[SPARK-31975][SQL] Show AnalysisException when WindowFunction is used without WindowExpression

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/CheckAnalysis.scala

@@ -158,6 +158,11 @@ trait CheckAnalysis extends PredicateHelper {
           case g: GroupingID =>
             failAnalysis("grouping_id() can only be used with GroupingSets/Cube/Rollup")
 
+          case e: Expression if e.children.exists(_.isInstanceOf[WindowFunction]) &&
+            !e.isInstanceOf[WindowExpression] =>
+            val w = e.children.find(_.isInstanceOf[WindowFunction]).get
+            failAnalysis(s"Window function $w requires an OVER clause.")
+
           case w @ WindowExpression(AggregateExpression(_, _, true, _, _), _) =>
             failAnalysis(s"Distinct window functions are not supported: $w")
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/AnalysisSuite.scala

@@ -884,4 +884,15 @@ class AnalysisSuite extends AnalysisTest with Matchers {
       Seq("Intersect can only be performed on tables with the compatible column types. " +
         "timestamp <> double at the second column of the second table"))
   }
+
+  test("throw user facing error when use WindowFunction directly") {
+    assertAnalysisError(testRelation2.select(RowNumber()),
+      Seq("Window function row_number() requires an OVER clause."))
+
+    assertAnalysisError(testRelation2.select(Sum(RowNumber())),
+      Seq("Window function row_number() requires an OVER clause."))
+
+    assertAnalysisError(testRelation2.select(RowNumber() + 1),
+      Seq("Window function row_number() requires an OVER clause."))
+  }
 }