anchor.diff:      new CallInstruction(),
       new EnterFunctionInstruction(),
       new ReturnInstruction(),
  -    new TypeConversionInstruction(NumberType.uint8, NumberType.uint16),
  -    new TypeConversionInstruction(NumberType.uint16, NumberType.uint32),
  -    new TypeConversionInstruction(NumberType.uint32, NumberType.uint64),
       new TypeConversionInstruction(NumberType.sint8, NumberType.sint16),
       new TypeConversionInstruction(NumberType.sint16, NumberType.sint32),
       new TypeConversionInstruction(NumberType.sint32, NumberType.sint64),
  -    new TypeConversionInstruction(NumberType.uint16, NumberType.uint8),
  -    new TypeConversionInstruction(NumberType.uint32, NumberType.uint16),
  -    new TypeConversionInstruction(NumberType.uint64, NumberType.uint32),
       new TypeConversionInstruction(NumberType.uint32, NumberType.fp32),
       new TypeConversionInstruction(NumberType.sint32, NumberType.fp32),
       new TypeConversionInstruction(NumberType.fp32, NumberType.uint32),
  
positive.code: 
  /// Converts the top stack element between the specified types. Instead of
  /// reinterpreting the memory, the value is retained. For example, executing a
  /// type conversion `double32↦uint32` on the value `1.0` yields `1` (which has
  /// a different bit pattern).
  ///
  /// The VM instruction set only supports the following subset of all to/from
  /// conversion pairs:
  ///
  /// integer width expansion – only conversion between adjacent sizes.
  ///
  ///     uint8↦uint16
  ///     uint16↦uint32
  ///     uint32↦uint64
  ///     sint8↦sint16
  ///     sint16↦sint32
  ///     sint32↦sint64
  ///
  /// integer width reduction – these simply crop the most significant bytes,
  /// which yields identical behaviour for signed and unsigned values.
  ///
  ///     uint16↦uint8
  ///     uint32↦uint16
  ///     uint64↦uint32
  ///
  /// int / float conversion – only between same-size types.
  ///
  ///     uint32↦float
  ///     sint32↦float
  
negative.code: ///     double↦uint64
  ///     double↦sint64
  ///
  /// and float/double conversion.
  ///
  ///     float↦double
  ///     double↦float
  