vm_eval.c: fstring instance_eval

* vm_eval.c (singleton_class_for_eval): enable fstring singleton
  class for instance_eval.  [ruby-core:78116] [Bug #12930]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56777 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 10 insertions, 0 deletions

diff --git a/test/ruby/test_eval.rb b/test/ruby/test_eval.rb
index dba54773cb..fc08d61ef5 100644
--- a/test/ruby/test_eval.rb
+++ b/test/ruby/test_eval.rb
@@ -503,6 +503,14 @@ class TestEval < Test::Unit::TestCase
     assert_same a, b
   end
 
+  def test_fstring_instance_eval
+    bug = "[ruby-core:78116] [Bug #12930]".freeze
+    assert_same bug, (bug.instance_eval {self})
+    assert_raise(RuntimeError) {
+      bug.instance_eval {@ivar = true}
+    }
+  end
+
   def test_gced_binding_block
     assert_normal_exit %q{
       def m
diff --git a/vm_eval.c b/vm_eval.c
index ea398e04d2..f0274e1b9a 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -1669,6 +1669,8 @@ singleton_class_for_eval(VALUE self)
     switch (BUILTIN_TYPE(self)) {
       case T_FLOAT: case T_BIGNUM: case T_SYMBOL:
 	return Qnil;
+      case T_STRING:
+	if (FL_TEST_RAW(self, RSTRING_FSTR)) return Qnil;
       default:
 	return rb_singleton_class(self);
     }