diff --git a/lib/rubocop/ast/node.rb b/lib/rubocop/ast/node.rb
index b361ae655..b6d13f78b 100644
--- a/lib/rubocop/ast/node.rb
+++ b/lib/rubocop/ast/node.rb
@@ -464,11 +464,11 @@ def call_type?
       end
 
       def chained?
-        parent && parent.call_type? && eql?(parent.receiver)
+        parent&.call_type? && eql?(parent.receiver)
       end
 
       def argument?
-        parent && parent.send_type? && parent.arguments.include?(self)
+        parent&.send_type? && parent.arguments.include?(self)
       end
 
       def numeric_type?
diff --git a/lib/rubocop/ast/node/array_node.rb b/lib/rubocop/ast/node/array_node.rb
index d4f8835e0..8731440e7 100644
--- a/lib/rubocop/ast/node/array_node.rb
+++ b/lib/rubocop/ast/node/array_node.rb
@@ -22,7 +22,7 @@ def values
       #
       # @return [Boolean] whether the array is enclosed in square brackets
       def square_brackets?
-        loc.begin && loc.begin.is?('[')
+        loc.begin&.is?('[')
       end
 
       # Checks whether the `array` literal is delimited by percent brackets.
@@ -40,7 +40,7 @@ def percent_literal?(type = nil)
         if type
           loc.begin && loc.begin.source =~ PERCENT_LITERAL_TYPES[type]
         else
-          loc.begin && loc.begin.source.start_with?('%')
+          loc.begin&.source&.start_with?('%')
         end
       end
 
diff --git a/lib/rubocop/ast/node/block_node.rb b/lib/rubocop/ast/node/block_node.rb
index f37d67650..d049eaa03 100644
--- a/lib/rubocop/ast/node/block_node.rb
+++ b/lib/rubocop/ast/node/block_node.rb
@@ -50,14 +50,14 @@ def arguments?
       #
       # @return [Boolean] whether the `block` literal is enclosed in braces
       def braces?
-        loc.end && loc.end.is?('}')
+        loc.end&.is?('}')
       end
 
       # Checks whether the `block` literal is delimited by `do`-`end` keywords.
       #
       # @return [Boolean] whether the `block` literal is enclosed in `do`-`end`
       def keywords?
-        loc.end && loc.end.is?('end')
+        loc.end&.is?('end')
       end
 
       # The delimiters for this `block` literal.
diff --git a/lib/rubocop/ast/node/for_node.rb b/lib/rubocop/ast/node/for_node.rb
index b6c10aef6..18c64530d 100644
--- a/lib/rubocop/ast/node/for_node.rb
+++ b/lib/rubocop/ast/node/for_node.rb
@@ -17,7 +17,7 @@ def keyword
       #
       # @return [Boolean] whether the `for` node has a `do` keyword
       def do?
-        loc.begin && loc.begin.is?('do')
+        loc.begin&.is?('do')
       end
 
       # Checks whether this node body is a void context.
diff --git a/lib/rubocop/ast/node/hash_node.rb b/lib/rubocop/ast/node/hash_node.rb
index 40afbcc03..661cb7355 100644
--- a/lib/rubocop/ast/node/hash_node.rb
+++ b/lib/rubocop/ast/node/hash_node.rb
@@ -102,7 +102,7 @@ def mixed_delimiters?
       #
       # @return [Boolean] whether the `hash` literal is enclosed in braces
       def braces?
-        loc.end && loc.end.is?('}')
+        loc.end&.is?('}')
       end
     end
   end
diff --git a/lib/rubocop/ast/node/if_node.rb b/lib/rubocop/ast/node/if_node.rb
index c8bb187ed..45c79657a 100644
--- a/lib/rubocop/ast/node/if_node.rb
+++ b/lib/rubocop/ast/node/if_node.rb
@@ -103,7 +103,7 @@ def nested_conditional?
       #
       # @return [Boolean] whether the `if` node has at least one `elsif` branch
       def elsif_conditional?
-        else_branch && else_branch.if_type? && else_branch.elsif?
+        else_branch&.if_type? && else_branch&.elsif?
       end
 
