diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala index a9b5a39c2a62..9e1767513b21 100644 --- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala +++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala @@ -3518,20 +3518,75 @@ class MatchReducer(initctx: Context) extends TypeComparer(initctx) { false case MatchTypeCasePattern.TypeMemberExtractor(typeMemberName, capture) => + /** Try to remove references to `skolem` from a type in accordance with the spec. + * + * If any reference to `skolem` remains in the result type, + * `refersToSkolem` is set to true. + */ + class DropSkolemMap(skolem: SkolemType) extends TypeMap: + var refersToSkolem = false + def apply(tp: Type): Type = + tp match + case `skolem` => + refersToSkolem = true + tp + case tp: NamedType => + var savedRefersToSkolem = refersToSkolem + refersToSkolem = false + try + val pre1 = apply(tp.prefix) + if refersToSkolem then + tp match + case tp: TermRef => tp.info.widenExpr.dealias match + case info: SingletonType => + refersToSkolem = false + apply(info) + case _ => + tp.derivedSelect(pre1) + case tp: TypeRef => tp.info match + case info: AliasingBounds => + refersToSkolem = false + apply(info.alias) + case _ => + tp.derivedSelect(pre1) + else + tp.derivedSelect(pre1) + finally + refersToSkolem |= savedRefersToSkolem + case tp: LazyRef => + // By default, TypeMap maps LazyRefs lazily. We need to + // force it for `refersToSkolem` to be correctly set. + apply(tp.ref) + case _ => + mapOver(tp) + end DropSkolemMap + /** Try to remove references to `skolem` from `u` in accordance with the spec. + * + * If any reference to `skolem` remains in the result type, return + * NoType instead. + */ + def dropSkolem(u: Type, skolem: SkolemType): Type = + val dmap = DropSkolemMap(skolem) + val res = dmap(u) + if dmap.refersToSkolem then NoType else res + val stableScrut: SingletonType = scrut match case scrut: SingletonType => scrut case _ => SkolemType(scrut) + stableScrut.member(typeMemberName) match case denot: SingleDenotation if denot.exists => val info = denot.info match case alias: AliasingBounds => alias.alias // Extract the alias case ClassInfo(prefix, cls, _, _, _) => prefix.select(cls) // Re-select the class from the prefix case info => info // Notably, RealTypeBounds, which will eventually give a MatchResult.NoInstances - val infoRefersToSkolem = stableScrut.isInstanceOf[SkolemType] && stableScrut.occursIn(info) - val info1 = info match - case info: TypeBounds => info // Will already trigger a MatchResult.NoInstances - case _ if infoRefersToSkolem => RealTypeBounds(info, info) // Explicitly trigger a MatchResult.NoInstances - case _ => info // We have a match + val info1 = stableScrut match + case skolem: SkolemType => + dropSkolem(info, skolem).orElse: + info match + case info: TypeBounds => info // Will already trigger a MatchResult.NoInstances + case _ => RealTypeBounds(info, info) // Explicitly trigger a MatchResult.NoInstances + case _ => info rec(capture, info1, variance = 0, scrutIsWidenedAbstract) case _ => false diff --git a/tests/neg/mt-deskolemize.scala b/tests/neg/mt-deskolemize.scala index 0a58d5db7bc4..505e47637ac4 100644 --- a/tests/neg/mt-deskolemize.scala +++ b/tests/neg/mt-deskolemize.scala @@ -14,3 +14,45 @@ class SimpleLoop2 extends Expr: object Test1: val x: ExtractValue[SimpleLoop1] = 1 // error + +trait Description: + type Elem <: Tuple + +class PrimBroken extends Expr: + type Value = Alias + type Alias = Value // error + +class Prim extends Expr: + type Value = BigInt + +class VecExpr[E <: Expr] extends Expr: + type Value = Vector[ExtractValue[E]] + +trait ProdExpr extends Expr: + val description: Description + type Value = Tuple.Map[description.Elem, [X] =>> ExtractValue[X & Expr]] + + +class MyExpr1 extends ProdExpr: + final val description = new Description: + type Elem = (VecExpr[Prim], MyExpr2) + +class MyExpr2 extends ProdExpr: + final val description = new Description: + type Elem = (VecExpr[VecExpr[MyExpr1]], Prim) + +trait Constable[E <: Expr]: + def lit(v: ExtractValue[E]): E +object Constable: + given [E <: Expr]: Constable[E] = ??? + +object Test2: + def fromLiteral[E <: Expr : Constable](v: ExtractValue[E]): E = + summon[Constable[E]].lit(v) + val x0: ExtractValue[Prim] = "" // error + val x1: ExtractValue[PrimBroken] = 1 // error + + val foo: MyExpr2 = new MyExpr2 + val v: foo.Value = (Vector(Vector()), 1) // error: Recursion limit exceeded + val c: MyExpr2 = fromLiteral: + (Vector(Vector()), 1) // error: Recursion limit exceeded diff --git a/tests/pos/mt-deskolemize.scala b/tests/pos/mt-deskolemize.scala new file mode 100644 index 000000000000..34f38289b24d --- /dev/null +++ b/tests/pos/mt-deskolemize.scala @@ -0,0 +1,55 @@ +trait Expr: + type Value + +object Expr: + type Of[V] = Expr { type Value = V } + type ExtractValue[F <: Expr] = F match + case Expr.Of[v] => v +import Expr.ExtractValue + +class Prim extends Expr: + type Value = Alias + type Alias = BigInt + +class VecExpr[E <: Expr] extends Expr: + type Value = Vector[ExtractValue[E]] + +trait Description: + type Elem <: Tuple + +trait ProdExpr extends Expr: + val description: Description + type Value = Tuple.Map[description.Elem, [X] =>> ExtractValue[X & Expr]] + +class MyExpr1 extends ProdExpr: + final val description = new Description: + type Elem = (VecExpr[Prim], Prim) + +class MyExpr2 extends ProdExpr: + final val description = new Description: + type Elem = (VecExpr[VecExpr[MyExpr1]], Prim) + +trait ProdExprAlt[T <: Tuple] extends Expr: + type Value = Tuple.Map[T, [X] =>> ExtractValue[X & Expr]] + +class MyExpr3 extends ProdExprAlt[(Prim, VecExpr[Prim], Prim)] + +trait Constable[E <: Expr]: + def lit(v: ExtractValue[E]): E +object Constable: + given [E <: Expr]: Constable[E] = ??? + +object Test: + def fromLiteral[E <: Expr : Constable](v: ExtractValue[E]): E = + summon[Constable[E]].lit(v) + val a: Prim = fromLiteral(1) + val b: VecExpr[Prim] = fromLiteral(Vector(1)) + val c: MyExpr1 = fromLiteral((Vector(1), 1)) + val d: MyExpr2 = fromLiteral(Vector(Vector((Vector(1), 1))), 2) + val e: MyExpr3 = fromLiteral((1, Vector(1), 1)) + val f: ProdExprAlt[(MyExpr1, VecExpr[MyExpr3])] = fromLiteral: + ( + (Vector(1), 1), + Vector((1, Vector(1), 1), (2, Vector(1), 2)) + ) + val g: Expr { type Alias = Int; type Value = Alias } = fromLiteral(1)