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Avoid erasure/preErasure issues around Any in transformIsInstanceOf #21647

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Avoid erasure/preErasure issues around Any in transformIsInstanceOf #21647

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6 changes: 5 additions & 1 deletion compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -358,7 +358,11 @@ object TypeTestsCasts {
report.error(em"$untestable cannot be used in runtime type tests", tree.srcPos)
constant(expr, Literal(Constant(false)))
case _ =>
val erasedTestType = erasure(testType)
val erasedTestType =
if testType.isAny && expr.tpe.isPrimitiveValueType then
defn.AnyValType
Comment on lines +362 to +363
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Isn't that going to trigger with the same issue with any other type that erases to Object? Like ... AnyVal itself?

There's supposed to already be logic in transformIsInstanceOf to avoid a type test when expr.tpe <:< testType:

scala3/compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala

Lines 259 to 261 in 9961e70

if (expr.tpe <:< testType) && inMatch then
if expr.tpe.isNotNull then constant(expr, Literal(Constant(true)))
else expr.testNotNull

The problem is that it tests on erased types, instead of the original types. Addressing that at the root should be more robust, shouldn't it?

else
erasure(testType)
transformIsInstanceOf(expr, erasedTestType, erasedTestType, flagUnrelated)
}

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2 changes: 2 additions & 0 deletions tests/pos/i21544.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
class Test():
def m1(xs: List[Boolean]) = for (x: Any) <- xs yield x
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