I am wondering why we can use a trailing d for double but we cannot use a trailing m for decimal in InlineData() below.

using System.Numerics;

public static class MathLib
{
    public static T Square<T>(T x) where T: INumber<T> => x * x;
}

public class MathLibTest
{
    [Theory]
    [InlineData(2.0d,4.0d)]
    public void DoubleTest(double x, double control)
    {
        var sut = MathLib.Square(x);
        Assert.Equal(sut, control);
    }

    [Theory]
    //[InlineData(2.0m, 4.0m)] // why can't we use a trailing m for decimal?
    [InlineData(2.0, 4.0)]
    public void DecimalTest(decimal x, decimal control)
    {
        var sut = MathLib.Square(x);
        Assert.Equal(sut, control);
    }
}