class.c: no fstring singleton class

* class.c (singleton_class_of): prohibit fstrings from creating
  singleton classes.
  temporary measure for [ruby-dev:49867] [Bug #12923]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56747 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 0 deletions

diff --git a/class.c b/class.c
index aed3ee42f2..350e2cc31b 100644
--- a/class.c
+++ b/class.c
@@ -1602,6 +1602,9 @@ singleton_class_of(VALUE obj)
 	switch (BUILTIN_TYPE(obj)) {
 	  case T_FLOAT: case T_BIGNUM: case T_SYMBOL:
 	    goto no_singleton;
+	  case T_STRING:
+	    if (FL_TEST_RAW(obj, RSTRING_FSTR)) goto no_singleton;
+	    break;
 	}
     }