From 58325daae3beefda13ed100782cd19a89cc68771 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Sat, 24 Oct 2020 11:52:30 -0700
Subject: Make String methods return String instances when called on a subclass
 instance

This modifies the following String methods to return String instances
instead of subclass instances:

* String#*
* String#capitalize
* String#center
* String#chomp
* String#chop
* String#delete
* String#delete_prefix
* String#delete_suffix
* String#downcase
* String#dump
* String#each/#each_line
* String#gsub
* String#ljust
* String#lstrip
* String#partition
* String#reverse
* String#rjust
* String#rpartition
* String#rstrip
* String#scrub
* String#slice!
* String#slice/#[]
* String#split
* String#squeeze
* String#strip
* String#sub
* String#succ/#next
* String#swapcase
* String#tr
* String#tr_s
* String#upcase

This also fixes a bug in String#swapcase where it would return the
receiver instead of a copy of the receiver if the receiver was the
empty string.

Some string methods were left to return subclass instances:

* String#+@
* String#-@

Both of these methods will return the receiver (subclass instance)
in some cases, so it is best to keep the returned class consistent.

Fixes [#10845]
---
 spec/ruby/core/string/tr_spec.rb | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

(limited to 'spec/ruby/core/string/tr_spec.rb')

diff --git a/spec/ruby/core/string/tr_spec.rb b/spec/ruby/core/string/tr_spec.rb
index 212d06f679..06be1e6641 100644
--- a/spec/ruby/core/string/tr_spec.rb
+++ b/spec/ruby/core/string/tr_spec.rb
@@ -57,8 +57,16 @@ describe "String#tr" do
     "bla".tr(from_str, to_str).should == "BlA"
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("hello").tr("e", "a").should be_an_instance_of(StringSpecs::MyString)
+  ruby_version_is ''...'3.0' do
+    it "returns subclass instances when called on a subclass" do
+      StringSpecs::MyString.new("hello").tr("e", "a").should be_an_instance_of(StringSpecs::MyString)
+    end
+  end
+
+  ruby_version_is '3.0' do
+    it "returns Stringinstances when called on a subclass" do
+      StringSpecs::MyString.new("hello").tr("e", "a").should be_an_instance_of(String)
+    end
   end
 
   ruby_version_is ''...'2.7' do
-- 
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