DenseMatrix<T>.GetHashCode is incorrect

[antonfirsov]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

Description

DenseMatrix<T> equality + hash code is incorrect:

       public bool Equals(DenseMatrix<T> other) =>
            this.Columns == other.Columns
            && this.Rows == other.Rows
            && this.Span.SequenceEqual(other.Span);

        /// <inheritdoc/>
        public override int GetHashCode() => this.Data.GetHashCode();

For matrices having same content but different arrays a.Equals(b) == true, but a.GetHashCode() != b.GetHashCode(), which is a bug.

[JimBobSquarePants]

For matrices having same content but different arrays

What do you mean by this? I don't understand.

I see the issue now.