       # Returns the branch of the `if` node that gets evaluated when its
diff --git a/lib/rubocop/ast/node/keyword_splat_node.rb b/lib/rubocop/ast/node/keyword_splat_node.rb
index 263a4791c..2c7c66304 100644
--- a/lib/rubocop/ast/node/keyword_splat_node.rb
+++ b/lib/rubocop/ast/node/keyword_splat_node.rb
@@ -8,7 +8,7 @@ module AST
     class KeywordSplatNode < Node
       include HashElementNode
 
-      DOUBLE_SPLAT = '**'.freeze
+      DOUBLE_SPLAT = '**'
 
       # This is used for duck typing with `pair` nodes which also appear as
       # `hash` elements.
diff --git a/lib/rubocop/ast/node/mixin/method_dispatch_node.rb b/lib/rubocop/ast/node/mixin/method_dispatch_node.rb
index f9a503b7e..0fd26765e 100644
--- a/lib/rubocop/ast/node/mixin/method_dispatch_node.rb
+++ b/lib/rubocop/ast/node/mixin/method_dispatch_node.rb
@@ -116,7 +116,7 @@ def double_colon?
       #
       # @return [Boolean] whether the receiver of this method dispatch is `self`
       def self_receiver?
-        receiver && receiver.self_type?
+        receiver&.self_type?
       end
 
       # Checks whether the *explicit* receiver of this method dispatch is a
@@ -125,7 +125,7 @@ def self_receiver?
       # @return [Boolean] whether the receiver of this method dispatch
       #                   is a `const` node
       def const_receiver?
-        receiver && receiver.const_type?
+        receiver&.const_type?
       end
 
       # Checks whether the method dispatch is the implicit form of `#call`,
@@ -140,7 +140,7 @@ def implicit_call?
       #
       # @return [Boolean] whether the dispatched method has a block
       def block_literal?
-        parent && parent.block_type? && eql?(parent.send_node)
+        parent&.block_type? && eql?(parent.send_node)
       end
 
       # Checks whether this node is an arithmetic operation
diff --git a/lib/rubocop/ast/node/mixin/method_identifier_predicates.rb b/lib/rubocop/ast/node/mixin/method_identifier_predicates.rb
index a0c25fe7b..7ddca670a 100644
--- a/lib/rubocop/ast/node/mixin/method_identifier_predicates.rb
+++ b/lib/rubocop/ast/node/mixin/method_identifier_predicates.rb
@@ -79,14 +79,14 @@ def camel_case_method?
       #
       # @return [Boolean] whether the receiver of this node is `self`
       def self_receiver?
-        receiver && receiver.self_type?
+        receiver&.self_type?
       end
 
       # Checks whether the *explicit* receiver of node is a `const` node.
       #
       # @return [Boolean] whether the receiver of this node is a `const` node
       def const_receiver?
-        receiver && receiver.const_type?
+        receiver&.const_type?
       end
 
       # Checks whether this is a negation method, i.e. `!` or keyword `not`.
diff --git a/lib/rubocop/ast/node/mixin/parameterized_node.rb b/lib/rubocop/ast/node/mixin/parameterized_node.rb
index 0ecb3afbc..9b26aca7e 100644
--- a/lib/rubocop/ast/node/mixin/parameterized_node.rb
+++ b/lib/rubocop/ast/node/mixin/parameterized_node.rb
@@ -10,7 +10,7 @@ module ParameterizedNode
       # @return [Boolean] whether this node's arguments are
       #                   wrapped in parentheses
       def parenthesized?
-        loc.end && loc.end.is?(')')
+        loc.end&.is?(')')
       end
 
