merge revision(s) 6bcc4664bdaebbf9b28a762ae63f476a1ec6cfb2,bb40c5cbe977de9f36a2a739e94e9b2fd4496b6e,c060bdc2b4ab8eeef5374f4174f5de48ab936d74: [Backport #17541]

	Return new NODE_LIT

	As NODE_ZLIST/NODE_LIST are not markable, cannot be reused as
	NODE_LIT.
	---
	 parse.y | 7 ++-----
	 1 file changed, 2 insertions(+), 5 deletions(-)

	Ensure symbol list node is either NODE_STR or NODE_DSTR

	---
	 parse.y | 11 ++++++++---
	 1 file changed, 8 insertions(+), 3 deletions(-)

	NODE markability should not change by nd_set_type

	---
	 node.c | 31 +++++++++++++++++++++++++------
	 node.h | 12 ++++++++++++
	 2 files changed, 37 insertions(+), 6 deletions(-)

4 files changed, 48 insertions, 15 deletions

diff --git a/node.c b/node.c
index 9b4255bf4a..bef9d7bcbd 100644
--- a/node.c
+++ b/node.c
@@ -1139,7 +1139,7 @@ void
 rb_node_init(NODE *n, enum node_type type, VALUE a0, VALUE a1, VALUE a2)
 {
     n->flags = T_NODE;
-    nd_set_type(n, type);
+    nd_init_type(n, type);
     n->u1.value = a0;
     n->u2.value = a1;
     n->u3.value = a2;
@@ -1238,10 +1238,10 @@ ast_newnode_in_bucket(node_buffer_list_t *nb)
     return &nb->head->buf[nb->idx++];
 }
 
-NODE *
-rb_ast_newnode(rb_ast_t *ast, enum node_type type)
+RBIMPL_ATTR_PURE()
+static bool
+nodetype_markable_p(enum node_type type)
 {
-    node_buffer_t *nb = ast->node_buffer;
     switch (type) {
       case NODE_MATCH:
       case NODE_LIT:
@@ -1254,9 +1254,28 @@ rb_ast_newnode(rb_ast_t *ast, enum node_type type)
       case NODE_ARGS:
       case NODE_ARYPTN:
       case NODE_FNDPTN:
-        return ast_newnode_in_bucket(&nb->markable);
+        return true;
       default:
-        return ast_newnode_in_bucket(&nb->unmarkable);
+        return false;
+    }
+}
+
+NODE *
+rb_ast_newnode(rb_ast_t *ast, enum node_type type)
+{
+    node_buffer_t *nb = ast->node_buffer;
+    node_buffer_list_t *bucket =
+        (nodetype_markable_p(type) ? &nb->markable : &nb->unmarkable);
+    return ast_newnode_in_bucket(bucket);
+}
+
+void
+rb_ast_node_type_change(NODE *n, enum node_type type)
+{
+    enum node_type old_type = nd_type(n);
+    if (nodetype_markable_p(old_type) != nodetype_markable_p(type)) {
+        rb_bug("node type changed: %s -> %s",
+               ruby_node_name(old_type), ruby_node_name(type));
     }
 }
 
diff --git a/node.h b/node.h
index d9dfaa5c2d..192e121fd7 100644
--- a/node.h
+++ b/node.h
@@ -187,6 +187,8 @@ typedef struct RNode {
 
 #define nd_type(n) ((int) (((n)->flags & NODE_TYPEMASK)>>NODE_TYPESHIFT))
 #define nd_set_type(n,t) \
+    rb_node_set_type(n, t)
+#define nd_init_type(n,t) \
     (n)->flags=(((n)->flags&~NODE_TYPEMASK)|((((unsigned long)(t))<<NODE_TYPESHIFT)&NODE_TYPEMASK))
 
 #define NODE_LSHIFT (NODE_TYPESHIFT+7)
@@ -471,9 +473,19 @@ void *rb_parser_realloc(struct parser_params *, void *, size_t);
 void *rb_parser_calloc(struct parser_params *, size_t, size_t);
 void rb_parser_free(struct parser_params *, void *);
 PRINTF_ARGS(void rb_parser_printf(struct parser_params *parser, const char *fmt, ...), 2, 3);
+void rb_ast_node_type_change(NODE *n, enum node_type type);
 
 RUBY_SYMBOL_EXPORT_END
 
+static inline VALUE
+rb_node_set_type(NODE *n, enum node_type t)
+{
+#if RUBY_DEBUG
+    rb_ast_node_type_change(n, t);
+#endif
+    return nd_init_type(n, t);
+}
+
 #if defined(__cplusplus)
 #if 0
 { /* satisfy cc-mode */
diff --git a/parse.y b/parse.y
index 2c63268b0b..70c4ddfcdc 100644
--- a/parse.y
+++ b/parse.y
@@ -10352,12 +10352,17 @@ new_defined(struct parser_params *p, NODE *expr, const YYLTYPE *loc)
 static NODE*
 symbol_append(struct parser_params *p, NODE *symbols, NODE *symbol)
 {
-    if (nd_type(symbol) == NODE_DSTR) {
+    enum node_type type = nd_type(symbol);
+    switch (type) {
+      case NODE_DSTR:
 	nd_set_type(symbol, NODE_DSYM);
-    }
-    else {
+	break;
+      case NODE_STR:
 	nd_set_type(symbol, NODE_LIT);
 	RB_OBJ_WRITTEN(p->ast, Qnil, symbol->nd_lit = rb_str_intern(symbol->nd_lit));
+	break;
+      default:
+	compile_error(p, "unexpected node as symbol: %s", ruby_node_name(type));
     }
     return list_append(p, symbols, symbol);
 }
@@ -11133,9 +11138,7 @@ shareable_literal_constant(struct parser_params *p, enum shareability shareable,
       case NODE_ZLIST:
 	lit = rb_ary_new();
 	OBJ_FREEZE_RAW(lit);
-	nd_set_type(value, NODE_LIT);
-	RB_OBJ_WRITE(p->ast, &value->nd_lit, lit);
-	return value;
+	return NEW_LIT(lit, loc);
 
       case NODE_LIST:
 	lit = rb_ary_new();
@@ -11220,8 +11223,7 @@ shareable_literal_constant(struct parser_params *p, enum shareability shareable,
 	value = make_shareable_node(p, value, false, loc);
     }
     else {
-	nd_set_type(value, NODE_LIT);
-	RB_OBJ_WRITE(p->ast, &value->nd_lit, rb_ractor_make_shareable(lit));
+	value = NEW_LIT(rb_ractor_make_shareable(lit), loc);
     }
 
     return value;
diff --git a/version.h b/version.h
index ced3fdb62e..d106a98cf3 100644
--- a/version.h
+++ b/version.h
@@ -12,7 +12,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 0
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 18
+#define RUBY_PATCHLEVEL 19
 
 #define RUBY_RELEASE_YEAR 2021
 #define RUBY_RELEASE_MONTH 2