Backport: Fix isInstanceOf[Array[?]] returning true on non-Array #12108
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Before this commit, the `MultiArrayOf(elem, ndims)` extractor used to
strip wildcards from the element type, this was surprising since it does
not match what the `ArrayOf(elem)` extractor does, and lead to a bug in
`TypeTestCasts.interceptTypeApply` which contains the following code:
case defn.MultiArrayOf(elem, ndims) if isGenericArrayElement(elem, isScala2 = false) =>
`isGenericArrayElement` returns false for `Any` but true for
`_ >: Nothing <: Any`, so the stripped wildcard means that this case was
skipped, resulting in:
x.isInstanceOf[Array[?]]
being erased to:
x.isInstanceOf[Object]
instead of:
scala.runtime.ScalaRunTime.isArray(x, 1)
Fixed by tweaking `MultiArrayOf` to keep any final wildcard around like
`ArrayOf` does.
nicolasstucki
approved these changes
Apr 16, 2021
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This is a backport of #12103