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Use upper bound of effectively sealed abstract types in exhaustivity checking #23909

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11 changes: 10 additions & 1 deletion compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -708,6 +708,8 @@ object SpaceEngine {
else NoType
}.filter(_.exists)
parts
case tref: TypeRef if tref.symbol.isAbstractOrAliasType && !tref.info.hiBound.isNothingType =>
rec(tref.info.hiBound, mixins)
case _ => ListOfNoType
end rec

Expand Down Expand Up @@ -853,7 +855,14 @@ object SpaceEngine {
}) ||
tpw.isRef(defn.BooleanClass) ||
classSym.isAllOf(JavaEnum) ||
classSym.is(Case)
classSym.is(Case) ||
(tpw.isInstanceOf[TypeRef] && {
val tref = tpw.asInstanceOf[TypeRef]
if (tref.symbol.isAbstractOrAliasType && !tref.info.hiBound.isNothingType)
isCheckable(tref.info.hiBound)
else
false
})

!sel.tpe.hasAnnotation(defn.UncheckedAnnot)
&& !sel.tpe.hasAnnotation(defn.RuntimeCheckedAnnot)
Expand Down
18 changes: 18 additions & 0 deletions tests/pos/i23620.scala
View file Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
trait Foo
trait Bar

type FooOrBar = FooOrBar.Type
object FooOrBar:
opaque type Type <: (Foo | Bar) = Foo | Bar

def bar: FooOrBar = new Bar {}

trait Buz

@main def main =
val p: FooOrBar | Buz = FooOrBar.bar

p match
case _: Foo => println("foo")
case _: Buz => println("buz")
case _: Bar => println("bar")
16 changes: 16 additions & 0 deletions tests/warn/i23620b.check
View file Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
-- [E029] Pattern Match Exhaustivity Warning: tests/warn/i23620b.scala:20:2 --------------------------------------------
20 | p match // warn
| ^
| match may not be exhaustive.
|
| It would fail on pattern case: _: Bar
|
| longer explanation available when compiling with `-explain`
-- [E029] Pattern Match Exhaustivity Warning: tests/warn/i23620b.scala:23:2 --------------------------------------------
23 | p2 match { //warn
| ^^
| match may not be exhaustive.
|
| It would fail on pattern case: _: Bar
|
| longer explanation available when compiling with `-explain`
25 changes: 25 additions & 0 deletions tests/warn/i23620b.scala
View file Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
trait Foo
trait Bar

type FooOrBar = FooOrBar.Type
object FooOrBar:
opaque type Type <: (Foo | Bar) = Foo | Bar

def bar: FooOrBar = new Bar {}

type OnlyFoo = OnlyFoo.Type
object OnlyFoo:
opaque type Type <: (Foo | Bar) = Foo

def foo: OnlyFoo = new Foo {}

@main def main =
val p: FooOrBar= FooOrBar.bar
val p2: OnlyFoo = OnlyFoo.foo

p match // warn
case _: Foo => println("foo")

p2 match { //warn
case _: Foo => println("foo")
}
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