castKind
castKind:
| "ArrayToPointerDecay"
| "BitCast"
| "BuiltinFnToFnPtr"
| "Dependent"
| "FunctionToPointerDecay"
| "IntegralCast"
| "IntegralToBoolean"
| "IntegralToFloating"
| "LValueToRValue"
| "NoOp"
| "NullToPointer"
| "PointerToIntegral"
| "ToVoid"
Hexadecimal ID for the node, e.g. "0x..."