Fix an error for Lint/MixedRegexpCaptureTypes cop

This commit fixes the following error.

```console
% cd repo/to/rubocop-hq/rubocop
% bundle exec rubocop -d --only Lint/MixedRegexpCaptureTypes
lib/rubocop/cop/utils/format_string.rb
For /Users/koic/src/github.com/rubocop-hq/rubocop: configuration from
/Users/koic/src/github.com/rubocop-hq/rubocop/.rubocop.yml
configuration from
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rubocop-performance-1.6.0/config/default.yml
configuration from
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rubocop-performance-1.6.0/config/default.yml
Default configuration from
/Users/koic/src/github.com/rubocop-hq/rubocop/config/default.yml
configuration from
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rubocop-rspec-1.39.0/config/default.yml
configuration from
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/rubocop-rspec-1.39.0/config/default.yml
Inheriting configuration from
/Users/koic/src/github.com/rubocop-hq/rubocop/.rubocop_todo.yml
Inspecting 1 file
Scanning
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/utils/format_string.rb
An error occurred while Lint/MixedRegexpCaptureTypes cop was inspecting
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/utils/format_string.rb:18:19.
No valid target found for '*'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/parser.rb:432:in
`quantifier'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/parser.rb:102:in
`parse_token'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/parser.rb:39:in
`block in parse'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/lexer.rb:55:in
`block in lex'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/lexer.rb:55:in
`map'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/lexer.rb:55:in
`lex'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/lexer.rb:15:in
`lex'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/parser.rb:38:in
`parse'
/Users/koic/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/regexp_parser-1.7.0/lib/regexp_parser/parser.rb:22:in
`parse'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/lint/mixed_regexp_capture_types.rb:28:in
`on_regexp'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:56:in
`block (2 levels) in trigger_responding_cops'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:115:in
`with_cop_error_handling'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:55:in
`block in trigger_responding_cops'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:54:in
`each'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:54:in
`trigger_responding_cops'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/cop/commissioner.rb:32:in
`block (2 levels) in <class:Commissioner>'
```

RuboCop does not know a value of variables that it will contain in the regexp literal.
For example, `/(?<foo>#{var}*)` is interpreted as `/(?<foo>*)`.
So it does not offense when variables are used in regexp literals.

Also this PR fixes regexps that is causing an error in `regexp_parser` gem.

lib/rubocop/cop/lint/mixed_regexp_capture_types.rb

@@ -25,6 +25,8 @@ class MixedRegexpCaptureTypes < Cop
               'in a Regexp literal.'
 
         def on_regexp(node)
+          return if contain_non_literal?(node)
+
           tree = Regexp::Parser.parse(node.content)
           return unless named_capture?(tree)
           return unless numbered_capture?(tree)
@@ -34,6 +36,15 @@ def on_regexp(node)
 
         private
 
+        def contain_non_literal?(node)
+          if node.respond_to?(:type) && (node.variable? || node.send_type? || node.const_type?)
+            return true
+          end
+          return false unless node.respond_to?(:children)
+
+          node.children.any? { |child| contain_non_literal?(child) }
+        end
+
         def named_capture?(tree)
           tree.each_expression.any? do |e|
             e.instance_of?(Regexp::Expression::Group::Capture)

lib/rubocop/cop/style/redundant_percent_q.rb

@@ -27,7 +27,7 @@ class RedundantPercentQ < Cop
         EMPTY = ''
         PERCENT_Q = '%q'
         PERCENT_CAPITAL_Q = '%Q'
-        STRING_INTERPOLATION_REGEXP = /#\{.+}/.freeze
+        STRING_INTERPOLATION_REGEXP = /#\{.+\}/.freeze
         ESCAPED_NON_BACKSLASH = /\\[^\\]/.freeze
 
         def on_dstr(node)

lib/rubocop/cop/util.rb

@@ -108,7 +108,7 @@ def to_string_literal(string)
       end
 
       def trim_string_interporation_escape_character(str)
-        str.gsub(/\\\#{(.*?)\}/) { "\#{#{Regexp.last_match(1)}}" }
+        str.gsub(/\\\#\{(.*?)\}/) { "\#{#{Regexp.last_match(1)}}" }
       end
 
       def interpret_string_escapes(string)

lib/rubocop/target_ruby.rb

@@ -52,7 +52,10 @@ def find_version
         file = ruby_version_file
         return unless file && File.file?(file)
 
+        # rubocop:disable Lint/MixedRegexpCaptureTypes
+        # `(ruby-)` is not a capture type.
         File.read(file).match(/\A(ruby-)?(?<version>\d+\.\d+)/) do |md|
+          # rubocop:enable Lint/MixedRegexpCaptureTypes
           md[:version].to_f
         end
       end

spec/rubocop/cop/lint/mixed_regexp_capture_types_spec.rb

@@ -30,4 +30,46 @@
       /(?<foo>bar)(?:bar)/
     RUBY
   end
+
+  # RuboCop does not know a value of variables that it will contain in the regexp literal.
+  # For example, `/(?<foo>#{var}*)` is interpreted as `/(?<foo>*)`.
+  # So it does not offense when variables are used in regexp literals.
+  context 'when containing a non-regexp literal' do
+    it 'does not register an offence when containing a lvar' do
+      expect_no_offenses(<<~'RUBY')
+        var = '(\d+)'
+        /(?<foo>#{var}*)/
+      RUBY
+    end
+
+    it 'does not register an offence when containing a ivar' do
+      expect_no_offenses(<<~'RUBY')
+        /(?<foo>#{@var}*)/
+      RUBY
+    end
+
+    it 'does not register an offence when containing a cvar' do
+      expect_no_offenses(<<~'RUBY')
+        /(?<foo>#{@@var}*)/
+      RUBY
+    end
+
+    it 'does not register an offence when containing a gvar' do
+      expect_no_offenses(<<~'RUBY')
+        /(?<foo>#{$var}*)/
+      RUBY
+    end
+
+    it 'does not register an offence when containing a method' do
+      expect_no_offenses(<<~'RUBY')
+        /(?<foo>#{do_something}*)/
+      RUBY
+    end
+
+    it 'does not register an offence when containing a constant' do
+      expect_no_offenses(<<~'RUBY')
+        /(?<foo>#{CONST}*)/
+      RUBY
+    end
+  end
 end