Fix parsing of other line continuation scenarios

Author: seven1m

lib/natalie/parser.rb

@@ -785,8 +785,14 @@ def visit_string_concat_node(node)
                     end
           end
           left
+        when %i[str dstr]
+          right[1] = left[1] + right[1]
+          right
+        when %i[dstr str]
+          left << right
+          left
         else
-          debug node
+          raise SyntaxError, "Unexpected nodes for StringConcatNode: #{left.inspect} and #{right.inspect}"
         end
       end
 

test/natalie/string_test.rb

@@ -758,4 +758,19 @@ def initialize(s)
       "a\nb\nc".each_line(chomp: true).to_a.should == %w[a b c]
     end
   end
+
+  describe 'line continuation' do
+    s = 'foo' \
+        'bar'
+    s.should == 'foobar'
+    s = 'foo' \
+        "bar#{1 + 1}"
+    s.should == 'foobar2'
+    s = "foo#{1 + 1}" \
+        "bar#{1 + 1}"
+    s.should == 'foo2bar2'
+    s = "foo#{1 + 1}" \
+        'bar'
+    s.should == 'foo2bar'
+  end
 end