[perl #126532] [BUG] Internal error when passing whitespace through a named argument in Rakudo

The examples would fail usage constraints with the parameterless MAIN.
I could not get them to fail with any internal messages on current rakudo,
either with the parameterless MAIN or with a MAIN that had a :$y.

Haven't looked as to when this got fixed.

Tests added for both cases (though I had to add a sub USAGE when testing
the parameterless case) in https://github.com/perl6/roast/commit/bdf67b698b,
so closing as resolved.