SA1500 false positive in stackalloc expression

[Tan90909090]

Version used: StyleCop.Analyzers 1.2.0-beta.66

using System;

class C
{
    static void Main()
    {
        Foo(stackalloc[] { 'a' }); // SA1500 is reported here
        Foo(new[] { 'a' }); // SA1500 is NOT reported here
    }

    static void Foo(ReadOnlySpan<char> a) { }
}

The Foo(stackalloc[] { 'a' }); code is in one line, so I think SA1500 should not be reported that.