flowchart TD
          IAstArg("IAstArg")

          IAstArg -->|"="| NullVerifierError_IAstArg_
          IAstFragment("IAstFragment")

          IAstFragment -->|"="| NullVerifierError_IAstFragment_
        

          flowchart TD
          IAstOperation("IAstOperation")

          IAstOperation -->|"="| VerifyOperation
          VerifyOperation("VerifyOperation")

          VerifyOperation -->|"_spreads"| IAstSpread
          VerifyOperation -->|"_usages"| IAstArg
          IAstSpread("IAstSpread")

          IAstSpread -->|"="| NullVerifierError_IAstSpread_
          IAstArg("IAstArg")

          IAstArg -->|"="| NullVerifierError_IAstArg_
          IAstVariable("IAstVariable")

          IAstVariable -->|"="| VerifyVariable
          ValueTuple_IAstArg_IAstVariable_("ValueTuple(IAstArg,IAstVariable)")

          ValueTuple_IAstArg_IAstVariable_ -->|"="| VerifyVariableUsage
          VerifyVariableUsage("VerifyVariableUsage")

          VerifyVariableUsage -->|"_definition"| IAstVariable
          VerifyVariableUsage -->|"_usage"| IAstArg
          IAstVariable("IAstVariable")

          IAstVariable -->|"="| VerifyVariable
          IAstArg("IAstArg")

          IAstArg -->|"="| NullVerifierError_IAstArg_
        

          flowchart TD
          ValueTuple_IAstSpread_IAstFragment_("ValueTuple(IAstSpread,IAstFragment)")

          ValueTuple_IAstSpread_IAstFragment_ -->|"="| VerifyFragmentUsage
          VerifyFragmentUsage("VerifyFragmentUsage")

          VerifyFragmentUsage -->|"_definition"| IAstFragment
          VerifyFragmentUsage -->|"_usage"| IAstSpread
          IAstFragment("IAstFragment")

          IAstFragment -->|"="| NullVerifierError_IAstFragment_
          IAstSpread("IAstSpread")

          IAstSpread -->|"="| NullVerifierError_IAstSpread_