Alias @value to @exception in Try::Error (#177)

* Alias @value to @exception in Try::Error

This allows deconstruct to work correctly

* Update try_spec.rb to test deconstruction

* Move pattern match tests from unit to integration specs

lib/dry/monads/try.rb

@@ -186,7 +186,7 @@ class Error < Try
         def initialize(exception)
           super()
 
-          @exception = exception
+          @exception = @value = exception
         end
 
         # @return [String]

spec/integration/pattern_matching_spec.rb

@@ -1,6 +1,57 @@
 # frozen_string_literal: true
 
 RSpec.describe "pattern matching" do
+  describe "Dry::Monads::Try" do
+    include Dry::Monads[:try]
+
+    context "Value" do
+      it "matches on the singleton array of the value when value is not an array" do
+        expect(
+          (Value(1) in [1])
+        ).to be(true)
+      end
+
+      it "matches on the value when value is an array" do
+        expect(
+          (Value([1]) in [1])
+        ).to be(true)
+      end
+
+      it "matches on the empty array when value is Unit" do
+        expect(
+          (Value(Dry::Monads::Unit) in [])
+        ).to be(true)
+      end
+
+      it "matches on the value's keys when value acts like a hash" do
+        expect(
+          (Value({code: 101, foo: :bar}) in { code: 101 })
+        ).to be(true)
+      end
+
+      it "matches on the empty hash when value doesn't act like a hash" do
+        expect(
+          (Value(:foo) in {})
+        ).to be(true)
+      end
+    end
+
+    context "Error" do
+      it "matches on the singleton array of the exception" do
+        exception = StandardError.new("boom")
+        failure = Try { raise exception }
+
+        expect(
+          (failure in [exception])
+        ).to be(true)
+
+        expect(
+          (failure in Dry::Monads::Try::Error(exception))
+        ).to be(true)
+      end
+    end
+  end
+
   describe "Dry::Monads::Result" do
     include Dry::Monads[:result]