Decode simple value (Bool or Nil).

src/cbor/decoder.cr

@@ -47,6 +47,14 @@ class CBOR::Decoder
     end
   end
 
+  def read_simple_value : Bool?
+    case token = @current_token
+    when Token::SimpleValueT
+      finish_token!
+      token.value.to_t
+    end
+  end
+
   def read_string : String
     case token = @current_token
     when Token::StringT

src/cbor/from_cbor.cr

@@ -218,13 +218,22 @@ end
 def Union.new(decoder : CBOR::Decoder)
   {% begin %}
     case decoder.current_token
-    {% if T.includes? Nil %}
+    {% if T.includes? Nil || T.includes? Bool %}
     when CBOR::Token::SimpleValueT
-      return decoder.read_nil
-    {% end %}
+      # This value could be either a boolean or nil.
+      value = decoder.read_simple_value
+      case value
       {% if T.includes? Bool %}
-    when CBOR::Token::SimpleValueT
-      return decoder.read_bool
+      when Bool
+        return value
+      {% end %}
+      {% if T.includes? Nil %}
+      when Nil
+        return nil
+      {% end %}
+      else
+        raise "value is neither Bool or Nil"
+      end
     {% end %}
     {% if T.includes? String %}
     when CBOR::Token::StringT