Incorrect deconstruction of foreach item

[mmusu3]

Input code

static class DeconstructForeachItemTest
{
    static void Test(Dictionary<string, object> data)
    {
        var dictionary = new Dictionary<string, object>();

        foreach (var (key, value) in data)
        {
            dictionary[key] = value;
        }
    }

    static void Deconstruct<K, V>(this KeyValuePair<K, V> pair, out K k, out V v)
    {
        k = pair.Key;
        v = pair.Value;
    }
}

Erroneous output

internal static class DeconstructForeachItemTest
{
    private static void Test(Dictionary<string, object> data)
    {
        Dictionary<string, object> dictionary = new Dictionary<string, object>();
        foreach (KeyValuePair<string, object> datum in data)
        {
            string key;
            (key, dictionary[key]) = datum;
        }
    }

    private static void Deconstruct<K, V>(this KeyValuePair<K, V> pair, out K k, out V v)
    {
        k = pair.Key;
        v = pair.Value;
    }
}

Error CS0165: Use of unassigned local variable 'key'

Details

• ILSpy version 7.0.0.6372-preview3

[siegfriedpammer]

Fixing #2378 improves this somewhat as now this does no longer produce invalid code, however, the deconstruction is no longer detected, most likely because of the inline assignment.

// DeconstructForeachItemTest
using System.Collections.Generic;

private static void Test(Dictionary<string, object> data)
{
    Dictionary<string, object> dictionary = new Dictionary<string, object>();
    foreach (KeyValuePair<string, object> datum in data)
    {
        datum.Deconstruct(out var key2, out var value2);
        string key = key2;
        object value = (dictionary[key] = value2);
    }
}

[mmusu3]

The fixes only seem to apply for projects targeting newer .NET versions (tested with Core 3.1 and Net 5). It still produces the old wrong output for older versions (tested with netstandard2 and netfx 4.8).