Add spaceship operator to StaticArray (#11364)

spec/std/static_array_spec.cr

@@ -63,6 +63,16 @@ describe "StaticArray" do
     end
   end
 
+  describe "<=>" do
+    it "correctly compares two static arrays" do
+      array1 = StaticArray(Int32, 3).new(5)
+      array2 = StaticArray(Int32, 3).new(7)
+      (array1 <=> array2).should be < 0
+      (array2 <=> array1).should be > 0
+      (array1 <=> array1).should eq 0
+    end
+  end
+
   describe "values_at" do
     it "returns the given indexes" do
       StaticArray(Int32, 4).new { |i| i + 1 }.values_at(1, 0, 2).should eq({2, 1, 3})

src/static_array.cr

@@ -33,6 +33,7 @@
 # doesn't specify a type but a size. Its value can be an `Int32` literal or
 # constant.
 struct StaticArray(T, N)
+  include Comparable(StaticArray)
   include Indexable::Mutable(T)
 
   # Creates a new `StaticArray` with the given *args*. The type of the
@@ -113,6 +114,10 @@ struct StaticArray(T, N)
     false
   end
 
+  def <=>(other : StaticArray)
+    to_slice <=> other.to_slice
+  end
+
   @[AlwaysInline]
   def unsafe_fetch(index : Int) : T
     to_unsafe[index]