diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b96a61d5f..172ef353b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -28,3 +28,14 @@ jobs:
           bundle exec rake
         env:
           CI: true
+  build_ruby3:
+    name: "Ruby: 3.0 OS: Linux"
+    container: ruby:3.0-rc-alpine
+    steps:
+      - uses: actions/checkout@v2
+      - run: apk add -U build-base
+      - run: gem update --system --no-document --conservative
+      - run: bundle install --jobs=3 --retry=3
+      - run: ruby -v && bundle exec rake
+        env:
+          CI: true
diff --git a/Gemfile b/Gemfile
index f10f5256b..67f06391d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,7 @@ group :development do
   gem 'simplecov'
   gem 'samus', '~> 3.0.9', :require => false
   gem 'coveralls', :require => false
+  gem 'webrick'
 end
 
 group :asciidoc do
diff --git a/lib/yard/templates/section.rb b/lib/yard/templates/section.rb
index e8674efe5..ca42adddc 100644
--- a/lib/yard/templates/section.rb
+++ b/lib/yard/templates/section.rb
@@ -20,9 +20,7 @@ def dup
 
       def [](*args)
         if args.first.is_a?(Range) || args.size > 1
-          obj = super(*args)
-          obj.name = name
-          return obj
+          return self.class.new(name, *super(*args))
         elsif args.first.is_a?(Integer)
           return super(*args)
         end
diff --git a/rbs b/rbs
new file mode 160000
index 000000000..4e5ee848b
--- /dev/null
+++ b/rbs
@@ -0,0 +1 @@
+Subproject commit 4e5ee848b318c6c9cd4131a825f0b794017acb3a
diff --git a/spec/parser/ruby/ruby_parser_spec.rb b/spec/parser/ruby/ruby_parser_spec.rb
index f4eb09878..ffd3d41bb 100644
--- a/spec/parser/ruby/ruby_parser_spec.rb
+++ b/spec/parser/ruby/ruby_parser_spec.rb
@@ -539,5 +539,16 @@ class B
         is_expected.to eq "#{condition_type} condition?; 42; end"
       end
     end
+
+    it "handles single-line method declaration syntax" do
+      YARD.parse_string <<-eof
+        class A
+          # Adds two numbers
+          def add(x) = x + 1
+        end
+      eof
+
+      expect(Registry.at('A#add').docstring).to eq('Adds two numbers')
+    end if RUBY_VERSION >= '3.'
   end
 end if HAVE_RIPPER
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index c59b2d99e..9c521a1fd 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -209,4 +209,5 @@ def puts(str = '')
   Kernel.srand config.seed
 end
 
+YARD::Logger
 include YARD
diff --git a/spec/templates/helpers/html_helper_spec.rb b/spec/templates/helpers/html_helper_spec.rb
index f98f40c0a..5f3f268a5 100644
--- a/spec/templates/helpers/html_helper_spec.rb
+++ b/spec/templates/helpers/html_helper_spec.rb
@@ -21,27 +21,22 @@ def options
   end
 
   describe "#charset" do
+    after { Encoding.default_external = 'utf-8' if defined?(Encoding) }
+
     it "returns foo if LANG=foo" do
       expect(ENV).to receive(:[]).with('LANG').and_return('shift_jis') if YARD.ruby18?
-      expect(Encoding.default_external).to receive(:name).and_return('shift_jis') if defined?(Encoding)
+      Encoding.default_external = 'shift_jis' if defined?(Encoding)
       expect(charset).to eq 'shift_jis'
     end
 
-    ['US-ASCII', 'ASCII-7BIT', 'ASCII-8BIT'].each do |type|
+    ['US-ASCII', 'binary', 'ASCII-8BIT'].each do |type|
       it "converts #{type} to iso-8859-1" do
         expect(ENV).to receive(:[]).with('LANG').and_return(type) if YARD.ruby18?
-        expect(Encoding.default_external).to receive(:name).and_return(type) if defined?(Encoding)
+        Encoding.default_external = type if defined?(Encoding)
         expect(charset).to eq 'iso-8859-1'
       end
     end
 
-    it "supports utf8 as an encoding value for utf-8" do
-      type = 'utf8'
-      expect(ENV).to receive(:[]).with('LANG').and_return(type) if YARD.ruby18?
-      expect(Encoding.default_external).to receive(:name).and_return(type) if defined?(Encoding)
-      expect(charset).to eq 'utf-8'
-    end
-
     it "takes file encoding if there is a file" do
       @file = OpenStruct.new(:contents => String.new('foo').force_encoding('sjis'))
       # not the correct charset name, but good enough
diff --git a/yard-rbs-core b/yard-rbs-core
new file mode 160000
index 000000000..7d9654fac
--- /dev/null
+++ b/yard-rbs-core
@@ -0,0 +1 @@
+Subproject commit 7d9654facdd61c26eee517c0e410081727d28181