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Fix #12485: Avoid cycles in testing feasibility of exhaustivity check #12488

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Merged
merged 1 commit into from
May 17, 2021
Merged

Fix #12485: Avoid cycles in testing feasibility of exhaustivity check #12488

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32 changes: 18 additions & 14 deletions compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -793,23 +793,27 @@ class SpaceEngine(using Context) extends SpaceLogic {
private def exhaustivityCheckable(sel: Tree): Boolean = {
// Possible to check everything, but be compatible with scalac by default
def isCheckable(tp: Type): Boolean =
!tp.hasAnnotation(defn.UncheckedAnnot) && {
val tpw = tp.widen.dealias
val tpw = tp.widen.dealias
val classSym = tpw.classSymbol
classSym.is(Sealed) ||
tpw.isInstanceOf[OrType] ||
(tpw.isInstanceOf[AndType] && {
val and = tpw.asInstanceOf[AndType]
isCheckable(and.tp1) || isCheckable(and.tp2)
}) ||
tpw.isRef(defn.BooleanClass) ||
classSym.isAllOf(JavaEnumTrait)

val res = !sel.tpe.hasAnnotation(defn.UncheckedAnnot) && {
ctx.settings.YcheckAllPatmat.value
|| isCheckable(sel.tpe)
|| {
val tpw = sel.tpe.widen.dealias
val classSym = tpw.classSymbol
ctx.settings.YcheckAllPatmat.value ||
classSym.is(Sealed) ||
tpw.isInstanceOf[OrType] ||
(tpw.isInstanceOf[AndType] && {
val and = tpw.asInstanceOf[AndType]
isCheckable(and.tp1) || isCheckable(and.tp2)
}) ||
tpw.isRef(defn.BooleanClass) ||
classSym.isAllOf(JavaEnumTrait) ||
(defn.isProductSubType(tpw) && classSym.is(Case)
&& productSelectorTypes(tpw, sel.srcPos).exists(isCheckable(_)))
classSym.is(Case) && productSelectorTypes(tpw, sel.srcPos).exists(isCheckable(_))
}
}

val res = isCheckable(sel.tpe)
debug.println(s"exhaustivity checkable: ${sel.show} = $res")
res
}
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4 changes: 4 additions & 0 deletions tests/patmat/i12485.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
case class A(a: A)

def foo(x: A) = x match
case A(a) =>