string.c: pool only bare strings in fstring

* string.c (fstr_update_callback): pool bare strings only.
* string.c (rb_fstring): return the original string with sharing a
  fstring if it has extra attributes, not the fstring itself.
  [ruby-dev:49188] [Bug #11386]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51360 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/-ext-/string/test_fstring.rb

@@ -0,0 +1,64 @@
+require 'test/unit'
+require '-test-/string'
+
+class Test_String_Fstring < Test::Unit::TestCase
+  def assert_fstring(str)
+    fstr = Bug::String.fstring(str)
+    yield str
+    yield fstr
+  end
+
+  def test_taint_shared_string
+    str = __method__.to_s.dup
+    str.taint
+    assert_fstring(str) {|s| assert_predicate(s, :tainted?)}
+  end
+
+  def test_taint_normal_string
+    str = __method__.to_s * 3
+    str.taint
+    assert_fstring(str) {|s| assert_predicate(s, :tainted?)}
+  end
+
+  def test_taint_registered_tainted
+    str = __method__.to_s * 3
+    str.taint
+    assert_fstring(str) {|s| assert_predicate(s, :tainted?)}
+
+    str = __method__.to_s * 3
+    assert_fstring(str) {|s| assert_not_predicate(s, :tainted?)}
+  end
+
+  def test_taint_registered_untainted
+    str = __method__.to_s * 3
+    assert_fstring(str) {|s| assert_not_predicate(s, :tainted?)}
+
+    str = __method__.to_s * 3
+    str.taint
+    assert_fstring(str) {|s| assert_predicate(s, :tainted?)}
+  end
+
+  def test_instance_variable
+    str = __method__.to_s * 3
+    str.instance_variable_set(:@test, 42)
+    str.freeze
+    assert_fstring(str) {|s| assert_send([s, :instance_variable_defined?, :@test])}
+  end
+
+  def test_singleton_method
+    str = __method__.to_s * 3
+    def str.foo
+    end
+    str.freeze
+    assert_fstring(str) {|s| assert_send([s, :respond_to?, :foo])}
+  end
+
+  class S < String
+  end
+
+  def test_subclass
+    str = S.new(__method__.to_s * 3)
+    str.freeze
+    assert_fstring(str) {|s| assert_instance_of(S, s)}
+  end
+end