Incorrect return type error with tuple return type within loop with conditional logic

[Blacksmoke16]

Bug Report

nodes = ["a", "b", "c"]

def foo(nodes) : {String, Int32}?
  nodes.each do |node|
    if node.is_a?(String) && (branches = conditional_statement_branches node) > 1
      return node, branches
    end
  end
end

private def conditional_statement_branches(node) : Int32
  2
end

pp foo nodes

Results in:

Error: method ::foo must return (Tuple(String, Int32) | Nil) but it is returning Tuple(String, Int32 | Nil)

Why does it think branches could be nil?

[yxhuvud]

And also, why does it think the not-matching case doesn't exist. I'm guessing the answers are related to each other.

[HertzDevil]

Reduced:

typeof(1 && (x = 1) == 1 ? x : 'a') # => (Char | Int32 | Nil)