Allow ** syntax to be used for calling methods that do not accept keywords

Treat the ** syntax as passing a copy of the hash as the last
positional argument.  If the hash being double splatted is empty, do
not add a positional argument.

Remove rb_no_keyword_hash, no longer needed.

hash.c

@@ -30,8 +30,6 @@
 # endif
 #endif
 
-VALUE rb_no_keyword_hash;
-
 #ifndef HASH_DEBUG
 #define HASH_DEBUG 0
 #endif
@@ -3276,8 +3274,6 @@ inspect_hash(VALUE hash, VALUE dummy, int recur)
 static VALUE
 rb_hash_inspect(VALUE hash)
 {
-    if (hash == rb_no_keyword_hash)
-	return rb_usascii_str_new2("{(NO KEYWORD)}");
     if (RHASH_EMPTY_P(hash))
 	return rb_usascii_str_new2("{}");
     return rb_exec_recursive(inspect_hash, hash, 0);
@@ -6277,10 +6273,6 @@ Init_Hash(void)
      */
     rb_define_global_const("ENV", envtbl);
 
-    rb_no_keyword_hash = rb_hash_new();
-    rb_hash_freeze(rb_no_keyword_hash);
-    rb_gc_register_mark_object(rb_no_keyword_hash);
-
     /* for callcc */
     ruby_register_rollback_func_for_ensure(hash_foreach_ensure, hash_foreach_ensure_rollback);
 

internal.h

@@ -2397,7 +2397,6 @@ VALUE rb_str_normalize_ospath(const char *ptr, long len);
 /* hash.c (export) */
 VALUE rb_hash_delete_entry(VALUE hash, VALUE key);
 VALUE rb_ident_hash_new(void);
-extern VALUE rb_no_keyword_hash;
 
 /* io.c (export) */
 void rb_maygvl_fd_fix_cloexec(int fd);

vm.c

@@ -2779,9 +2779,6 @@ static VALUE core_hash_merge_kwd(VALUE hash, VALUE kw);
 static VALUE
 core_hash_merge(VALUE hash, long argc, const VALUE *argv)
 {
-    if (hash == rb_no_keyword_hash) {
-	hash = rb_hash_new();
-    }
     Check_Type(hash, T_HASH);
     VM_ASSERT(argc % 2 == 0);
     rb_hash_bulk_insert(argc, argv, hash);
@@ -2815,8 +2812,6 @@ m_core_hash_merge_kwd(VALUE recv, VALUE hash, VALUE kw)
 static VALUE
 core_hash_merge_kwd(VALUE hash, VALUE kw)
 {
-    if (RHASH_EMPTY_P(hash) && kw == rb_no_keyword_hash)
-	return rb_no_keyword_hash;
     rb_hash_foreach(rb_to_hash_type(kw), kwmerge_i, hash);
     return hash;
 }

vm_args.c

@@ -186,11 +186,6 @@ args_rest_array(struct args_info *args)
 static int
 keyword_hash_p(VALUE *kw_hash_ptr, VALUE *rest_hash_ptr)
 {
-    if (*kw_hash_ptr == rb_no_keyword_hash) {
-	*kw_hash_ptr = Qnil;
-	*rest_hash_ptr = Qfalse;
-	return TRUE;
-    }
     *rest_hash_ptr = rb_check_hash_type(*kw_hash_ptr);
 
     if (!NIL_P(*rest_hash_ptr)) {
@@ -487,7 +482,7 @@ args_setup_kw_parameters(rb_execution_context_t *const ec, const rb_iseq_t *cons
 static inline void
 args_setup_kw_rest_parameter(VALUE keyword_hash, VALUE *locals)
 {
-    locals[0] = NIL_P(keyword_hash) ? rb_no_keyword_hash : rb_hash_dup(keyword_hash);
+    locals[0] = NIL_P(keyword_hash) ? rb_hash_new() : rb_hash_dup(keyword_hash);
 }
 
 static inline void
@@ -513,6 +508,20 @@ fill_keys_values(st_data_t key, st_data_t val, st_data_t ptr)
     return ST_CONTINUE;
 }
 
+static inline int
+ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq) {
+    if (!(iseq->body->param.flags.has_kw) &&
+	      !(iseq->body->param.flags.has_kwrest)) {
+	keyword_hash = rb_check_hash_type(keyword_hash);
+
+	if (!NIL_P(keyword_hash) && RHASH_EMPTY_P(keyword_hash)) {
+	    return 1;
+	}
+    }
+
+    return 0;
+}
+
 static inline VALUE
 get_loc(struct rb_calling_info *calling, const struct rb_call_info *ci)
 {
@@ -533,20 +542,6 @@ rb_warn_last_hash_to_keyword(struct rb_calling_info *calling, const struct rb_ca
     }
 }
 
