[bug] typecheck report doest not match for duck type #call

[SolaWing]

# @return [#call]
def foo
  -> {}
end
# @return [#call]
def bar # --> [Typecheck] [E] Declared return type #call does not match inferred type #call for #bar
  foo
end

[castwide]

Interestingly, I was able to reproduce this error using 0.44.2, but not in the master branch. I suspect that the fix for #497 coincidentally fixed this one, too. I'll write a test to confirm.