5 files changed, 9 insertions, 24 deletions
diff --git a/mrbgems/mruby-io/src/file.c b/mrbgems/mruby-io/src/file.c
index e65741061..c00663481 100644
--- a/mrbgems/mruby-io/src/file.c
+++ b/mrbgems/mruby-io/src/file.c
@@ -115,7 +115,7 @@ mrb_file_s_unlink(mrb_state *mrb, mrb_value obj)
   mrb_get_args(mrb, "*", &argv, &argc);
   for (i = 0; i < argc; i++) {
     const char *utf8_path;
-    pathv = mrb_convert_type(mrb, argv[i], MRB_TT_STRING, "String", "to_str");
+    pathv = mrb_ensure_string_type(mrb, argv[i]);
     utf8_path = mrb_string_value_cstr(mrb, &pathv);
     path = mrb_locale_from_utf8(utf8_path, -1);
     if (UNLINK(path) < 0) {
diff --git a/mrbgems/mruby-kernel-ext/src/kernel.c b/mrbgems/mruby-kernel-ext/src/kernel.c
index a60e9a210..bc2656399 100644
--- a/mrbgems/mruby-kernel-ext/src/kernel.c
+++ b/mrbgems/mruby-kernel-ext/src/kernel.c
@@ -141,8 +141,7 @@ mrb_f_float(mrb_state *mrb, mrb_value self)
  *     String(arg)   -> string
  *
  *  Returns <i>arg</i> as an <code>String</code>.
- *
- *  First tries to call its <code>to_str</code> method, then its to_s method.
+ *  converted using <code>to_s</code> method.
  *
  *     String(self)        #=> "main"
  *     String(self.class)  #=> "Object"
@@ -154,10 +153,7 @@ mrb_f_string(mrb_state *mrb, mrb_value self)
   mrb_value arg, tmp;
 
   mrb_get_args(mrb, "o", &arg);
-  tmp = mrb_check_convert_type(mrb, arg, MRB_TT_STRING, "String", "to_str");
-  if (mrb_nil_p(tmp)) {
-    tmp = mrb_check_convert_type(mrb, arg, MRB_TT_STRING, "String", "to_s");
-  }
+  tmp = mrb_convert_type(mrb, arg, MRB_TT_STRING, "String", "to_s");
   return tmp;
 }
 
diff --git a/mrbgems/mruby-string-ext/mrblib/string.rb b/mrbgems/mruby-string-ext/mrblib/string.rb
index 27ca30610..9212d83a5 100644
--- a/mrbgems/mruby-string-ext/mrblib/string.rb
+++ b/mrbgems/mruby-string-ext/mrblib/string.rb
@@ -12,8 +12,8 @@ class String
   #     String.try_convert(/re/)      #=> nil
   #
   def self.try_convert(obj)
-    if obj.respond_to?(:to_str)
-      obj.to_str
+    if self === obj
+      obj
     else
       nil
     end
@@ -142,7 +142,7 @@ class String
   #    "abcdef".casecmp("ABCDEF")    #=> 0
   #
   def casecmp(str)
-    self.downcase <=> str.to_str.downcase
+    self.downcase <=> str.__to_str.downcase
   rescue NoMethodError
     nil
   end
diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index 6d661c352..ba7e3c610 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -163,7 +163,7 @@ mrb_str_concat_m(mrb_state *mrb, mrb_value self)
   if (mrb_fixnum_p(str))
     str = mrb_fixnum_chr(mrb, str);
   else
-    str = mrb_string_type(mrb, str);
+    str = mrb_ensure_string_type(mrb, str);
   mrb_str_concat(mrb, self, str);
   return self;
 }
@@ -191,7 +191,7 @@ mrb_str_start_with(mrb_state *mrb, mrb_value self)
   for (i = 0; i < argc; i++) {
     size_t len_l, len_r;
     int ai = mrb_gc_arena_save(mrb);
-    sub = mrb_string_type(mrb, argv[i]);
+    sub = mrb_ensure_string_type(mrb, argv[i]);
     mrb_gc_arena_restore(mrb, ai);
     len_l = RSTRING_LEN(self);
     len_r = RSTRING_LEN(sub);
@@ -220,7 +220,7 @@ mrb_str_end_with(mrb_state *mrb, mrb_value self)
   for (i = 0; i < argc; i++) {
     size_t len_l, len_r;
     int ai = mrb_gc_arena_save(mrb);
-    sub = mrb_string_type(mrb, argv[i]);
+    sub = mrb_ensure_string_type(mrb, argv[i]);
     mrb_gc_arena_restore(mrb, ai);
     len_l = RSTRING_LEN(self);
     len_r = RSTRING_LEN(sub);
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index 781506949..4ccdfd6c3 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -114,12 +114,6 @@ assert('String#concat') do
   assert_equal "Hello World!", "Hello " << "World" << 33
   assert_equal "Hello World!", "Hello ".concat("World").concat(33)
 
-  o = Object.new
-  def o.to_str
-    "to_str"
-  end
-  assert_equal "hi to_str", "hi " << o
-
   assert_raise(TypeError) { "".concat(Object.new) }
 end
 
@@ -128,11 +122,6 @@ assert('String#casecmp') do
   assert_equal 0, "aBcDeF".casecmp("abcdef")
   assert_equal(-1, "abcdef".casecmp("abcdefg"))
   assert_equal 0, "abcdef".casecmp("ABCDEF")
-  o = Object.new
-  def o.to_str
-    "ABCDEF"
-  end
-  assert_equal 0, "abcdef".casecmp(o)
 end
 
 assert('String#count') do