tests squiggly heredoc

* See #175
* See [Feature 9098]

language/fixtures/squiggly_heredoc.rb

@@ -0,0 +1,8 @@
+module StringSpecs
+  def self.squiggly_message
+    <<~HEREDOC
+      character density, n.:
+        The number of very weird people in the office.
+    HEREDOC
+  end
+end

language/string_spec.rb

@@ -2,6 +2,10 @@
 
 require File.expand_path('../../spec_helper', __FILE__)
 
+ruby_version_is "2.3" do
+  require File.expand_path('../fixtures/squiggly_heredoc', __FILE__)
+end
+
 # TODO: rewrite these horrid specs. it "are..." seriously?!
 
 describe "Ruby character strings" do
@@ -176,6 +180,12 @@
     s.should == '    foo bar#{@ip}' + "\n"
   end
 
+  ruby_version_is "2.3" do
+    it "allows HEREDOC with <<~'identifier', allowing to indent identifier and content" do
+      StringSpecs.squiggly_message.should == "character density, n.:\n  The number of very weird people in the office.\n"
+    end
+  end
+
   it "calls #to_s when the object is not a String" do
     obj = mock('to_s')
     obj.stub!(:to_s).and_return('42')