[Haml] Fix an error line-numbering bug with =.

This is a bad solution, as it breaks up merged text unnecessarily.
This breaking up may not be fixable
without some refactoring of the precompiler, though,
so that's being pushed off to the master branch
to be released as part of 2.4.

doc-src/HAML_CHANGELOG.md

@@ -15,6 +15,12 @@
 * Use `ensure` to protect the resetting of the Haml output buffer
   against exceptions that are raised within the compiled Haml code.
 
+* Fix an error line-numbering bug that appeared if an error was thrown
+  within loud script (`=`).
+  This is not the best solution, as it disables a few optimizations,
+  but it shouldn't have too much effect and the optimizations
+  will hopefully be re-enabled in version 2.4.
+
 ## [2.2.10](http://github.com/nex3/haml/commit/2.2.10)
 
 * Fixed a bug where elements with dynamic attributes and no content

lib/haml/precompiler.rb

@@ -1002,6 +1002,7 @@ END
 
     def resolve_newlines
       return unless @newlines > 0
+      flush_merged_text unless @to_merge.all? {|type, *_| type == :text}
       @precompiled << "\n" * @newlines
       @newlines = 0
     end

test/haml/engine_test.rb

@@ -72,6 +72,7 @@ class EngineTest < Test::Unit::TestCase
     "/ foo\n\n  bar" => ["Illegal nesting: nesting within a tag that already has content is illegal.", 3],
     "!!!\n\n  bar" => ["Illegal nesting: nesting within a header command is illegal.", 3],
     "foo\n:ruby\n  1\n  2\n  3\n- raise 'foo'" => ["foo", 6],
+    "= raise 'foo'\nfoo\nbar\nbaz\nbang" => ["foo", 1],
   }
 
   User = Struct.new('User', :id)