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Skip bypassing unapply for scala 2 case classes to allow for single-element named tuple in unapply #23603

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Merged
merged 5 commits into from
Jul 30, 2025
Merged

Skip bypassing unapply for scala 2 case classes to allow for single-element named tuple in unapply #23603

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2183e53
Skip bypassing unapply for scala 2 case classes to allow for single-e…
aherlihy Jul 25, 2025
4e684dc
more precise check
aherlihy Jul 25, 2025
7f95284
Make check more precise for single named tuple selector in pattern match
aherlihy Jul 29, 2025
3c5e4a0
minimize diff
aherlihy Jul 29, 2025
73da315
Refactor out getOfGetMatch
aherlihy Jul 30, 2025
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5 changes: 3 additions & 2 deletions compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -343,7 +343,8 @@ object PatternMatcher {
receiver.ensureConforms(defn.NonEmptyTupleTypeRef), // If scrutinee is a named tuple, cast to underlying tuple
Literal(Constant(i)))

if (isSyntheticScala2Unapply(unapp.symbol) && caseAccessors.length == args.length)
val wasNamedArg = args.length == 1 && args.head.removeAttachment(FirstTransform.WasNamedArg).isDefined
if (isSyntheticScala2Unapply(unapp.symbol) && caseAccessors.length == args.length && !wasNamedArg)
def tupleSel(sym: Symbol) =
// If scrutinee is a named tuple, cast to underlying tuple, so that we can
// continue to select with _1, _2, ...
Expand Down Expand Up @@ -388,7 +389,7 @@ object PatternMatcher {
letAbstract(get) { getResult =>
def isUnaryNamedTupleSelectArg(arg: Tree) =
get.tpe.widenDealias.isNamedTupleType
&& arg.removeAttachment(FirstTransform.WasNamedArg).isDefined
&& wasNamedArg
// Special case: Normally, we pull out the argument wholesale if
// there is only one. But if the argument is a named argument for
// a single-element named tuple, we have to select the field instead.
Expand Down
9 changes: 9 additions & 0 deletions tests/run/i23131.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
import scala.NamedTuple
@main
def Test =
Some((name = "Bob")) match {
case Some(name = a) => println(a)
}
// (name = "Bob") match { // works fine
// case (name = a) => println (a)
// }
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