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Try either when compare an intersection against an applied type in GADT mode #15175

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Try either when compare an intersection against an applied type in GADT mode #15175

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9 changes: 9 additions & 0 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 @@ -1198,6 +1198,14 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
case _ => false
} && { GADTused = true; true }

def tryGadtAnd1: Boolean =
ctx.mode.is(Mode.GadtConstraintInference) && {
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Suggested change
ctx.mode.is(Mode.GadtConstraintInference) && {
necessaryConstraintsOnly && {

Perhaps is better?

tp1 match
case AndType(tp11, tp12) =>
either(recur(tp11, tp2), recur(tp12, tp2))
case _ => false
}

tycon2 match {
case param2: TypeParamRef =>
isMatchingApply(tp1) ||
Expand All @@ -1213,6 +1221,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
case info2: ClassInfo =>
tycon2.name.startsWith("Tuple") &&
defn.isTupleNType(tp2) && recur(tp1, tp2.toNestedPairs) ||
tryGadtAnd1 ||
tryBaseType(info2.cls)
case _ =>
fourthTry
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21 changes: 21 additions & 0 deletions tests/neg/i11545.scala
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@@ -0,0 +1,21 @@
// Taken from
// https://github.com/lampepfl/dotty/issues/11545#issuecomment-787609144
class test0 {
type AA
trait S[A]
trait Inv[A]

class P[X] extends S[Inv[X] & AA]

}

@main def test: Unit =
new test0:
type AA = Inv[String]

def patmat[A, Y](s: S[Inv[A] & Y]): A = s match {
case p: P[x] =>
"Hello" // error
}

val got: Int = patmat[Int, AA](new P)