raise error if string arg is given to Kernel#instance_eval

src/kernel.c

@@ -557,12 +557,10 @@ mrb_obj_init_copy(mrb_state *mrb, mrb_value self)
 /* 15.3.1.3.18 */
 /*
  *  call-seq:
- *     obj.instance_eval(string [, filename [, lineno]] )   -> obj
  *     obj.instance_eval {| | block }                       -> obj
  *
- *  Evaluates a string containing Ruby source code, or the given block,
- *  within the context of the receiver (_obj_). In order to set the
- *  context, the variable +self+ is set to _obj_ while
+ *  Evaluates the given block,within  the context of the receiver (_obj_). 
+ *  In order to set the context, the variable +self+ is set to _obj_ while
  *  the code is executing, giving the code access to _obj_'s
  *  instance variables. In the version of <code>instance_eval</code>
  *  that takes a +String+, the optional second and third
@@ -580,9 +578,11 @@ mrb_obj_init_copy(mrb_state *mrb, mrb_value self)
 mrb_value
 mrb_obj_instance_eval(mrb_state *mrb, mrb_value self)
 {
-  mrb_value b;
+  mrb_value a, b;
 
-  mrb_get_args(mrb, "&", &b);
+  if (mrb_get_args(mrb, "|S&", &a, &b) == 1) {
+    mrb_raise(mrb, mrb->eRuntimeError_class, "instance_eval with string not implemented");
+  }
   return mrb_yield_with_self(mrb, b, 0, 0, self);
 }