[Fix rubocop#2647] Allow xstr interpolations

CHANGELOG.md

@@ -11,6 +11,7 @@
 * [#2630](https://github.com/bbatsov/rubocop/issues/2630): Take frozen string literals into account in `Style/MutableConstant`. ([@segiddins][])
 * [#2642](https://github.com/bbatsov/rubocop/issues/2642): Support assignment via `||=` in `Style/MutableConstant`. ([@segiddins][])
 * [#2646](https://github.com/bbatsov/rubocop/issues/2646): Fix auto-correcting assignment to a constant in `Style/ConditionalAssignment`. ([@segiddins][])
+* [#2647](https://github.com/bbatsov/rubocop/issues/2647): Allow `xstr` interpolations in `Lint/LiteralInInterpolation`. ([@segiddins][])
 
 ### Changes
 

lib/rubocop/cop/lint/literal_in_interpolation.rb

@@ -17,6 +17,7 @@ def on_dstr(node)
             final_node = begin_node.children.last
             next unless final_node
             next if special_keyword?(final_node)
+            next if final_node.xstr_type?
             next unless final_node.literal?
 
             add_offense(final_node, :expression)

spec/rubocop/cop/lint/literal_in_interpolation_spec.rb

@@ -11,6 +11,11 @@
     expect(cop.offenses).to be_empty
   end
 
+  it 'accepts interpolation of xstr' do
+    inspect_source(cop, '"this is #{`a`} silly"')
+    expect(cop.offenses).to be_empty
+  end
+
   shared_examples 'literal interpolation' do |literal|
     it "registers an offense for #{literal} in interpolation" do
       inspect_source(cop, %("this is the \#{#{literal}}"))