merge revision(s) c6706f15af123bdbb3b39a21903d85c78462d047: [Backport #18241]

	Fix documentation for String#{<<,concat,prepend}

	These methods mutate and return the receiver, they don't create
	and return a new string.

	Fixes [Bug #18241]
	---
	 string.c | 19 ++++++++++---------
	 1 file changed, 10 insertions(+), 9 deletions(-)

2 files changed, 11 insertions, 10 deletions

diff --git a/string.c b/string.c
index 1db7acc8c8..1777125b2b 100644
--- a/string.c
+++ b/string.c
@@ -3155,13 +3155,13 @@ rb_str_concat_literals(size_t num, const VALUE *strary)
 
 /*
  *  call-seq:
- *     string.concat(*objects) -> new_string
+ *     string.concat(*objects) -> string
  *
- *  Returns a new \String containing the concatenation
- *  of +self+ and all objects in +objects+:
+ *  Concatenates each object in +objects+ to +self+ and returns +self+:
  *
  *    s = 'foo'
  *    s.concat('bar', 'baz') # => "foobarbaz"
+ *    s                      # => "foobarbaz"
  *
  *  For each given object +object+ that is an \Integer,
  *  the value is considered a codepoint and converted to a character before concatenation:
@@ -3193,12 +3193,13 @@ rb_str_concat_multi(int argc, VALUE *argv, VALUE str)
 
 /*
  *  call-seq:
- *    string << object -> str
+ *    string << object -> string
+ *
+ *  Concatenates +object+ to +self+ and returns +self+:
  *
- *  Returns a new \String containing the concatenation
- *  of +self+ and +object+:
  *    s = 'foo'
  *    s << 'bar' # => "foobar"
+ *    s          # => "foobar"
  *
  *  If +object+ is an \Integer,
  *  the value is considered a codepoint and converted to a character before concatenation:
@@ -3273,12 +3274,12 @@ rb_str_concat(VALUE str1, VALUE str2)
 
 /*
  *  call-seq:
- *    string.prepend(*other_strings)  -> str
+ *    string.prepend(*other_strings)  -> string
  *
- *  Returns a new \String containing the concatenation
- *  of all given +other_strings+ and +self+:
+ *  Prepends each string in +other_strings+ to +self+ and returns +self+:
  *    s = 'foo'
  *    s.prepend('bar', 'baz') # => "barbazfoo"
+ *    s                       # => "barbazfoo"
  *
  *  Related: String#concat.
  */
diff --git a/version.h b/version.h
index 6903a7c682..e3c26230f6 100644
--- a/version.h
+++ b/version.h
@@ -12,7 +12,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 4
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 161
+#define RUBY_PATCHLEVEL 162
 
 #define RUBY_RELEASE_YEAR 2021
 #define RUBY_RELEASE_MONTH 12