[cpp] add missing `keyword_remap` for closure variables (closes #5029)

src/generators/gencpp.ml

@@ -2878,7 +2878,7 @@ let gen_cpp_ast_expression_tree ctx class_name func_name function_args injection
 
           Hashtbl.iter (fun name value ->
              out !separator; separator := ",";
-             out name
+             out (keyword_remap name)
          )  closure.close_undeclared;
          out "))";
 

tests/unit/src/unit/issues/Issue5029.hx

@@ -0,0 +1,10 @@
+package unit.issues;
+
+class Issue5029 extends Test {
+	function test() {
+		var template = "";
+		var f = function() template = "some";
+		f();
+		eq("some", template);
+	}
+}