"No suitable Deconstruct instance or extension method was found" is incorrect

[gafter]

Compiling the following reports (among other things) that CS8129 No suitable Deconstruct instance or extension method was found for type 'IA', with 2 out parameters and a void return type.

using System;

class Program
{
    static void Main()
    {
        IA a = new A();
        (var x, var y) = a;
    }
}
interface I1
{
    void Deconstruct(out int X, out int Y);
}
interface I2
{
    void Deconstruct(out int X, out int Y);
}
interface IA : I1, I2 { }
class A : IA, I1, I2
{
    void I1.Deconstruct(out int X, out int Y) => (X, Y) = (3, 4);
    void I2.Deconstruct(out int X, out int Y) => (X, Y) = (7, 8);
}

However, there are indeed suitable Deconstruct instance methods for type IA. In fact there are too many of them. This diagnostic is simply incorrect.

[gafter]

See also #25533

[gafter]

Fixed in #31056