diff --git a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala index 20b0099d82e2..9fb3c00c67c4 100644 --- a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala +++ b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala @@ -648,21 +648,38 @@ object SpaceEngine { // we get // <== refineUsingParent(NatT, class Succ, []) = Succ[NatT] // <== isSub(Succ[NatT] <:< Succ[Succ[]]) = false - def getAppliedClass(tp: Type): Type = tp match - case tp @ AppliedType(_: HKTypeLambda, _) => tp - case tp @ AppliedType(tycon: TypeRef, _) if tycon.symbol.isClass => tp + def getAppliedClass(tp: Type): (Type, List[Type]) = tp match + case tp @ AppliedType(_: HKTypeLambda, _) => (tp, Nil) + case tp @ AppliedType(tycon: TypeRef, _) if tycon.symbol.isClass => (tp, tp.args) case tp @ AppliedType(tycon: TypeProxy, _) => getAppliedClass(tycon.superType.applyIfParameterized(tp.args)) - case tp => tp - val tp = getAppliedClass(tpOriginal) - def getChildren(sym: Symbol): List[Symbol] = + case tp => (tp, Nil) + val (tp, typeArgs) = getAppliedClass(tpOriginal) + // This function is needed to get the arguments of the types that will be applied to the class. + // This is necessary because if the arguments of the types contain Nothing, + // then this can affect whether the class will be taken into account during the exhaustiveness check + def getTypeArgs(parent: Symbol, child: Symbol, typeArgs: List[Type]): List[Type] = + val superType = child.typeRef.superType + if typeArgs.exists(_.isBottomType) && superType.isInstanceOf[ClassInfo] then + val parentClass = superType.asInstanceOf[ClassInfo].declaredParents.find(_.classSymbol == parent).get + val paramTypeMap = Map.from(parentClass.argTypes.map(_.typeSymbol).zip(typeArgs)) + val substArgs = child.typeRef.typeParamSymbols.map(param => paramTypeMap.getOrElse(param, WildcardType)) + substArgs + else Nil + def getChildren(sym: Symbol, typeArgs: List[Type]): List[Symbol] = sym.children.flatMap { child => if child eq sym then List(sym) // i3145: sealed trait Baz, val x = new Baz {}, Baz.children returns Baz... else if tp.classSymbol == defn.TupleClass || tp.classSymbol == defn.NonEmptyTupleClass then List(child) // TupleN and TupleXXL classes are used for Tuple, but they aren't Tuple's children - else if (child.is(Private) || child.is(Sealed)) && child.isOneOf(AbstractOrTrait) then getChildren(child) - else List(child) + else if (child.is(Private) || child.is(Sealed)) && child.isOneOf(AbstractOrTrait) then + getChildren(child, getTypeArgs(sym, child, typeArgs)) + else + val childSubstTypes = child.typeRef.applyIfParameterized(getTypeArgs(sym, child, typeArgs)) + // if a class contains a field of type Nothing, + // then it can be ignored in pattern matching, because it is impossible to obtain an instance of it + val existFieldWithBottomType = childSubstTypes.fields.exists(_.info.isBottomType) + if existFieldWithBottomType then Nil else List(child) } - val children = trace(i"getChildren($tp)")(getChildren(tp.classSymbol)) + val children = trace(i"getChildren($tp)")(getChildren(tp.classSymbol, typeArgs)) val parts = children.map { sym => val sym1 = if (sym.is(ModuleClass)) sym.sourceModule else sym diff --git a/tests/init-global/pos/i18629.scala b/tests/init-global/pos/i18629.scala index f97c21ee918d..03f1f5d5cda4 100644 --- a/tests/init-global/pos/i18629.scala +++ b/tests/init-global/pos/i18629.scala @@ -1,6 +1,6 @@ object Foo { val bar = List() match { case List() => ??? - case _ => ??? + case null => ??? } } diff --git a/tests/patmat/i13931.scala b/tests/patmat/i13931.scala index 0d8d9eb9dcd3..562f059771c1 100644 --- a/tests/patmat/i13931.scala +++ b/tests/patmat/i13931.scala @@ -3,5 +3,5 @@ class Test: case Seq() => println("empty") case _ => println("non-empty") - def test2 = IndexedSeq() match { case IndexedSeq() => case _ => } + def test2 = IndexedSeq() match { case IndexedSeq() => case null => } def test3 = IndexedSeq() match { case IndexedSeq(1) => case _ => } diff --git a/tests/warn/patmat-nothing-exhaustive.scala b/tests/warn/patmat-nothing-exhaustive.scala new file mode 100644 index 000000000000..4e9181256fda --- /dev/null +++ b/tests/warn/patmat-nothing-exhaustive.scala @@ -0,0 +1,10 @@ +enum TestAdt: + case Inhabited + case Uninhabited(no: Nothing) + +def test1(t: TestAdt): Int = t match + case TestAdt.Inhabited => 1 + +def test2(o: Option[Option[Nothing]]): Int = o match + case Some(None) => 1 + case None => 2