Remove empty keyword splats when calling even when using ruby2_keywords

Keeping empty keyword splats for ruby2_keywords methods was
necessary in 2.7 to prevent the final positional hash being
treated as keywords.  Now that keyword argument separation
has been committed, the final positional hash is never
treated as keywords, so there is no need to keep empty
keyword splats when using ruby2_keywords.

test/ruby/test_keyword.rb

@@ -2339,10 +2339,10 @@ class TestKeywordArguments < Test::Unit::TestCase
     assert_equal([[1, h1, 1], {}], o.foo_bar_mod(1, **h1))
     assert_equal([1, h1, 1], o.foo_baz_mod(1, **h1))
 
-    assert_equal([[h1, {}, 1], {}], o.foo_mod(:bar, h1, **{}))
-    assert_equal([h1, {}, 1], o.foo_mod(:baz, h1, **{}))
-    assert_equal([[h1, {}, 1], {}], o.foo_bar_mod(h1, **{}))
-    assert_equal([h1, {}, 1], o.foo_baz_mod(h1, **{}))
+    assert_equal([[h1, 1], {}], o.foo_mod(:bar, h1, **{}))
+    assert_equal([h1, 1], o.foo_mod(:baz, h1, **{}))
+    assert_equal([[h1, 1], {}], o.foo_bar_mod(h1, **{}))
+    assert_equal([h1, 1], o.foo_baz_mod(h1, **{}))
 
     assert_equal([[1, h1, 1], {}], o.foo_mod(:bar, 1, h1))
     assert_equal([1, h1, 1], o.foo_mod(:baz, 1, h1))

test/test_pp.rb

@@ -178,7 +178,7 @@ class PPSingleLineTest < Test::Unit::TestCase
   end
 
   def test_hash_in_array
-    assert_equal("[{}]", PP.singleline_pp([->(*a){a.last}.ruby2_keywords.call(**{})], ''.dup))
+    assert_equal("[{}]", PP.singleline_pp([->(*a){a.last.clear}.ruby2_keywords.call(a: 1)], ''.dup))
     assert_equal("[{}]", PP.singleline_pp([Hash.ruby2_keywords_hash({})], ''.dup))
   end
 end

vm_args.c

@@ -452,7 +452,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
     VALUE keyword_hash = Qnil;
     VALUE * const orig_sp = ec->cfp->sp;
     unsigned int i;
-    int remove_empty_keyword_hash = 1;
     VALUE flag_keyword_hash = 0;
 
     vm_check_canary(ec, orig_sp);
@@ -503,10 +502,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
 	args->kw_argv = NULL;
     }
 
-    if (kw_flag && iseq->body->param.flags.ruby2_keywords) {
-        remove_empty_keyword_hash = 0;
-    }
-
     if (ci->flag & VM_CALL_ARGS_SPLAT) {
         VALUE rest_last = 0;
         int len;
@@ -521,9 +516,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
                 (((struct RHash *)rest_last)->basic.flags & RHASH_PASS_AS_KEYWORDS)) {
                 rest_last = rb_hash_dup(rest_last);
                 kw_flag |= VM_CALL_KW_SPLAT;
-                if (iseq->body->param.flags.ruby2_keywords) {
-                    remove_empty_keyword_hash = 0;
-                }
             }
             else {
                 rest_last = 0;
@@ -532,17 +524,12 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
 
         if (kw_flag & VM_CALL_KW_SPLAT) {
             if (len > 0 && ignore_keyword_hash_p(rest_last, iseq)) {
-                if (remove_empty_keyword_hash) {
-                    arg_rest_dup(args);
-                    rb_ary_pop(args->rest);
-                    given_argc--;
-                    kw_flag &= ~VM_CALL_KW_SPLAT;
-                }
-                else {
-                    flag_keyword_hash = rest_last;
-                }
+                arg_rest_dup(args);
+                rb_ary_pop(args->rest);
+                given_argc--;
+                kw_flag &= ~VM_CALL_KW_SPLAT;
 	    }
-            else if (!remove_empty_keyword_hash && rest_last) {
+            else if (iseq->body->param.flags.ruby2_keywords && rest_last) {
                 flag_keyword_hash = rest_last;
             }
             else if (iseq->body->param.flags.has_kw || iseq->body->param.flags.has_kwrest) {
@@ -557,16 +544,11 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
         if (kw_flag & VM_CALL_KW_SPLAT) {
             VALUE last_arg = args->argv[args->argc-1];
             if (ignore_keyword_hash_p(last_arg, iseq)) {
-                if (remove_empty_keyword_hash) {
-                    args->argc--;
-                    given_argc--;
-                    kw_flag &= ~VM_CALL_KW_SPLAT;
-                }
-                else {
-                    flag_keyword_hash = last_arg;
-                }
+                args->argc--;
+                given_argc--;
+                kw_flag &= ~VM_CALL_KW_SPLAT;
 	    }
-            else if (!remove_empty_keyword_hash) {
+            else if (iseq->body->param.flags.ruby2_keywords) {
                 flag_keyword_hash = last_arg;
             }
             else if (iseq->body->param.flags.has_kw || iseq->body->param.flags.has_kwrest) {