Add YJIT codegen for objtostring (#5149)

This is the minimal correct objtostring implementation in YJIT.
For correctness, it is important that to_string not get called on strings or subclasses of string.
There is a new test for this behavior.

A follow up should implement an optimized version for other types as performed in `vm_objtostring`.

Co-authored-by: John Hawthorn <jhawthorn@github.com>

Co-authored-by: John Hawthorn <jhawthorn@github.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/bootstraptest/test_yjit.rb b/bootstraptest/test_yjit.rb
index 33e9a35462..f1900f9f3f 100644
--- a/bootstraptest/test_yjit.rb
+++ b/bootstraptest/test_yjit.rb
@@ -1214,6 +1214,23 @@ assert_equal 'foo123', %q{
   make_str("foo", 123)
 }
 
+# test string interpolation with overridden to_s
+assert_equal 'foo', %q{
+  class String
+    def to_s
+      "bad"
+    end
+  end
+
+  def make_str(foo)
+    "#{foo}"
+  end
+
+  make_str("foo")
+  make_str("foo")
+}
+
+
 # test invokebuiltin as used in struct assignment
 assert_equal '123', %q{
   def foo(obj)