Remove useless Tuple from chain
Remove cases where an array is used in a boolean context
Merge pull request #1727 from yebblies/issue4733

Remove cases where an array is used in a boolean context
import std.typecons outside unittests since it is needed
Merge pull request #1728 from adamdruppe/std_uni_compile_error

import std.typecons outside unittests since it is needed
Merge pull request #1723 from monarchdodra/chainTuple

Remove useless Tuple from chain