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Emit exhaustivity warning despite uninhabited types
An abstract sealed class with no subtypes is uninhabited (ignoring null for 1 second). Previously the pattern matcher added an eq axiom of "False" in this case, which wipes out the whole formula as the axioms are AND-ed together and with the rest of the pure prop formula. Keeping the definitions of enumerateSubtypes and domain/domainSyms as they are, I believe it's correct to fix this locally to removeVarEq. The branch is dead (indeed it gets a reachability warning) but that shouldn't preclude the emission of exhaustivity warnings. One additional consideration is modelNull/NullConst. When that is present then the domain symbols won't be empty as it will contain the symbol reflecting the proposition that the variable may be null. In a such case it's right to continue to add it as an axiom, because even "uninhabited" types may be inhabited by "null" (sadly).
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,11 @@ | ||
t8511.scala:28: warning: unreachable code | ||
??? | ||
^ | ||
t8511.scala:23: warning: match may not be exhaustive. | ||
It would fail on the following inputs: Bar(_), Baz(), EatsExhaustiveWarning(_) | ||
private def logic(head: Expr): String = head match { | ||
^ | ||
warning: 1 deprecation (since 2.13.0); re-run with -deprecation for details | ||
error: No warnings can be incurred under -Werror. | ||
3 warnings | ||
1 error |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,30 @@ | ||
// scalac: -Werror | ||
sealed trait Expr | ||
final case class Foo(other: Option[String]) extends Expr | ||
final case class Bar(someConstant: String) extends Expr | ||
final case class Baz() extends Expr | ||
final case class EatsExhaustiveWarning(other: Reference) extends Expr | ||
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sealed trait Reference { | ||
val value: String | ||
} | ||
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object Reference { | ||
def unapply(reference: Reference): Option[(String)] = { | ||
Some(reference.value) | ||
} | ||
} | ||
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object EntryPoint { | ||
def main(args: Array[String]) { | ||
println("Successfully ran") | ||
} | ||
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private def logic(head: Expr): String = head match { | ||
case Foo(_) => | ||
??? | ||
// Commenting this line only causes the exhaustive search warning to be emitted | ||
case EatsExhaustiveWarning(Reference(text)) => | ||
??? | ||
} | ||
} |