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Fix parameter untupling for named tuples (#23440) #24152

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Merged
merged 1 commit into from
Oct 14, 2025
+27 −12
Merged

Fix parameter untupling for named tuples (#23440) #24152

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22 changes: 12 additions & 10 deletions compiler/src/dotty/tools/dotc/typer/Applications.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -153,16 +153,18 @@ object Applications {

def tupleComponentTypes(tp: Type)(using Context): List[Type] =
tp.widenExpr.dealias.normalized match
case tp: AppliedType =>
if defn.isTupleClass(tp.tycon.typeSymbol) then
tp.args
else if tp.tycon.derivesFrom(defn.PairClass) then
val List(head, tail) = tp.args
head :: tupleComponentTypes(tail)
else
case defn.NamedTuple(_, vals) =>
tupleComponentTypes(vals)
case tp: AppliedType =>
if defn.isTupleClass(tp.tycon.typeSymbol) then
tp.args
else if tp.tycon.derivesFrom(defn.PairClass) then
val List(head, tail) = tp.args
head :: tupleComponentTypes(tail)
else
Nil
case _ =>
Nil
case _ =>
Nil

def productArity(tp: Type, errorPos: SrcPos = NoSourcePosition)(using Context): Int =
if (defn.isProductSubType(tp)) productSelectorTypes(tp, errorPos).size else -1
Expand Down Expand Up @@ -2585,7 +2587,7 @@ trait Applications extends Compatibility {
/** Is `formal` a product type which is elementwise compatible with `params`? */
def ptIsCorrectProduct(formal: Type, params: List[untpd.ValDef])(using Context): Boolean =
isFullyDefined(formal, ForceDegree.flipBottom)
&& defn.isProductSubType(formal)
&& (defn.isProductSubType(formal) || formal.isNamedTupleType)
&& tupleComponentTypes(formal).corresponds(params): (argType, param) =>
param.tpt.isEmpty || argType.widenExpr <:< typedAheadType(param.tpt).tpe

Expand Down
5 changes: 3 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Expand Up @@ -1943,8 +1943,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
val firstFormal = protoFormals.head.loBound
if ptIsCorrectProduct(firstFormal, params) then
val isGenericTuple =
firstFormal.derivesFrom(defn.TupleClass)
&& !defn.isTupleClass(firstFormal.typeSymbol)
firstFormal.isNamedTupleType
|| (firstFormal.derivesFrom(defn.TupleClass)
&& !defn.isTupleClass(firstFormal.typeSymbol))
desugared = desugar.makeTupledFunction(params, fnBody, isGenericTuple)
else if protoFormals.length > 1 && params.length == 1 then
def isParamRef(scrut: untpd.Tree): Boolean = scrut match
Expand Down
12 changes: 12 additions & 0 deletions tests/run/i23440.scala
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@@ -0,0 +1,12 @@
@main def Test: Unit =
List((42, "asdads")) match
case List((a, b)) => 1
List((a = 42, b = "asdads")) match
case List((a, b)) => 1
val tuple_list = List((42, "asdads"))
tuple_list.map((a, b) => println(s"$a $b"))
val named_tuple_list = List((a = 42, b = "asdads"))
named_tuple_list.foreach((a, b) => println(s"$a $b"))
named_tuple_list.foreach { case (a, b) => println(s"$a $b") }
val l = Seq.empty[(name: String, age: Int)]
l.map((name, i) => name + i)
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