[GR-18163] Don't accept integer as first parameter to String#rindex

PullRequest: truffleruby/3211

Author: bjfish

CHANGELOG.md

@@ -33,6 +33,7 @@ Compatibility:
 * Do not call `IO#flush` dynamically from `IO#close` (#2594, @gogainda).
 * Implement `rb_str_new_static` for C extensions that use it (@aardvark179).
 * Rewrote `ArrayEachIteratorNode` and re-introduced `each` specs for MRI parity when mutating arrays whilst iterating, rather than crashing (#2587, @MattAlp)
+* Update `String#rindex` to only accept `Regexp` or objects convertable to `String` as the first parameter (#2608, @bjfish).
 
 Performance:
 

spec/ruby/core/string/rindex_spec.rb

@@ -4,13 +4,17 @@
 require_relative 'fixtures/utf-8-encoding'
 
 describe "String#rindex with object" do
-  it "raises a TypeError if obj isn't a String, Integer or Regexp" do
+  it "raises a TypeError if obj isn't a String or Regexp" do
     not_supported_on :opal do
       -> { "hello".rindex(:sym) }.should raise_error(TypeError)
     end
     -> { "hello".rindex(mock('x')) }.should raise_error(TypeError)
   end
 
+  it "raises a TypeError if obj is an Integer" do
+    -> { "hello".rindex(42) }.should raise_error(TypeError)
+  end
+
   it "doesn't try to convert obj to an integer via to_int" do
     obj = mock('x')
     obj.should_not_receive(:to_int)

src/main/ruby/truffleruby/core/string.rb

@@ -1087,23 +1087,7 @@ def rindex(sub, finish=undefined)
 
     byte_finish = Primitive.string_byte_index_from_char_index(self, finish)
 
-    case sub
-    when Integer
-      if finish == size
-        return nil if finish == 0
-      end
-
-      begin
-        str = sub.chr
-      rescue RangeError
-        return nil
-      end
-
-      if byte_index = Primitive.find_string_reverse(self, str, byte_finish)
-        return Primitive.string_byte_character_index(self, byte_index)
-      end
-
-    when Regexp
+    if Primitive.object_kind_of?(sub, Regexp)
       Primitive.encoding_ensure_compatible self, sub
 
       match_data = Truffle::RegexpOperations.search_region(sub, self, 0, byte_finish, false, true)