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Fix #10116: Fix adaptConstant to that it survives Ycheck #10280

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Merged
merged 2 commits into from
Nov 11, 2020
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Fix #10116: Fix adaptConstant to that it survives Ycheck #10280

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26d6203
Fix #10116: Fix adaptConstant to that it survives Ycheck
odersky Nov 11, 2020
2be0eca
Address review comments
odersky Nov 11, 2020
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -3425,7 +3425,7 @@ class Typer extends Namer
// try converting a constant to the target type
val folded = ConstFold(tree, pt)
if (folded ne tree)
return adaptConstant(folded, folded.tpe.asInstanceOf[ConstantType])
return adaptConstant(tree, folded.tpe.asInstanceOf[ConstantType])
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Hum. Looking at this fix and at ConstFold.apply(tree, pt), I think the latter basically produces an invalid tree, that is never safe to reuse.

I also see that ConstFold.Apply(tree, pt) is used only here. With the fix, we are therefore patching the invalid result of ConstFold.apply at its only call site; but if someone starts calling that overload somewhere else, they will likely reintroduce a similar bug.

Consider inlining the contents of that overload of ConstFold(tree, tp) here instead. Once you do that, you won't have to create that transient invalid tree, since you'll be able to directly use x.convertTo(tp) instead of folded.tpe.

This would prevent further invalid uses of that overload.


val captured = captureWildcards(wtp)
if (captured `ne` wtp)
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18 changes: 18 additions & 0 deletions tests/pos/i10116.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
object OverloadedWithLong {
def overloaded(x: Long): Any =
x

def overloaded(x: Any): Unit =
???
}

object Test {
def main(args: Array[String]): Unit =
import OverloadedWithLong._

val l: Any = 0 :: Nil
val r = overloaded(l match {
case x :: xs => 5
})
assert(r == 5L)
}