[Haml] Fix the multiline/filter issues.

lib/haml/precompiler.rb

@@ -774,8 +774,12 @@ END
         end
 
       # `flat?' here is a little outdated,
-      # so we have to manually check if the previous line closes the flat block.
-      unless flat? && (@line.text.empty? || @line.tabs >= @template_tabs)
+      # so we have to manually check if either the previous or current line
+      # closes the flat block,
+      # as well as whether a new block is opened
+      @line.tabs if @line
+      unless (flat? && !closes_flat?(line) && !closes_flat?(@line)) ||
+          (@line && @line.text[0] == ?: && line.full =~ %r[^#{@line.full[/^\s+/]}\s])
         if line.text.empty?
           newline
           return next_line
@@ -787,6 +791,10 @@ END
       @next_line = line
     end
 
+    def closes_flat?(line)
+      line && !line.text.empty? && line.full !~ /^#{@flat_spaces}/
+    end
+
     def un_next_line(line)
       @template.unshift line
       @template_index -= 1

test/haml/engine_test.rb

@@ -325,18 +325,6 @@ HTML
 HAML
   end
 
-  def test_multiline_with_colon_after_filter
-    assert_equal(<<HTML, render(<<HAML))
-Foo
-Bar
-HTML
-:plain
-  Foo
-= { :a => "Bar",      |
-    :b => "Baz" }[:a] |
-HAML
-  end
-
   def test_multiline_in_filter
     assert_equal(<<HTML, render(<<HAML))
 Foo |