Ensure runtime error's backtrace line number is correct

lib/hamlit/parser.rb

@@ -51,7 +51,7 @@ module Hamlit
         width = next_width
         if width != @current_indent * 2
           if width != Hamlit::EOF && (width > @current_indent * 2 || width.odd?)
-            ast << [:newline]
+            ast << [:multi, [:newline], [:newline]]
             ast << syntax_error(
               "inconsistent indentation: #{2 * @current_indent} spaces used for indentation, "\
               "but the rest of the document was indented using #{width} spaces"

spec/hamlit/engine/error_spec.rb

@@ -22,5 +22,24 @@ describe Hamlit::Engine do
       HAML
         to raise_error(Hamlit::SyntaxError, 'inconsistent indentation: 2 spaces used for indentation, but the rest of the document was indented using 1 spaces')
     end
+
+    it 'raises syntax error which has correct line number in backtrace' do
+      begin
+        render_string(<<-HAML.unindent)
+          %1
+            %2
+            %3
+            %4
+          %5
+            %6
+            %7
+             %8 this is invalid indent
+          %9
+        HAML
+      rescue Hamlit::SyntaxError => e
+        line_number = e.backtrace_locations.first.to_s.match(/:(\d+):/)[1]
+        expect(line_number).to eq('8')
+      end
+    end
   end
 end