[SPARK-29026][SQL] Improve error message in schemaFor in trait without companion object constructor

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala

@@ -906,7 +906,18 @@ trait ScalaReflection extends Logging {
    * only defines a constructor via `apply` method.
    */
   private def getCompanionConstructor(tpe: Type): Symbol = {
-    tpe.typeSymbol.asClass.companion.asTerm.typeSignature.member(universe.TermName("apply"))
+    def throwUnsupportedOperation = {
+      throw new UnsupportedOperationException(s"Unable to find constructor for $tpe. " +
+        s"This could happen if $tpe is an interface, or a trait without companion object " +
+        "constructor.")
+    }
+    tpe.typeSymbol.asClass.companion match {
+      case NoSymbol => throwUnsupportedOperation
+      case sym => sym.asTerm.typeSignature.member(universe.TermName("apply")) match {
+        case NoSymbol => throwUnsupportedOperation
+        case constructorSym => constructorSym
+      }
+    }
   }
 
   protected def constructParams(tpe: Type): Seq[Symbol] = {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala

@@ -138,6 +138,14 @@ trait ScroogeLikeExample extends Product1[Int] with Serializable {
   override def hashCode: Int = x
 }
 
+/** Counter-examples to [[ScroogeLikeExample]] as a trait without a companion object constructor */
+trait TraitProductWithoutCompanion extends Product1[Int] {}
+
+/** Counter-examples to [[ScroogeLikeExample]] as a trait with no-constructor companion object */
+object TraitProductWithNoConstructorCompanion {}
+
+trait TraitProductWithNoConstructorCompanion extends Product1[Int] {}
+
 class ScalaReflectionSuite extends SparkFunSuite {
   import org.apache.spark.sql.catalyst.ScalaReflection._
 
@@ -404,6 +412,20 @@ class ScalaReflectionSuite extends SparkFunSuite {
         StructField("x", IntegerType, nullable = false))), nullable = true))
   }
 
+  test("SPARK-29026: schemaFor for trait without companion object throws exception ") {
+    val e = intercept[UnsupportedOperationException] {
+      schemaFor[TraitProductWithoutCompanion]
+    }
+    assert(e.getMessage.contains("Unable to find constructor"))
+  }
+
+  test("SPARK-29026: schemaFor for trait with no-constructor companion throws exception ") {
+    val e = intercept[UnsupportedOperationException] {
+      schemaFor[TraitProductWithNoConstructorCompanion]
+    }
+    assert(e.getMessage.contains("Unable to find constructor"))
+  }
+
   test("SPARK-27625: annotated data types") {
     assert(serializerFor[FooWithAnnotation].dataType == StructType(Seq(
       StructField("f1", StringType),