to show unused block warning strictly. ```ruby class C def f = nil end class D def f = yield end [C.new, D.new].each{|obj| obj.f{}} ``` In this case, `D#f` accepts a block. However `C#f` doesn't accept a block. There are some cases passing a block with `obj.f{}` where `obj` is `C` or `D`. To avoid warnings on such cases, "unused block warning" will be warned only if there is not same name which accepts a block. On the above example, `C.new.f{}` doesn't show any warnings because there is a same name `D#f` which accepts a block. We call this default behavior as "relax mode". `strict_unused_block` new warning category changes from "relax mode" to "strict mode", we don't check same name methods and `C.new.f{}` will be warned. [Feature #15554]