Better handle splat in MRHS

Author: kddnewton

lib/prism/translation/ripper.rb

@@ -2812,13 +2812,14 @@ def visit_write_value(node)
           length = elements.length
 
           bounds(elements.first.location)
-          elements.each_with_index.inject(on_args_new) do |args, (element, index)|
+          elements.each_with_index.inject((elements.first.is_a?(SplatNode) && length == 1) ? on_mrhs_new : on_args_new) do |args, (element, index)|
             arg = visit(element)
             bounds(element.location)
 
             if index == length - 1
               if element.is_a?(SplatNode)
-                on_mrhs_add_star(on_mrhs_new_from_args(args), arg)
+                mrhs = index == 0 ? args : on_mrhs_new_from_args(args)
+                on_mrhs_add_star(mrhs, arg)
               else
                 on_mrhs_add(on_mrhs_new_from_args(args), arg)
               end

test/prism/ripper_test.rb

@@ -88,15 +88,12 @@ class RipperTest < TestCase
       unparser/corpus/literal/while.txt
       unparser/corpus/semantic/dstr.txt
       unparser/corpus/semantic/while.txt
-      variables.txt
-      whitequark/asgn_mrhs.txt
       whitequark/bug_480.txt
       whitequark/dedenting_heredoc.txt
       whitequark/dedenting_interpolating_heredoc_fake_line_continuation.txt
       whitequark/dedenting_non_interpolating_heredoc_line_continuation.txt
       whitequark/empty_stmt.txt
       whitequark/if_elsif.txt
-      whitequark/masgn_splat.txt
       whitequark/parser_bug_640.txt
       whitequark/parser_drops_truncated_parts_of_squiggly_heredoc.txt
       whitequark/parser_slash_slash_n_escaping_in_literals.txt