anchor.diff:                  result
   
   
  +
  +            let nextStage =
  +                match e.geometryShader with
  +                    | Some _ -> ShaderType.Geometry(None, OutputTopology.TriangleStrip)
  +                    | _ -> ShaderType.Fragment
  +
               let! tessUsed, tessCode = match e.tessControlShader, e.tessEvalShader with
                                           | None, None -> compile { return gsUsed, None }
                                           | Some tcs, Some tev ->
  
positive.code: 
              do! resetCompilerState
  
              let! vsCode = compile {
                              let vs = 
                                  match e.vertexShader with
  
negative.code:                                                 let newTcs = substitute tcs.body
                                                  let tcs = { tcs with body = newTcs }
  
                                                  let tcs = adjustToConfig config tcs (Some Vertex) (Some TessEval)
                                                  let tev = adjustToConfig config tev (Some TessControl) (Some nextStage)
  
  
                                                  let! tevc = compileShader "TEV" tev
  