Eliminate arrow pattern, replace with pattern matches

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

@@ -26,33 +26,36 @@ object HiveTypeCoercion {
   // See https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Types.
   // The conversion for integral and floating point types have a linear widening hierarchy:
   private val numericPrecedence =
-    Seq(ByteType, ShortType, IntegerType, LongType, FloatType, DoubleType, DecimalType.Unlimited)
+    IndexedSeq(
+      ByteType,
+      ShortType,
+      IntegerType,
+      LongType,
+      FloatType,
+      DoubleType,
+      DecimalType.Unlimited)
 
   /**
    * Find the tightest common type of two types that might be used in a binary expression.
    * This handles all numeric types except fixed-precision decimals interacting with each other or
    * with primitive types, because in that case the precision and scale of the result depends on
    * the operation. Those rules are implemented in [[HiveTypeCoercion.DecimalPrecision]].
    */
-  def findTightestCommonType(t1: DataType, t2: DataType): Option[DataType] = {
-    val valueTypes = Seq(t1, t2).filter(t => t != NullType)
-    if (valueTypes.distinct.size > 1) {
-      // Promote numeric types to the highest of the two and all numeric types to unlimited decimal
-      if (numericPrecedence.contains(t1) && numericPrecedence.contains(t2)) {
-        Some(numericPrecedence.filter(t => t == t1 || t == t2).last)
-      } else if (t1.isInstanceOf[DecimalType] && t2.isInstanceOf[DecimalType]) {
-        // Fixed-precision decimals can up-cast into unlimited
-        if (t1 == DecimalType.Unlimited || t2 == DecimalType.Unlimited) {
-          Some(DecimalType.Unlimited)
-        } else {
-          None
-        }
-      } else {
-        None
-      }
-    } else {
-      Some(if (valueTypes.size == 0) NullType else valueTypes.head)
-    }
+  val findTightestCommonType: (DataType, DataType) => Option[DataType] = {
+    case (t1, t2) if t1 == t2 => Some(t1)
+    case (NullType, t1) => Some(t1)
+    case (t1, NullType) => Some(t1)
+
+    // Promote numeric types to the highest of the two and all numeric types to unlimited decimal
+    case (t1, t2) if Seq(t1, t2).forall(numericPrecedence.contains) =>
+      val index = numericPrecedence.lastIndexWhere(t => t == t1 || t == t2)
+      Some(numericPrecedence(index))
+
+    // Fixed-precision decimals can up-cast into unlimited
+    case (DecimalType.Unlimited, _: DecimalType) => Some(DecimalType.Unlimited)
+    case (_: DecimalType, DecimalType.Unlimited) => Some(DecimalType.Unlimited)
+
+    case _ => None
   }
 }