2 files changed, 55 insertions, 2 deletions
diff --git a/lib/prism/ffi.rb b/lib/prism/ffi.rb
index eda61b3ead..35b91e41b2 100644
--- a/lib/prism/ffi.rb
+++ b/lib/prism/ffi.rb
@@ -478,10 +478,35 @@ module Prism
         values << scopes.length
 
         scopes.each do |scope|
+          locals = nil
+          forwarding = 0
+
+          case scope
+          when Array
+            locals = scope
+          when Scope
+            locals = scope.locals
+
+            scope.forwarding.each do |forward|
+              case forward
+              when :*     then forwarding |= 0x1
+              when :**    then forwarding |= 0x2
+              when :&     then forwarding |= 0x4
+              when :"..." then forwarding |= 0x8
+              else raise ArgumentError, "invalid forwarding value: #{forward}"
+              end
+            end
+          else
+            raise TypeError, "wrong argument type #{scope.class.inspect} (expected Array or Prism::Scope)"
+          end
+
           template << "L"
-          values << scope.length
+          values << locals.length
+
+          template << "C"
+          values << forwarding
 
-          scope.each do |local|
+          locals.each do |local|
             name = local.name
             template << "L"
             values << name.bytesize
diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index e76ea7e17e..9a3e7c5b79 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -879,4 +879,32 @@ module Prism
       freeze
     end
   end
+
+  # This object is passed to the various Prism.* methods that accept the
+  # `scopes` option as an element of the list. It defines both the local
+  # variables visible at that scope as well as the forwarding parameters
+  # available at that scope.
+  class Scope
+    # The list of local variables that are defined in this scope. This should be
+    # defined as an array of symbols.
+    attr_reader :locals
+
+    # The list of local variables that are forwarded to the next scope. This
+    # should by defined as an array of symbols containing the specific values of
+    # :*, :**, :&, or :"...".
+    attr_reader :forwarding
+
+    # Create a new scope object with the given locals and forwarding.
+    def initialize(locals, forwarding)
+      @locals = locals
+      @forwarding = forwarding
+    end
+  end
+
+  # Create a new scope with the given locals and forwarding options that is
+  # suitable for passing into one of the Prism.* methods that accepts the
+  # `scopes` option.
+  def self.scope(locals: [], forwarding: [])
+    Scope.new(locals, forwarding)
+  end
 end