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Modify type erasure logic of nullable unions for Scala 2 pseudo-unions #24130

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Modify type erasure logic of nullable unions for Scala 2 pseudo-unions #24130

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16 changes: 10 additions & 6 deletions compiler/src/dotty/tools/dotc/core/TypeErasure.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -681,7 +681,15 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
if e1.isInstanceOf[WildcardType] || e2.isInstanceOf[WildcardType] then WildcardType
else erasedGlb(e1, e2)
case OrType(tp1, tp2) =>
if isSymbol && sourceLanguage.isScala2 && ctx.settings.scalajs.value then
val e1 = this(tp1)
val e2 = this(tp2)
val result = if e1.isInstanceOf[WildcardType] || e2.isInstanceOf[WildcardType]
then WildcardType
else TypeComparer.orType(e1, e2, isErased = true)
def isNullStripped =
tp2.isNullType && e1.derivesFrom(defn.ObjectClass)
|| tp1.isNullType && e2.derivesFrom(defn.ObjectClass)
if isSymbol && sourceLanguage.isScala2 && ctx.settings.scalajs.value && !isNullStripped then
// In Scala2Unpickler we unpickle Scala.js pseudo-unions as if they were
// real unions, but we must still erase them as Scala 2 would to emit
// the correct signatures in SJSIR.
Expand All @@ -692,11 +700,7 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
// impact on overriding relationships so it's best to leave them
// alone (and this doesn't impact the SJSIR we generate).
JSDefinitions.jsdefn.PseudoUnionType
else
val e1 = this(tp1)
val e2 = this(tp2)
if e1.isInstanceOf[WildcardType] || e2.isInstanceOf[WildcardType] then WildcardType
else TypeComparer.orType(e1, e2, isErased = true)
else result
case tp: MethodType =>
def paramErasure(tpToErase: Type) =
erasureFn(sourceLanguage, semiEraseVCs, isConstructor, isSymbol, inSigName = false)(tpToErase)
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