Use the `shape_id` rather than `FL_EXIVAR`

We still keep setting `FL_EXIVAR` so that `rb_shape_verify_consistency`
can detect discrepancies.

1 files changed, 1 insertions, 0 deletions

diff --git a/string.c b/string.c
index 6ab768c244..049e824437 100644
--- a/string.c
+++ b/string.c
@@ -486,6 +486,7 @@ build_fstring(VALUE str, struct fstr_update_arg *arg)
     RUBY_ASSERT(OBJ_FROZEN(str));
     RUBY_ASSERT(!FL_TEST_RAW(str, STR_FAKESTR));
     RUBY_ASSERT(!FL_TEST_RAW(str, FL_EXIVAR));
+    RUBY_ASSERT(!rb_obj_exivar_p(str));
     RUBY_ASSERT(RBASIC_CLASS(str) == rb_cString);
     RUBY_ASSERT(!rb_objspace_garbage_object_p(str));