Implement `NoMethodError#args`.

include/mruby/error.h

@@ -19,6 +19,7 @@ void mrb_exc_print(mrb_state *mrb, struct RObject *exc);
 void mrb_print_backtrace(mrb_state *mrb);
 mrb_value mrb_exc_backtrace(mrb_state *mrb, mrb_value exc);
 mrb_value mrb_get_backtrace(mrb_state *mrb);
+mrb_noreturn void mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_int argc, const mrb_value *argv, const char *fmt, ...);
 
 /* declaration for fail method */
 mrb_value mrb_f_raise(mrb_state*, mrb_value);

mrblib/error.rb

@@ -48,6 +48,12 @@ end
 
 # ISO 15.2.32
 class NoMethodError < NameError
+  attr_reader :args
+
+  def initialize(message=nil, name=nil, args=nil)
+    @args = args
+    super message, name
+  end
 end
 
 # ISO 15.2.33

src/class.c

@@ -1216,8 +1216,7 @@ mrb_bob_missing(mrb_state *mrb, mrb_value mod)
     repr = mrb_any_to_s(mrb, mod);
   }
 
-  mrb_raisef(mrb, E_NOMETHOD_ERROR, "undefined method '%S' for %S",
-             mrb_sym2str(mrb, name), repr);
+  mrb_no_method_error(mrb, name, alen, a, "undefined method '%S' for %S", mrb_sym2str(mrb, name), repr);
   /* not reached */
   return mrb_nil_value();
 }

src/error.c

@@ -442,6 +442,20 @@ mrb_sys_fail(mrb_state *mrb, const char *mesg)
   }
 }
 
+mrb_noreturn void
+mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_int argc, const mrb_value *argv, char const* fmt, ...)
+{
+  mrb_value exc;
+  va_list ap;
+
+  va_start(ap, fmt);
+  exc = mrb_funcall(mrb, mrb_obj_value(E_NOMETHOD_ERROR), "new", 3,
+                    mrb_vformat(mrb, fmt, ap), mrb_symbol_value(id),
+                    mrb_ary_new_from_values(mrb, argc, argv));
+  va_end(ap);
+  mrb_exc_raise(mrb, exc);
+}
+
 void
 mrb_init_exception(mrb_state *mrb)
 {

test/t/nomethoderror.rb

@@ -11,3 +11,16 @@ end
 assert('NoMethodError superclass', '15.2.32.2') do
   assert_equal NameError, NoMethodError.superclass
 end
+
+assert('NoMethodError#args', '15.2.32.2.1') do
+  a = NoMethodError.new 'test', :test, [1, 2]
+  assert_equal [1, 2], a.args
+
+  assert_nothing_raised do
+    begin
+      doesNotExistAsAMethodNameForVerySure 3, 1, 4
+    rescue NoMethodError => e
+      assert_equal [3, 1, 4], e.args
+    end
+  end
+end