When we need to raise an error that is attached to a `syn` type (meaning the span of the error will correctly be associated with that type), this method is used. There is no actual `syn` error, we're just reporting a logic error of our own while processing some `syn` types.
(message: U, tokens: T)
source not stored for this graph (policy: none)
nothing calls this directly
no outgoing calls
no test coverage detected