       # A shorthand for getting the first argument of the node.
diff --git a/lib/rubocop/ast/node/mixin/predicate_operator_node.rb b/lib/rubocop/ast/node/mixin/predicate_operator_node.rb
index 1813976cd..43d635c34 100644
--- a/lib/rubocop/ast/node/mixin/predicate_operator_node.rb
+++ b/lib/rubocop/ast/node/mixin/predicate_operator_node.rb
@@ -5,10 +5,10 @@ module AST
     # Common functionality for nodes that are predicates:
     # `or`, `and` ...
     module PredicateOperatorNode
-      LOGICAL_AND  = '&&'.freeze
-      SEMANTIC_AND = 'and'.freeze
-      LOGICAL_OR   = '||'.freeze
-      SEMANTIC_OR  = 'or'.freeze
+      LOGICAL_AND  = '&&'
+      SEMANTIC_AND = 'and'
+      LOGICAL_OR   = '||'
+      SEMANTIC_OR  = 'or'
 
       # Returns the operator as a string.
       #
diff --git a/lib/rubocop/ast/node/pair_node.rb b/lib/rubocop/ast/node/pair_node.rb
index 47e6fa4ed..da2e34bea 100644
--- a/lib/rubocop/ast/node/pair_node.rb
+++ b/lib/rubocop/ast/node/pair_node.rb
@@ -8,10 +8,10 @@ module AST
     class PairNode < Node
       include HashElementNode
 
-      HASH_ROCKET = '=>'.freeze
-      SPACED_HASH_ROCKET = ' => '.freeze
-      COLON = ':'.freeze
-      SPACED_COLON = ': '.freeze
+      HASH_ROCKET = '=>'
+      SPACED_HASH_ROCKET = ' => '
+      COLON = ':'
+      SPACED_COLON = ': '
 
       # Checks whether the `pair` uses a hash rocket delimiter.
       #
diff --git a/lib/rubocop/ast/node/until_node.rb b/lib/rubocop/ast/node/until_node.rb
index 18f8af898..54f1783c8 100644
--- a/lib/rubocop/ast/node/until_node.rb
+++ b/lib/rubocop/ast/node/until_node.rb
@@ -28,7 +28,7 @@ def inverse_keyword
       #
       # @return [Boolean] whether the `until` node has a `do` keyword
       def do?
-        loc.begin && loc.begin.is?('do')
+        loc.begin&.is?('do')
       end
     end
   end
diff --git a/lib/rubocop/ast/node/when_node.rb b/lib/rubocop/ast/node/when_node.rb
index 1fd1c15e2..f94ab4402 100644
--- a/lib/rubocop/ast/node/when_node.rb
+++ b/lib/rubocop/ast/node/when_node.rb
@@ -39,7 +39,7 @@ def branch_index
       #
       # @return [Boolean] whether the `when` node has a `then` keyword
       def then?
-        loc.begin && loc.begin.is?('then')
+        loc.begin&.is?('then')
       end
 
       # Returns the body of the `when` node.
diff --git a/lib/rubocop/ast/node/while_node.rb b/lib/rubocop/ast/node/while_node.rb
index 154862042..61f46e95e 100644
--- a/lib/rubocop/ast/node/while_node.rb
+++ b/lib/rubocop/ast/node/while_node.rb
@@ -28,7 +28,7 @@ def inverse_keyword
       #
       # @return [Boolean] whether the `until` node has a `do` keyword
       def do?
-        loc.begin && loc.begin.is?('do')
+        loc.begin&.is?('do')
       end
     end
   end
diff --git a/lib/rubocop/node_pattern.rb b/lib/rubocop/node_pattern.rb
index 6f4f8d473..28bdd65ff 100644
--- a/lib/rubocop/node_pattern.rb
+++ b/lib/rubocop/node_pattern.rb
@@ -127,18 +127,18 @@ class Compiler
       PARAM     = /\A#{PARAM_NUMBER}\Z/.freeze
       CLOSING   = /\A(?:\)|\}|\])\Z/.freeze
 
-      REST      = '...'.freeze
-      CAPTURED_REST = '$...'.freeze
+      REST      = '...'
+      CAPTURED_REST = '$...'
 
