Fix RDoc::Attr#add_alias handling of aliased attribute accessor (#1605)

Ensure aliased attr_accessor attributes have the correct access type
('R' or 'W') instead of always being 'RW'.

For more details on the issue being addressed, see
#1286 (comment).

Author: extern-c

lib/rdoc/code_object/attr.rb

@@ -43,7 +43,8 @@ def ==(other)
   # Add +an_alias+ as an attribute in +context+.
 
   def add_alias(an_alias, context)
-    new_attr = self.class.new(text, an_alias.new_name, rw, comment, singleton: singleton)
+    access_type = an_alias.new_name.end_with?('=') ? 'W' : 'R'
+    new_attr = self.class.new(text, an_alias.new_name, access_type, comment, singleton: singleton)
     new_attr.record_location an_alias.file
     new_attr.visibility = self.visibility
     new_attr.is_alias_for = self

test/rdoc/code_object/attr_test.rb

@@ -187,4 +187,18 @@ def test_type
     assert_equal 'class', @a.type
   end
 
+  [
+    ['bar', 'baz', 'R'],
+    ['bar=', 'baz=', 'W']
+  ].each do |original_name, new_name, expected_rw|
+    define_method("test_add_alias_#{new_name}_for_an_attribute_accessor") do
+      context = RDoc::Context.new
+      attr = RDoc::Attr.new nil, 'bar', 'RW', ''
+      an_alias = RDoc::Alias.new nil, original_name, new_name, ''
+
+      new_attr = attr.add_alias an_alias, context
+
+      assert_equal expected_rw, new_attr.rw
+    end
+  end
 end