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Fix #8319: Survive bad parameters in compareCaptured #8320

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Merged
merged 1 commit into from
Feb 17, 2020
Merged

Fix #8319: Survive bad parameters in compareCaptured #8320

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6 changes: 5 additions & 1 deletion compiler/src/dotty/tools/dotc/core/TypeComparer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1239,7 +1239,11 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] w
if (leftRoot.isStable || (ctx.isAfterTyper || ctx.mode.is(Mode.TypevarsMissContext))
&& leftRoot.member(tparam.name).exists) {
val captured = TypeRef(leftRoot, tparam)
isSubArg(captured, arg2)
try isSubArg(captured, arg2)
catch case ex: TypeError =>
// The captured reference could be illegal and cause a
// TypeError to be thrown in argDenot
false
}
else if (v > 0)
isSubType(paramBounds(tparam).hi, arg2)
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14 changes: 14 additions & 0 deletions tests/pos/i8319.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
package example

sealed abstract class Tree[T]
case class Lam[T,U]() extends Tree[Any]
case class App[T,U]() extends Tree[Any]
case class Var() extends Tree[Any]

object Branch:
def unapply(branch: Lam[?,?] | App[?,?]): true = true

private def foo(s: Option[Tree[?]]) = s match // seems to only occur in a nested pattern
case Some(_: Var) => true // must come first
case Some(Branch()) => true // must be unapply and not direct type check
case _ => false