* compile.c (compile_dstr_fragments): reduced needless literal.

* parse.y (xstring, regexp, dsym, literal_concat, evstr2dstr):
  literal at the top of dstr is no longer needed if it is empty,
  since concatstrings and toregexp always create new strings.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24212 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_literal.rb

@@ -59,6 +59,10 @@ class TestRubyLiteral < Test::Unit::TestCase
     assert_equal '16', "#{2 ** 4}"
     s = "string"
     assert_equal s, "#{s}"
+    a = 'Foo'
+    b = "#{a}" << 'Bar'
+    assert_equal('Foo', a, 'r3842')
+    assert_equal('FooBar', b, 'r3842')
   end
 
   def test_dsymbol