patch 8.2.3423: Vim9: list += list creates a new list in :def function Commit: https://github.com/vim/vim/commit/07802044b90b2cbcc64b2dfe235f019d7c37589c Author: Bram Moolenaar <Bram@vim.org> Date: Thu Sep 9 23:01:14 2021 +0200 patch 8.2.3423: Vim9: list += list creates a new list in :def function Problem: Vim9: list += list creates a new list in :def function. Solution: Append to the existing list.

--- a/src/structs.h
+++ b/src/structs.h
@@ -4106,6 +4106,9 @@ typedef enum
     EXPR_MULT,		// *
     EXPR_DIV,		// /
     EXPR_REM,		// %
+    // used with ISN_ADDLIST
+    EXPR_COPY,		// create new list
+    EXPR_APPEND,	// append to first list
 } exprtype_T;
 
 /*