Sorbet sample

sorbet_sample.rb

# typed: strong

class SorbetSample
  sig { params(array: T::Array[MyInteger]).void }
  def initialize(array)
    @array = T.let(array, T::Array[MyInteger])
  end

  sig { returns(Integer) }
  def use_array_of_premitive_types
    array = T.let([1,2,3], T::Array[Integer])
    array.reduce(0) do |memo, item|
      memo + item
    end
  end

  sig { returns(MyInteger) }
  def use_array_of_self_defined_types
    array = T.let(
      [
        MyInteger.new(1),
        MyInteger.new(2),
        MyInteger.new(3),
      ],
      T::Array[MyInteger]
    )

    array.reduce(MyInteger.new(0)) do |memo, item|
      memo + item
    end
  end

  sig { returns(MyInteger) }
  def use_instance_variables
    @array.reduce(MyInteger.new(0)) do |memo, item|
      memo + item
    end
  end

  # ここより上は静的検査できてるっぽい

  # これができない
  sig { returns(MyInteger) }
  def use_another_self_defined_type
    array = T.let(
      [
        MyStruct.new(n: MyInteger.new(1)),
        MyStruct.new(n: MyInteger.new(2)),
        MyStruct.new(n: MyInteger.new(3)),
      ],
      T::Array[MyStruct]
    )

    array.reduce(MyInteger.new(0)) do |memo, item|
      memo + item.n
    end
  end

  # これならできる (reduce -> each)
  sig { returns(MyInteger) }
  def use_another_self_defined_type2
    array = T.let(
      [
        MyStruct.new(n: MyInteger.new(1)),
        MyStruct.new(n: MyInteger.new(2)),
        MyStruct.new(n: MyInteger.new(3)),
      ],
      T::Array[MyStruct]
    )

    sum = MyInteger.new(0)
    array.each do |item|
      sum = sum + item.n
    end
    sum
  end
end

class MyInteger
  sig { returns(Integer) }
  attr_reader :value

  sig { params(value: Integer).void }
  def initialize(value)
    @value = T.let(value, Integer)
  end

  sig { params(another: MyInteger).returns(MyInteger) }
  def +(another)
    MyInteger.new(@value + another.value)
  end
end

class MyStruct
  sig { returns(MyInteger) }
  attr_reader :n

  sig { params(n: MyInteger).void }
  def initialize(n:)
    @n = T.let(n, MyInteger)
  end
end

# lib/sorbet_sample.rb:54: This code is untyped https://srb.help/7018
#     54 |    array.reduce(MyInteger.new(0)) do |memo, item|
#     55 |      memo + item.n
#     56 |    end
#
# lib/sorbet_sample.rb:54: This code is untyped https://srb.help/7018
#     54 |    array.reduce(MyInteger.new(0)) do |memo, item|
#                                                ^^^^
#
# lib/sorbet_sample.rb:54: This code is untyped https://srb.help/7018
#     54 |    array.reduce(MyInteger.new(0)) do |memo, item|
#                                                      ^^^^
#
# lib/sorbet_sample.rb:55: This code is untyped https://srb.help/7018
#     55 |      memo + item.n
#                      ^^^^^^
#
# lib/sorbet_sample.rb:55: This code is untyped https://srb.help/7018
#     55 |      memo + item.n
#               ^^^^^^^^^^^^^
# Errors: 5

memo と item は同じ型じゃないといけない感じですね。（初歩的でした…

これでいけた。

diff --git a/lib/sorbet_sample.rb b/lib/sorbet_sample.rb
index ac7c8a5..b91fd08 100644
--- a/lib/sorbet_sample.rb
+++ b/lib/sorbet_sample.rb
@@ -50,8 +50,8 @@ class SorbetSample
       T::Array[MyStruct]
     )

-    array.reduce(MyInteger.new(0)) do |memo, item|
-      memo + item.n
+    array.map(&:n).reduce(MyInteger.new(0)) do |memo, item|
+      memo + item
     end
   end

array.map(&:n).reduce(MyInteger.new(0), :+)

だとダメ。

lib/sample.rb:53: This code is untyped https://srb.help/7018
    53 |    array.map(&:n).reduce(MyInteger.new(0), :+)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Errors: 1

こうなる。 😿