Add Slice#same?

spec/std/slice_spec.cr

@@ -489,6 +489,20 @@ describe "Slice" do
     end
   end
 
+  it "#same?" do
+    slice = Slice[1, 2, 3]
+
+    slice.should be slice
+    slice.should_not be slice.dup
+    slice.should_not be Slice[1, 2, 3]
+
+    (slice + 1).should be slice + 1
+    slice.should_not be slice + 1
+
+    (slice[0, 2]).should be slice[0, 2]
+    slice.should_not be slice[0, 2]
+  end
+
   it "does macro []" do
     slice = Slice[1, 'a', "foo"]
     slice.should be_a(Slice(Int32 | Char | String))

src/slice.cr

@@ -845,6 +845,21 @@ struct Slice(T)
     {% end %}
   end
 
+  # Returns `true` if `self` and *other* point to the same memory, i.e. pointer
+  # and size are identical.
+  #
+  # ```
+  # slice = Slice[1, 2, 3]
+  # slice.same?(slice)           # => true
+  # slice == Slice[1, 2, 3]      # => false
+  # slice.same?(slice + 1)       # => false
+  # (slice + 1).same?(slice + 1) # => true
+  # slice.same?(slice[0, 2])     # => false
+  # ```
+  def same?(other : self) : Bool
+    to_unsafe == other.to_unsafe && size == other.size
+  end
+
   def to_slice : self
     self
   end

src/spec/expectations.cr

@@ -65,11 +65,19 @@ module Spec
     end
 
     def failure_message(actual_value)
-      "Expected: #{@expected_value.pretty_inspect} (object_id: #{@expected_value.object_id})\n     got: #{actual_value.pretty_inspect} (object_id: #{actual_value.object_id})"
+      "Expected: #{@expected_value.pretty_inspect} (#{identify(@expected_value)})\n     got: #{actual_value.pretty_inspect} (#{identify(actual_value)})"
     end
 
     def negative_failure_message(actual_value)
-      "Expected: value.same? #{@expected_value.pretty_inspect} (object_id: #{@expected_value.object_id})\n     got: #{actual_value.pretty_inspect} (object_id: #{actual_value.object_id})"
+      "Expected: #{@expected_value.pretty_inspect} (#{identify(@expected_value)})\n     got: #{actual_value.pretty_inspect} (#{identify(actual_value)})"
+    end
+
+    private def identify(value)
+      if value.responds_to?(:object_id)
+        "object_id: #{value.object_id}"
+      else
+        value.to_unsafe
+      end
     end
   end