in Sources/SIL/SILPrinter.swift [356:370]
func print(_ convention: Convention) {
print("(")
switch convention {
case .c:
print("c")
case .method:
print("method")
case .thin:
print("thin")
case let .witnessMethod(type):
print("witness_method: ")
naked(type)
}
print(")")
}