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Fix redundancy (unreachability) warning #16179

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merged 1 commit into from
Oct 21, 2022
Merged

Fix redundancy (unreachability) warning #16179

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3 changes: 1 addition & 2 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 @@ -534,16 +534,15 @@ class SpaceEngine(using Context) extends SpaceLogic {
val mt: MethodType = unapp.widen match {
case mt: MethodType => mt
case pt: PolyType =>
inContext(ctx.fresh.setExploreTyperState()) {
val tvars = pt.paramInfos.map(newTypeVar(_))
val mt = pt.instantiate(tvars).asInstanceOf[MethodType]
scrutineeTp <:< mt.paramInfos(0)
// force type inference to infer a narrower type: could be singleton
// see tests/patmat/i4227.scala
mt.paramInfos(0) <:< scrutineeTp
instantiateSelected(mt, tvars)
isFullyDefined(mt, ForceDegree.all)
mt
}
}

// Case unapply:
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12 changes: 12 additions & 0 deletions tests/pos/i16123.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
// scalac: -Werror
sealed trait Nat
case class Zero() extends Nat
case class Succ[N <: Nat](n: N) extends Nat

class Test:
def foo(n: Nat): Int = n match
case Zero() => 0
case Succ(Zero()) => 1
case _ => 2 // was: warning for this line

def test = foo(Succ(Succ(Zero()))) // evaluates to 2