patch 8.2.2544: Vim9: error for argument when checking for lambda

Problem:    Vim9: error for argument when checking for lambda.
Solution:   Respect the skip flag. (closes #7887)

Author: brammool

src/testdir/test_vim9_expr.vim

@@ -1922,6 +1922,14 @@ def Test_expr7_lambda()
 
   CheckDefSuccess(['var Fx = (a) => [0,', ' 1]'])
   CheckDefFailure(['var Fx = (a) => [0', ' 1]'], 'E696:', 2)
+
+  # no error for existing script variable when checking for lambda
+  lines =<< trim END
+    vim9script
+    var name = 0
+    eval (name + 2) / 3
+  END
+  CheckScriptSuccess(lines)
 enddef
 
 def NewLambdaWithComments(): func

src/userfunc.c

@@ -82,7 +82,8 @@ one_function_arg(
     }
 
     // Vim9 script: cannot use script var name for argument.
-    if (argtypes != NULL && script_var_exists(arg, p - arg, FALSE, NULL) == OK)
+    if (!skip && argtypes != NULL && script_var_exists(arg, p - arg,
+							    FALSE, NULL) == OK)
     {
 	semsg(_(e_variable_already_declared_in_script), arg);
 	return arg;

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2544,
 /**/
     2543,
 /**/