From: Yegappan Lakshmanan <yegappan@yahoo.com>
Date: Sat, 31 Jan 2026 10:07:02 +0000 (+0000)
Subject: patch 9.1.2121: Vim9: type issue when modifying a variable using :legacy
X-Git-Tag: v9.1.2121^0
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;ds=sidebyside;p=thirdparty%2Fvim.git

patch 9.1.2121: Vim9: type issue when modifying a variable using :legacy

Problem:  Vim9: type issue when modifying a variable using :legacy
          (kennypete)
Solution: In a vim9 script, when modifying a variable using the legacy
          command, check the type (Yegappan Lakshmanan).

fixes:  #18531
closes: #19292

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/eval.c b/src/eval.c
index 9678ea7f67..d2f06fd114 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1860,7 +1860,6 @@ get_lval_subscript(
     int		flags,	    // GLV_ values
     class_T	*cl_exec)
 {
-    int		vim9script = in_vim9script();
     int		quiet = flags & GLV_QUIET;
     char_u	*key = NULL;
     int		len;
@@ -1908,7 +1907,7 @@ get_lval_subscript(
 		vartype_name(v_type));
 #endif
 
-	if (vim9script && lp->ll_valtype == NULL
+	if (current_script_is_vim9() && lp->ll_valtype == NULL
 		&& v != NULL
 		&& lp->ll_tv == &v->di_tv
 		&& ht != NULL && ht == get_script_local_ht())
@@ -2468,7 +2467,10 @@ set_var_lval(
 	if (lp->ll_valtype != NULL
 		    && check_typval_arg_type(lp->ll_valtype, rettv,
 							      NULL, 0) == FAIL)
+	{
+	    lp->ll_name_end = NULL;
 	    return;
+	}
 
 	// If the lval is a List and the type of the list is not yet set,
 	// then set the item type from the declared type of the variable.
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index a8c6c01cb3..b915b666d5 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -2563,6 +2563,52 @@ def Test_var_type_check()
     defcompile
   END
   v9.CheckScriptSuccess(lines)
+
+  # Modifying a variable type using the legacy command at script level
+  lines =<< trim END
+    vim9script
+    var l: list<number> = [1, 2]
+    legacy let s:l[0] = 'x'
+  END
+  v9.CheckSourceFailure(lines, 'E1012: Type mismatch; expected number but got string', 3)
+
+  # try with dict type
+  lines =<< trim END
+    vim9script
+    var d: dict<number>
+    legacy let s:d['a'] = 'x'
+  END
+  v9.CheckSourceFailure(lines, 'E1012: Type mismatch; expected number but got string', 3)
+
+  # Modifying a variable type using the legacy command in a def function
+  lines =<< trim END
+    vim9script
+    var l: list<number> = [1, 2]
+    def Fn()
+      legacy let s:l[0] = 'x'
+    enddef
+    Fn()
+  END
+  v9.CheckSourceFailure(lines, 'E1012: Type mismatch; expected number but got string', 1)
+
+  # try with dict type
+  lines =<< trim END
+    vim9script
+    var d: dict<string>
+    def Fn()
+      legacy let s:d['a'] = 10
+    enddef
+    Fn()
+  END
+  v9.CheckSourceFailure(lines, 'E1012: Type mismatch; expected string but got number', 1)
+
+  # after the first error, the assignment should be aborted
+  lines =<< trim END
+    vim9script
+    var l: list<number> = [1, 2]
+    legacy let [s:l[0], s:l[1]] = ['x', 1.0]
+  END
+  v9.CheckSourceFailureList(lines, ['', 'E1012: Type mismatch; expected number but got string'], 3)
 enddef
 
 let g:dict_number = #{one: 1, two: 2}
diff --git a/src/version.c b/src/version.c
index 94b463ebe0..8279563519 100644
--- a/src/version.c
+++ b/src/version.c
@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2121,
 /**/
     2120,
 /**/