[perl #120071] Losing type info in the bowels of MapIter

[Christian Bartolomaeus via RT]

The type info for deleted elements is not lost anymore:

$ perl6-m -e 'my Int @a=^3; @a[1]:delete; @a.map:{say .WHAT.perl }; 
@a[1].WHAT.perl.say'
Int
Int
Int
Int

I added a test to S09-typed-arrays/arrays.t with commit 
https://github.com/perl6/roast/commit/4ec7087158

I'm closing this ticket as 'resolved'.