Generate methods for Swift, not just structs

Consider the following "hello world" proto:
https://github.com/grpc/grpc/blob/master/examples/protos/helloworld.proto

Compare the following commands:

1. java -jar wire-compiler-4.7.2-jar-with-dependencies.jar --proto_path=. --kotlin_out=. helloworld.proto
2. java -jar wire-compiler-4.7.2-jar-with-dependencies.jar --proto_path=. --swift_out=. helloworld.proto

Running the Kotlin version (1 above) generates the following four files:

HelloReply.kt
HelloRequest.kt
GreeterClient.kt
GrpcGreeterClient.kt

Running the Swift version (2 above), however, generates only:

HelloReply.swift
HelloRequest.swift

How to generate the two missing files for Swift also? (For example, a Swift protocol and a class or struct that conforms to that protocol, which contains Swift methods?) Otherwise all we have is models (structs). If it's not currently possible to generate Swift methods, what is the use case for the Swift Wire version in its current form?

Start with examples/protos/helloworld.proto and compare the Wire compiler's --kotlin_out and --swift_out behavior. Trace the Swift generator entry point to determine whether service methods are supported; done means Swift output includes equivalents of GreeterClient.kt and GrpcGreeterClient.kt, or the supported limitation is documented.