1 files changed, 14 insertions, 0 deletions
diff --git a/lib/prism/polyfill/string.rb b/lib/prism/polyfill/string.rb
new file mode 100644
index 0000000000..3fa9b5a0c5
--- /dev/null
+++ b/lib/prism/polyfill/string.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Polyfill for String#unpack1 with the offset parameter. Not all Ruby engines
+# have Method#parameters implemented, so we check the arity instead if
+# necessary.
+if (unpack1 = String.instance_method(:unpack1)).respond_to?(:parameters) ? unpack1.parameters.none? { |_, name| name == :offset } : (unpack1.arity == 1)
+  String.prepend(
+    Module.new {
+      def unpack1(format, offset: 0) # :nodoc:
+        offset == 0 ? super(format) : self[offset..].unpack1(format) # steep:ignore
+      end
+    }
+  )
+end