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Avoid inf recursion in provablyDisjointClasses #22489

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Merged
merged 3 commits into from
Feb 3, 2025
Merged

Avoid inf recursion in provablyDisjointClasses #22489

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3cd94b4
Avoid inf recursion in provablyDisjointClasses
dwijnand Jan 31, 2025
04f6fc3
Avoid early widening enum val symbols in provablyDisjointClasses
dwijnand Jan 31, 2025
4cd2a97
Document enum value changes in provablyDisjointClasses
dwijnand Feb 3, 2025
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20 changes: 15 additions & 5 deletions compiler/src/dotty/tools/dotc/core/TypeComparer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -3201,14 +3201,15 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
result
end existsCommonBaseTypeWithDisjointArguments

provablyDisjointClasses(cls1, cls2)
provablyDisjointClasses(cls1, cls2, seen = null)
|| existsCommonBaseTypeWithDisjointArguments
end match
}

private def provablyDisjointClasses(cls1: Symbol, cls2: Symbol)(using Context): Boolean =
private def provablyDisjointClasses(cls1: Symbol, cls2: Symbol, seen: util.HashSet[Symbol] | Null)(using Context): Boolean =
def isDecomposable(cls: Symbol): Boolean =
cls.is(Sealed) && !cls.hasAnonymousChild
if seen != null && seen.contains(cls) then false
else cls.is(Sealed) && !cls.hasAnonymousChild

def decompose(cls: Symbol): List[Symbol] =
cls.children.flatMap { child =>
Expand All @@ -3217,6 +3218,13 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
else child :: Nil
}.filter(child => child.exists && child != cls)

inline def seeing(inline cls: Symbol)(inline thunk: util.HashSet[Symbol] => Boolean) =
val seen1 = if seen == null then new util.HashSet[Symbol] else seen
try
seen1 += cls
thunk(seen1)
finally seen1 -= cls

def eitherDerivesFromOther(cls1: Symbol, cls2: Symbol): Boolean =
cls1.derivesFrom(cls2) || cls2.derivesFrom(cls1)

Expand All @@ -3239,9 +3247,11 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
// instantiations of `cls1` (terms of the form `new cls1`) are not
// of type `tp2`. Therefore, we can safely decompose `cls1` using
// `.children`, even if `cls1` is non abstract.
decompose(cls1).forall(x => provablyDisjointClasses(x, cls2))
seeing(cls1): seen1 =>
decompose(cls1).forall(x => provablyDisjointClasses(x, cls2, seen1))
else if (isDecomposable(cls2))
decompose(cls2).forall(x => provablyDisjointClasses(cls1, x))
seeing(cls2): seen1 =>
decompose(cls2).forall(x => provablyDisjointClasses(cls1, x, seen1))
else
false
end provablyDisjointClasses
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22 changes: 22 additions & 0 deletions tests/pos/i22266.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
sealed trait NonPolygon
sealed trait Polygon

sealed trait SymmetryAspect
sealed trait RotationalSymmetry extends SymmetryAspect
sealed trait MaybeRotationalSymmetry extends SymmetryAspect

enum Shape:
case Circle extends Shape with NonPolygon with RotationalSymmetry
case Triangle extends Shape with Polygon with MaybeRotationalSymmetry
case Square extends Shape with Polygon with RotationalSymmetry

object Shape:

def hasPolygon(
rotationalSyms: Vector[Shape & RotationalSymmetry],
maybeSyms: Vector[Shape & MaybeRotationalSymmetry]
): Boolean =
val all = rotationalSyms.concat(maybeSyms)
all.exists:
case _: Polygon => true
case _ => false
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