C#•15mo ago

❔ Unable to box custom value type

Hiya, I'm writing a library to interact with MIDI files. I'm laying down some framework stuff (seven bit numbers, Variable Length Quantities [VLQ] etc.), the VLQ's and seven bit numbers are implemented as structs currently.

using System;
using MidiLibrary.Util;

namespace MidiLibrary.Structures
{
    public readonly struct VariableLengthQuantity
    //TODO: Override ToString
    {
        private readonly bool[][] Number { get; init; }

        private VariableLengthQuantity(long number)
        {
            bool[] binaryRep = BinaryTools.LongToBinary(number);
            bool[][] sevenBitNumbers = BinaryTools.BinaryToSevenBitNumbers(binaryRep);
            // Reverse the array
            Array.Reverse(sevenBitNumbers, 0, sevenBitNumbers.Length);
            
            for (int i = 0; i < sevenBitNumbers.Length; i++)
            {
                sevenBitNumbers[i] = BinaryTools.PadBinary(sevenBitNumbers[i], 8);
                // everything that isn't next, has a 1 (true) as MSB
                sevenBitNumbers[i][^1] = true;
            }

            sevenBitNumbers[0][^1] = false;

            this.Number = sevenBitNumbers;
        }
        
        public static explicit operator VariableLengthQuantity(long number) => new VariableLengthQuantity(number);

        private static byte[] FromLong(long number)
        {
            throw new NotImplementedException();
        }

        private static long ToLong(byte[] array)
        {
            throw new NotImplementedException();
        }
    }
}

using System;
using MidiLibrary.Util;

namespace MidiLibrary.Structures
{
    public readonly struct VariableLengthQuantity
    //TODO: Override ToString
    {
        private readonly bool[][] Number { get; init; }

        private VariableLengthQuantity(long number)
        {
            bool[] binaryRep = BinaryTools.LongToBinary(number);
            bool[][] sevenBitNumbers = BinaryTools.BinaryToSevenBitNumbers(binaryRep);
            // Reverse the array
            Array.Reverse(sevenBitNumbers, 0, sevenBitNumbers.Length);
            
            for (int i = 0; i < sevenBitNumbers.Length; i++)
            {
                sevenBitNumbers[i] = BinaryTools.PadBinary(sevenBitNumbers[i], 8);
                // everything that isn't next, has a 1 (true) as MSB
                sevenBitNumbers[i][^1] = true;
            }

            sevenBitNumbers[0][^1] = false;

            this.Number = sevenBitNumbers;
        }
        
        public static explicit operator VariableLengthQuantity(long number) => new VariableLengthQuantity(number);

        private static byte[] FromLong(long number)
        {
            throw new NotImplementedException();
        }

        private static long ToLong(byte[] array)
        {
            throw new NotImplementedException();
        }
    }
}

This is the boxing allocation I'm trying to use:

VariableLengthQuantity a = (VariableLengthQuantity) 137;
object aa = a;

VariableLengthQuantity a = (VariableLengthQuantity) 137;
object aa = a;

Full disclosure, I'm pretty new to using structs. I'd normally just throw it into a class but figure I should probably branch out to something better. Boxing allocation: conversion from 'VariableLengthQuantity' to 'object' requires boxing of value type

5 Replies

Eyrim•15mo ago

(also goes without saying this isn't refactored or anything yet, I literally just wrote it)

basically, i am little cat•15mo ago

Probably something related to (customized or modified) compiler/framework/plugin/whatever. https://discord.com/channels/143867839282020352/251386218351165441/1100797762901131376 Here it compiles fine

MODiX•15mo ago

basically, i am little cat#5356

REPL Result: Success

public readonly struct Foo {
    private readonly bool[][] bar;
}

var a = default(Foo);
object b = a;
b

public readonly struct Foo {
    private readonly bool[][] bar;
}

var a = default(Foo);
object b = a;
b

Result: Foo

{}

{}

Quoted by

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Compile: 481.937ms | Execution: 30.878ms | React with ❌ to remove this embed.

Eyrim•15mo ago

huh, weird because i was thinking like "this is fine, it's boxed, stop complaining" but yeah that makes sense that it's something in my env tysm <33

Accord•15mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Unable to box custom value type