A block with a single or expression needs to be treated as a comprehension instead of a
set/array with 1 item. e.g.: {1 | 1 }, [2 | foo]
Allow successfully parsing object comprehensions as rule body
x if { 1:2 | 1 }
fixes#306, fixes#307
Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>