-static inline void
-rb_warn_keyword_to_last_hash(struct rb_calling_info *calling, const struct rb_call_info *ci)
-{
-    if (calling->recv == Qundef) return;
-    VALUE loc = get_loc(calling, ci);
-    if (NIL_P(loc)) {
-        rb_warn("The keyword argument for `%s' is used as the last parameter", rb_id2name(ci->mid));
-    }
-    else {
-        rb_warn("The keyword argument for `%s' (defined at %s:%d) is used as the last parameter",
-                rb_id2name(ci->mid), RSTRING_PTR(RARRAY_AREF(loc, 0)), FIX2INT(RARRAY_AREF(loc, 1)));
-    }
-}
-
 static int
 setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * const iseq,
 			 struct rb_calling_info *const calling,
@@ -563,7 +558,6 @@ 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 k2n_warned = FALSE;
 
     vm_check_canary(ec, orig_sp);
     /*
@@ -619,21 +613,21 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
 	given_argc += RARRAY_LENINT(args->rest) - 1;
         if (kw_flag & VM_CALL_KW_SPLAT) {
             int len = RARRAY_LENINT(args->rest);
-            if (len > 0 && RARRAY_AREF(args->rest, len - 1) == rb_no_keyword_hash) {
+            if (len > 0 && ignore_keyword_hash_p(RARRAY_AREF(args->rest, len - 1), iseq)) {
                 arg_rest_dup(args);
                 rb_ary_pop(args->rest);
                 given_argc--;
                 kw_flag &= ~VM_CALL_KW_SPLAT;
-            }
+	    }
         }
     }
     else {
         if (kw_flag & VM_CALL_KW_SPLAT) {
-            if (args->argv[args->argc-1] == rb_no_keyword_hash) {
+            if (ignore_keyword_hash_p(args->argv[args->argc-1], iseq)) {
                 args->argc--;
                 given_argc--;
                 kw_flag &= ~VM_CALL_KW_SPLAT;
-            }
+	    }
         }
 	args->rest = Qfalse;
     }
@@ -655,12 +649,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
     /* argc check */
     if (given_argc < min_argc) {
 	if (given_argc == min_argc - 1 && args->kw_argv) {
-	    /* Warn the following:
-	     * def foo(a, k:1) p [a, k] end
-	     * foo(k:42) #=> [{:k=>42}, 1]
-	     */
-            rb_warn_keyword_to_last_hash(calling, ci);
-	    k2n_warned = TRUE;
 	    args_stored_kw_argv_to_hash(args);
 	    given_argc = args_argc(args);
 	}
@@ -702,16 +690,6 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
 	    }
 	}
     }
-    else if (!k2n_warned &&
-	    !((kw_flag & VM_CALL_KWARG) && iseq->body->param.flags.has_kw) &&
-	    given_argc > min_argc &&
-	    (kw_flag & (VM_CALL_KWARG | VM_CALL_KW_SPLAT))) {
-	/* Warn the following:
-	 * def foo(x, opt=1) p [x]; end
-	 * foo(k:42) #=> [{:k=>42}]
-	 */
-        rb_warn_keyword_to_last_hash(calling, ci);
-    }
 
     if (given_argc > max_argc && max_argc != UNLIMITED_ARGUMENTS) {
 	if (arg_setup_type == arg_setup_block) {
@@ -880,8 +858,6 @@ vm_caller_setup_arg_splat(rb_control_frame_t *cfp, struct rb_calling_info *calli
 
         CHECK_VM_STACK_OVERFLOW(cfp, len);
 
-        if (ptr[len - 1] == rb_no_keyword_hash) len--;
-
         for (i = 0; i < len; i++) {
             *cfp->sp++ = ptr[i];
         }
@@ -899,14 +875,6 @@ vm_caller_setup_arg_kw(rb_control_frame_t *cfp, struct rb_calling_info *calling,
     VALUE *sp = cfp->sp;
     int i;
 
-    /* Warn the following:
-     * def foo(x) p [x] end
-     * foo(k:42) #=> [{:k=>42}]
-     */
-    if (!cfunc) {
-        rb_warn_keyword_to_last_hash(calling, ci);
-    }
-
     for (i=0; i<kw_len; i++) {
 	rb_hash_aset(h, passed_keywords[i], (sp - kw_len)[i]);
     }