minimize diff

[Cherry-picked 3c5e4a0]

Author: aherlihy

compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -345,10 +345,10 @@ object PatternMatcher {
 
         // Disable Scala2Unapply optimization if the argument is a named argument for a single-element named tuple to
         // enable selecting the field. See i23131.scala for test cases.
-        val wasSingleNamedArgForNamedTuple =
+        val wasUnaryNamedTupleSelectArgForNamedTuple =
           args.length == 1 && args.head.removeAttachment(FirstTransform.WasNamedArg).isDefined &&
             isGetMatch(unappType) && unapp.select(nme.get, _.info.isParameterless).tpe.widenDealias.isNamedTupleType
-        if (isSyntheticScala2Unapply(unapp.symbol) && caseAccessors.length == args.length && !wasSingleNamedArgForNamedTuple)
+        if (isSyntheticScala2Unapply(unapp.symbol) && caseAccessors.length == args.length && !wasUnaryNamedTupleSelectArgForNamedTuple)
           def tupleSel(sym: Symbol) =
             // If scrutinee is a named tuple, cast to underlying tuple, so that we can
             // continue to select with _1, _2, ...
@@ -397,10 +397,11 @@ object PatternMatcher {
                     // NamedArg trees are eliminated in FirstTransform but for named arguments
                     // of patterns we add a WasNamedArg attachment, which is used to guide the
                     // logic here. See i22900.scala for test cases.
-                    val selectors = if args.length == 1 && !wasSingleNamedArgForNamedTuple then
-                      ref(getResult) :: Nil
-                    else
-                      productSelectors(getResult.info).map(ref(getResult).select(_))
+                    val selectors = args match
+                      case arg :: Nil if !wasUnaryNamedTupleSelectArgForNamedTuple =>
+                        ref(getResult) :: Nil
+                      case _ =>
+                        productSelectors(getResult.info).map(ref(getResult).select(_))
                     matchArgsPlan(selectors, args, onSuccess)
                   }
               }

tests/run/i23131.scala

@@ -3,7 +3,4 @@ import scala.NamedTuple
 def Test =
   Some((name = "Bob")) match {
     case Some(name = a) => println(a)
-  }
-//  (name = "Bob") match { // works fine
-//    case (name = a) => println (a)
-//  }
+  }