Github user drewrobb commented on a diff in the pull request:
https://github.com/apache/spark/pull/23062#discussion_r234834125
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala
---
@@ -788,12 +788,37 @@ object ScalaReflection extends ScalaReflection {
}
/**
- * Finds an accessible constructor with compatible parameters. This is a
more flexible search
- * than the exact matching algorithm in `Class.getConstructor`. The
first assignment-compatible
- * matching constructor is returned. Otherwise, it returns `None`.
+ * Finds an accessible constructor with compatible parameters. This is a
more flexible search than
+ * the exact matching algorithm in `Class.getConstructor`. The first
assignment-compatible
+ * matching constructor is returned if it exists. Otherwise, we check
for additional compatible
+ * constructors defined in the companion object as `apply` methods.
Otherwise, it returns `None`.
*/
- def findConstructor(cls: Class[_], paramTypes: Seq[Class[_]]):
Option[Constructor[_]] = {
- Option(ConstructorUtils.getMatchingAccessibleConstructor(cls,
paramTypes: _*))
+ def findConstructor(cls: Class[_], paramTypes: Seq[Class[_]]):
Option[Seq[AnyRef] => Any] = {
--- End diff --
Real fast I get:
```
[error]
/home/drew/spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala:798:
type mismatch;
[error] found : _$31 where type _$31
[error] required: T
[error] case Some(c) => Some((x: Seq[AnyRef]) => c.newInstance(x: _*))
[error] ^
[error]
/home/drew/spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala:818:
type mismatch;
[error] found : Any
[error] required: T
[error] method.apply(args: _*)
[error]
```
`Constructor` has a type parameter, but the signature of `newInstance`
doesn't use it, and in the second case `method.apply` method returned by
reflection has a return type of `Any`. I think that can only be resolved with
adding `asInstanceOf[Seq[AnyRef] => T]`, which I don't think would be any
better (unless I'm missing something)?
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