Fixed tag operator for top level node

pkg/yqlib/operator_tag.go

@@ -41,7 +41,7 @@ func assignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode
 				tag = rhs.Front().Value.(*CandidateNode).Node.Value
 			}
 		}
-		candidate.Node.Tag = tag
+		UnwrapDoc(candidate.Node).Tag = tag
 	}
 
 	return matchingNodes, nil

pkg/yqlib/operator_tag_test.go

@@ -26,6 +26,14 @@ var tagOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!str)::'!!map'\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		document:   `32`,
+		expression: `. tag= "!!str"`,
+		expected: []string{
+			"D0, P[], (doc)::\"32\"\n",
+		},
+	},
 	{
 		description: "Set custom tag",
 		document:    `{a: str}`,