namespace System
{
    public readonly struct Char : IComparable, IComparable<char>, IConvertible, IEquatable<char>, IFormattable, IParsable<char>, ISpanFormattable, ISpanParsable<char>, IUtf8SpanFormattable, IUtf8SpanParsable<char>, IAdditionOperators<char, char, char>, IAdditiveIdentity<char, char>, IBinaryInteger<char>, IBinaryNumber<char>, IBitwiseOperators<char, char, char>, IComparisonOperators<char, char, bool>, IDecrementOperators<char>, IDivisionOperators<char, char, char>, IEqualityOperators<char, char, bool>, IIncrementOperators<char>, IMinMaxValue<char>, IModulusOperators<char, char, char>, IMultiplicativeIdentity<char, char>, IMultiplyOperators<char, char, char>, INumber<char>, INumberBase<char>, IShiftOperators<char, int, char>, ISubtractionOperators<char, char, char>, IUnaryNegationOperators<char, char>, IUnaryPlusOperators<char, char>, IUnsignedNumber<char>
    {
        public static char ToUpper(char c);
    }
}