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capnproto

Forward declarations in CapnProto

In a CapnProto schema is there any way to forward-declare structs so you can make a tree structure like this:

struct ExecuteProgram {
  code @0 :Text;
}

struct SequenceProgram {
  programs @0 :List(Program)
}

struct IfProgram {
  condition @1 :Program;
  trueBody @2 :Program;
  falseBody @3 :Program;
}

struct Program {
  union {
    execute @0 :ExecuteProgram;
    sequence @1 :SequenceProgram;
    if @2 :IfProgram;
  }
}

If I try to compile this the compiler gives the very helpful error message Parse error. I assume it is complaining because I use Program before it is declared.

Is there any way around this?

Solution

  • It turns out you don't need forward declarations, I was just missing a semicolon. What was I saying about Parse error being a terrible error message?