[Bug #19985] Raise LoadError with the converted feature name

`Kernel#require` converts feature name objects that have the `to_path`
method such as `Pathname`, but had used the original object on error
and had resulted in an unexpected `TypeError`.

load.c

@@ -935,6 +935,7 @@ load_unlock(rb_vm_t *vm, const char *ftptr, int done)
     }
 }
 
+static VALUE rb_require_string_internal(VALUE fname);
 
 /*
  *  call-seq:
@@ -997,7 +998,7 @@ rb_f_require_relative(VALUE obj, VALUE fname)
         rb_loaderror("cannot infer basepath");
     }
     base = rb_file_dirname(base);
-    return rb_require_string(rb_file_absolute_path(fname, base));
+    return rb_require_string_internal(rb_file_absolute_path(fname, base));
 }
 
 typedef int (*feature_func)(rb_vm_t *vm, const char *feature, const char *ext, int rb, int expanded, const char **fn);
@@ -1210,7 +1211,6 @@ require_internal(rb_execution_context_t *ec, VALUE fname, int exception, bool wa
     volatile bool reset_ext_config = false;
     struct rb_ext_config prev_ext_config;
 
-    fname = rb_get_path(fname);
     path = rb_str_encode_ospath(fname);
     RUBY_DTRACE_HOOK(REQUIRE_ENTRY, RSTRING_PTR(fname));
     saved_path = path;
@@ -1335,6 +1335,12 @@ ruby_require_internal(const char *fname, unsigned int len)
 
 VALUE
 rb_require_string(VALUE fname)
+{
+    return rb_require_string_internal(FilePathValue(fname));
+}
+
+static VALUE
+rb_require_string_internal(VALUE fname)
 {
     rb_execution_context_t *ec = GET_EC();
     int result = require_internal(ec, fname, 1, RTEST(ruby_verbose));
@@ -1352,7 +1358,9 @@ rb_require_string(VALUE fname)
 VALUE
 rb_require(const char *fname)
 {
-    return rb_require_string(rb_str_new_cstr(fname));
+    struct RString fake;
+    VALUE str = rb_setup_fake_str(&fake, fname, strlen(fname), 0);
+    return rb_require_string_internal(str);
 }
 
 static int

test/ruby/test_require.rb

@@ -6,11 +6,27 @@ require 'tmpdir'
 
 class TestRequire < Test::Unit::TestCase
   def test_load_error_path
-    filename = "should_not_exist"
-    error = assert_raise(LoadError) do
-      require filename
-    end
-    assert_equal filename, error.path
+    Tempfile.create(["should_not_exist", ".rb"]) {|t|
+      filename = t.path
+      t.close
+      File.unlink(filename)
+
+      error = assert_raise(LoadError) do
+        require filename
+      end
+      assert_equal filename, error.path
+
+      # with --disable=gems
+      assert_separately(["-", filename], "#{<<~"begin;"}\n#{<<~'end;'}")
+      begin;
+        filename = ARGV[0]
+        path = Struct.new(:to_path).new(filename)
+        error = assert_raise(LoadError) do
+          require path
+        end
+        assert_equal filename, error.path
+      end;
+    }
   end
 
   def test_require_invalid_shared_object