       attr_reader :match_code, :tokens, :captures
 
       SEQ_HEAD_INDEX = -1
 
       # Placeholders while compiling, see with_..._context methods
-      CUR_PLACEHOLDER = '@@@cur'.freeze
-      CUR_NODE = "#{CUR_PLACEHOLDER} node@@@".freeze
-      CUR_ELEMENT = "#{CUR_PLACEHOLDER} element@@@".freeze
-      SEQ_HEAD_GUARD = '@@@seq guard head@@@'.freeze
+      CUR_PLACEHOLDER = '@@@cur'
+      CUR_NODE = "#{CUR_PLACEHOLDER} node@@@"
+      CUR_ELEMENT = "#{CUR_PLACEHOLDER} element@@@"
+      SEQ_HEAD_GUARD = '@@@seq guard head@@@'
 
       line = __LINE__
       ANY_ORDER_TEMPLATE = ERB.new <<-RUBY.strip_indent.gsub("-%>\n", '%>')
@@ -176,7 +176,7 @@ def run(node_var)
 
         @match_code = with_context(compile_expr, node_var, use_temp_node: false)
         @match_code.prepend("(captures = Array.new(#{@captures})) && ") \
-          if @captures > 0
+          if @captures.positive?
 
         fail_due_to('unbalanced pattern') unless tokens.empty?
       end
@@ -334,7 +334,7 @@ def compile_variadic_term
         def variadic_arity
           return unless @variadic_index
 
-          first = @variadic_index > 0 ? first_terms_arity : SEQ_HEAD_INDEX
+          first = @variadic_index.positive? ? first_terms_arity : SEQ_HEAD_INDEX
           yield first..-last_terms_arity - 1
         end
       end
diff --git a/lib/rubocop/processed_source.rb b/lib/rubocop/processed_source.rb
index 4b1f9a236..2741b7d87 100644
--- a/lib/rubocop/processed_source.rb
+++ b/lib/rubocop/processed_source.rb
@@ -7,7 +7,7 @@ module RuboCop
   # and other information such as disabled lines for cops.
   # It also provides a convenient way to access source lines.
   class ProcessedSource
-    STRING_SOURCE_NAME = '(string)'.freeze
+    STRING_SOURCE_NAME = '(string)'
 
     attr_reader :path, :buffer, :ast, :comments, :tokens, :diagnostics,
                 :parser_error, :raw_source, :ruby_version
@@ -157,7 +157,8 @@ def parse(source, ruby_version)
     def tokenize(parser)
       begin
         ast, comments, tokens = parser.tokenize(@buffer)
-        ast.complete! if ast
+
+        ast.respond_to?(:complete!) && ast.complete!
       rescue Parser::SyntaxError # rubocop:disable Lint/HandleExceptions
         # All errors are in diagnostics. No need to handle exception.
       end
@@ -170,9 +171,6 @@ def tokenize(parser)
     # rubocop:disable Metrics/MethodLength
     def parser_class(ruby_version)
       case ruby_version
-      when 2.2
-        require 'parser/ruby22'
-        Parser::Ruby22
       when 2.3
         require 'parser/ruby23'
         Parser::Ruby23
diff --git a/spec/rubocop/node_pattern_spec.rb b/spec/rubocop/node_pattern_spec.rb
index 937bd0e5d..a66fcf5f1 100644
--- a/spec/rubocop/node_pattern_spec.rb
+++ b/spec/rubocop/node_pattern_spec.rb
@@ -512,7 +512,7 @@
         end
 
         context 'on a node which meets all requirements of the second []' do
-          let(:ruby) { '2.2' }
+          let(:ruby) { '2.3' }
 
           it_behaves_like 'matching'
         end
diff --git a/spec/rubocop/processed_source_spec.rb b/spec/rubocop/processed_source_spec.rb
index e86332a18..e6144c191 100644
--- a/spec/rubocop/processed_source_spec.rb
+++ b/spec/rubocop/processed_source_spec.rb
@@ -98,7 +98,7 @@ def some_method
         # lacking an encoding comment will default to the external encoding,
         # which could for example be US-ASCII if the LC_ALL environment
         # variable is set to "C".
-        '号码 = 3'.dup.force_encoding('US-ASCII')
+        (+'号码 = 3').force_encoding('US-ASCII')
       end
 
       it 'is nil' do