isLetter(s[i]) {
		proto.go#L475: func isLetter(c byte) bool {
		proto.go#L479: 	return isLetter(c) || ('0' <= c && c <= '9')