Optimized version of Tuple#to_a (#8265)

spec/std/tuple_spec.cr

@@ -293,4 +293,13 @@ describe "Tuple" do
     ({/o+/, "bar"} === {"fox", "bar"}).should be_true
     ({1, 2} === nil).should be_false
   end
+
+  it "does to_a" do
+    ary = {1, 'a', true}.to_a
+    ary.should eq([1, 'a', true])
+    ary.size.should eq(3)
+
+    ary = Tuple.new.to_a
+    ary.size.should eq(0)
+  end
 end

src/tuple.cr

@@ -376,6 +376,15 @@ struct Tuple
     to_s
   end
 
+  def to_a
+    Array(Union(*T)).build(size) do |buffer|
+      {% for i in 0...T.size %}
+        buffer[{{i}}] = self[{{i}}]
+      {% end %}
+      size
+    end
+  end
+
   # Appends a string representation of this tuple to the given `IO`.
   #
   # ```