1 files changed, 24 insertions, 6 deletions
diff --git a/lib/diff/lcs/block.rb b/lib/diff/lcs/block.rb
index 430702d..d31a4d3 100644
--- a/lib/diff/lcs/block.rb
+++ b/lib/diff/lcs/block.rb
@@ -1,15 +1,31 @@
 # frozen_string_literal: true
+# typed: strict
 
 # A block is an operation removing, adding, or changing a group of items.
 # Basically, this is just a list of changes, where each change adds or
 # deletes a single item. Used by bin/ldiff.
 class Diff::LCS::Block
-  attr_reader :changes, :insert, :remove
+  extend T::Sig
 
+  ArrayOfChange = T.type_alias { T::Array[Diff::LCS::Change] }
+
+  # The full set of changes in the block.
+  sig { returns(ArrayOfChange) }
+  attr_reader :changes
+
+  # The insertions in the block.
+  sig { returns(ArrayOfChange) }
+  attr_reader :insert
+
+  # The deletions in the block.
+  sig { returns(ArrayOfChange) }
+  attr_reader :remove
+
+  sig { params(chunk: ArrayOfChange).void }
   def initialize(chunk)
-    @changes = []
-    @insert = []
-    @remove = []
+    @changes = T.let([], ArrayOfChange)
+    @insert = T.let([], ArrayOfChange)
+    @remove = T.let([], ArrayOfChange)
 
     chunk.each do |item|
       @changes << item
@@ -18,12 +34,14 @@ class Diff::LCS::Block
     end
   end
 
+  sig { returns(Integer) }
   def diff_size
-    @insert.size - @remove.size
+    insert.size - remove.size
   end
 
+  sig { returns(String) }
   def op
-    case [@remove.empty?, @insert.empty?]
+    case [remove.empty?, insert.empty?]
     when [false, false]
       '!'
     when [false, true]