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WojciechMazurWojciechMazur
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Backport "Fix derivesFrom false negative in provablyDisjointClasses" to 3.7.4 (#23990)
Backports #23834 to the 3.7.4. PR submitted by the release tooling. [skip ci]
2 parents c2d14cf + 13d0a61 commit 532315e

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-8
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7 files changed

+73
-8
lines changed

‎compiler/src/dotty/tools/backend/jvm/CodeGen.scala‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -85,8 +85,8 @@ class CodeGen(val int: DottyBackendInterface, val primitives: DottyPrimitives)(
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case ex: InterruptedException => throw ex
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case ex: CompilationUnit.SuspendException => throw ex
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case ex: Throwable =>
88-
ex.printStackTrace()
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report.error(s"Error while emitting ${unit.source}\n${ex.getMessage}", NoSourcePosition)
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if !ex.isInstanceOf[TypeError] then ex.printStackTrace()
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report.error(s"Error while emitting ${unit.source}\n${ex.getMessage}", cd.sourcePos)
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9191

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def genTastyAndSetAttributes(claszSymbol: Symbol, store: ClassNode): Unit =

‎compiler/src/dotty/tools/dotc/core/SymDenotations.scala‎

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -865,9 +865,23 @@ object SymDenotations {
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* and is the denoting symbol also different from `Null` or `Nothing`?
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* @note erroneous classes are assumed to derive from all other classes
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* and all classes derive from them.
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* @note may return a false negative when `this.info.isInstanceOf[TempClassInfo]`.
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*/
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def derivesFrom(base: Symbol)(using Context): Boolean = false
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/** Could `this` derive from `base` now or in the future.
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* For concistency with derivesFrom, the info is only forced when this is a ClassDenotation.
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* If the info is a TempClassInfo then the baseClassSet may be temporarily approximated as empty.
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* This is problematic when stability of `!derivesFrom(base)` is assumed for soundness,
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* e.g., in `TypeComparer#provablyDisjointClasses`.
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* @note may return a false positive when `this.info.isInstanceOf[TempClassInfo]`.
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*/
879+
final def mayDeriveFrom(base: Symbol)(using Context): Boolean =
880+
this.isInstanceOf[ClassDenotation] && (info.isInstanceOf[TempClassInfo] || derivesFrom(base))
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final def derivesFrom(base: Symbol, defaultIfUnknown: Boolean)(using Context): Boolean =
883+
if defaultIfUnknown/*== true*/ then mayDeriveFrom(base) else derivesFrom(base)
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871885
/** Is this a Scala or Java annotation ? */
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def isAnnotation(using Context): Boolean =
873887
isClass && (derivesFrom(defn.AnnotationClass) || is(JavaAnnotation))

‎compiler/src/dotty/tools/dotc/core/TypeComparer.scala‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -3131,9 +3131,9 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
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* unique value derives from the class.
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*/
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case (tp1: SingletonType, tp2) =>
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!tp1.derivesFrom(tp2.classSymbol)
3134+
!tp1.derivesFrom(tp2.classSymbol, defaultIfUnknown = true)
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case (tp1, tp2: SingletonType) =>
3136-
!tp2.derivesFrom(tp1.classSymbol)
3136+
!tp2.derivesFrom(tp1.classSymbol, defaultIfUnknown = true)
31373137

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/* Now both sides are possibly-parameterized class types `p.C[Ts]` and `q.D[Us]`.
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*
@@ -3189,7 +3189,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
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val cls2BaseClassSet = SymDenotations.BaseClassSet(cls2.classDenot.baseClasses)
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val commonBaseClasses = cls1.classDenot.baseClasses.filter(cls2BaseClassSet.contains(_))
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def isAncestorOfOtherBaseClass(cls: ClassSymbol): Boolean =
3192-
commonBaseClasses.exists(other => (other ne cls) && other.derivesFrom(cls))
3192+
commonBaseClasses.exists(other => (other ne cls) && other.mayDeriveFrom(cls))
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val result = commonBaseClasses.exists { baseClass =>
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!isAncestorOfOtherBaseClass(baseClass) && isBaseTypeWithDisjointArguments(baseClass, innerPending)
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}
@@ -3230,7 +3230,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
32303230
.filter(child => child.exists && child != cls)
32313231

32323232
def eitherDerivesFromOther(cls1: Symbol, cls2: Symbol): Boolean =
3233-
cls1.derivesFrom(cls2) || cls2.derivesFrom(cls1)
3233+
cls1.mayDeriveFrom(cls2) || cls2.mayDeriveFrom(cls1)
32343234

32353235
def smallestNonTraitBase(cls: Symbol): Symbol =
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val classes = if cls.isClass then cls.asClass.baseClasses else cls.info.classSymbols

‎compiler/src/dotty/tools/dotc/core/Types.scala‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -270,15 +270,15 @@ object Types extends TypeUtils {
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/** True if this type is an instance of the given `cls` or an instance of
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* a non-bottom subclass of `cls`.
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*/
273-
final def derivesFrom(cls: Symbol)(using Context): Boolean = {
273+
final def derivesFrom(cls: Symbol, defaultIfUnknown: Boolean = false)(using Context): Boolean = {
274274
def isLowerBottomType(tp: Type) =
275275
tp.isBottomType
276276
&& (tp.hasClassSymbol(defn.NothingClass)
277277
|| cls != defn.NothingClass && !cls.isValueClass)
278278
def loop(tp: Type): Boolean = try tp match
279279
case tp: TypeRef =>
280280
val sym = tp.symbol
281-
if (sym.isClass) sym.derivesFrom(cls) else loop(tp.superType)
281+
if (sym.isClass) sym.derivesFrom(cls, defaultIfUnknown) else loop(tp.superType)
282282
case tp: AppliedType =>
283283
tp.superType.derivesFrom(cls)
284284
case tp: MatchType =>

‎tests/neg/i17132.min.check‎

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
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-- Error: tests/neg/i17132.min.scala:4:7 -------------------------------------------------------------------------------
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4 |class Q[T <: P[Any]] extends P[R[T]] // error
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4+
| Recursion limit exceeded.
5+
| Maybe there is an illegal cyclic reference?
6+
| If that's not the case, you could also try to increase the stacksize using the -Xss JVM option.
7+
| For the unprocessed stack trace, compile with -Xno-enrich-error-messages.
8+
| A recurring operation is (inner to outer):
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|
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| ...
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|
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
28+
| reduce type t match ...
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| reduce type t match ...
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| reduce type t match ...
31+
| reduce type T match ...

‎tests/neg/i17132.min.scala‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,9 @@
1+
2+
class P[T]
3+
//class Q[T] extends P[R[T]] // ok
4+
class Q[T <: P[Any]] extends P[R[T]] // error
5+
//type Q[T <: P[Any]] <: P[R[T]] // ok
6+
7+
type R[U] = U match
8+
case Q[t] => R[t]
9+
case P[t] => t

‎tests/neg/i17132.scala‎

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
1+
2+
sealed trait Transformation[T]
3+
4+
case object Count extends Transformation[Int]
5+
case class MultiTransformation[T1 <: Transformation[?], T2 <: Transformation[?]](t1: T1, t2: T2) // error cyclic
6+
extends Transformation[MultiTransformationResult[T1, T2]]
7+
8+
type MultiTransformationResult[T1 <: Transformation[?], T2 <: Transformation[?]] <: Tuple = (T1, T2) match {
9+
case (Transformation[t], MultiTransformation[t1, t2]) => t *: MultiTransformationResult[t1, t2]
10+
case (Transformation[t1], Transformation[t2]) => (t1, t2)
11+
}

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