Referencing a tree of an inner class leads to a ClassCastException #19732
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lbialy
added
itype:bug
itype:crash
stat:needs triage
Kordyjan
added
area:metaprogramming:quotes
nicolasstucki
assigned Kordyjan, mbovel and jchyb and unassigned jchyb, Kordyjan and mbovel
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Minimised: class Outer:
case class Inner(b: Int = 23) derives Defaultsimport scala.quoted.*
trait Defaults[A]:
def defaults: Map[String, Any]
object Defaults:
inline def derived[A <: Product]: Defaults[A] = ${ defaultsImpl[A] }
def defaultsImpl[A <: Product: Type](using Quotes): Expr[Defaults[A]] =
'{
new Defaults[A]:
def defaults: Map[String, Any] = ${ defaultParmasImpl[A] }
}
inline def defaultParams[T]: Map[String, Any] = ${ defaultParmasImpl[T] }
def defaultParmasImpl[T](using quotes: Quotes, tpe: Type[T]): Expr[Map[String, Any]] =
import quotes.reflect.*
TypeRepr.of[T].classSymbol match
case None => '{ Map.empty[String, Any] }
case Some(sym) =>
val comp = sym.companionClass
Ref(sym.companionModule)
'{???}With that said, we can also produce a compiler crash in erasure without any class Outer:
case class Inner(b: Int = 23)
@main def test(): Unit =
val outer = Outer()
defaultParams[outer.Inner]import scala.quoted.*
inline def defaultParams[T]: Map[String, Any] = ${ defaultParmasImpl[T] }
def defaultParmasImpl[T](using quotes: Quotes, tpe: Type[T]): Expr[Map[String, Any]] =
import quotes.reflect.*
TypeRepr.of[T].classSymbol match
case None => '{ Map.empty[String, Any] }
case Some(sym) =>
val comp = sym.companionClass
val mod = Ref(sym.companionModule)
val names =
for p <- sym.caseFields if p.flags.is(Flags.HasDefault)
yield p.name
val namesExpr: Expr[List[String]] =
Expr.ofList(names.map(Expr(_)))
val body = comp.tree.asInstanceOf[ClassDef].body
val idents: List[Ref] =
for
case deff @ DefDef(name, _, _, _) <- body
if name.startsWith("$lessinit$greater$default")
yield mod.select(deff.symbol)
val typeArgs = TypeRepr.of[T].typeArgs
val identsExpr: Expr[List[Any]] =
if typeArgs.isEmpty then Expr.ofList(idents.map(_.asExpr))
else Expr.ofList(idents.map(_.appliedToTypes(typeArgs).asExpr))
'{ $namesExpr.zip($identsExpr).toMap } |
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The second minimisation I prepared above is a separate issue, where after getting a symbol of a path dependent TypeRepr we lose information about the prefix there, changing back to a typeref we find out that it is now prefixed by |
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Submitted the issue: #19933 |
nicolasstucki
added a commit
that referenced
this issue
Mar 14, 2024
#19930) In the issue minimisation, `tpd.ref` returns a tpd.This(Ident(Inner$)) tree, where the inner ident is a type ident, which was unexpected. Trying to adjust the `tpd.ref` to return a RefType for that case seems dangerous, so I instead opted for a workaround directly inside the QuotesImpl. At first I wanted to reuse the `tpd.This` tree somehow (or at least to use a correctly retyped `Ident`), but nothing I tried with it worked, so I ended up writing the correct Ref by hand. Fixes #19732
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@Kordyjan is this getting a backport to 3.3.x? |
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It was backported, can be tried with 3.3.4-RC1 |
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Awesome, both besom and scala-yaml have the workaround. I'll test on 3.3.4-RC1. |
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Compiler version
3.3.1
Minimized code
This is a slightly changed code from https://github.com/lampepfl/dotty-macro-examples/tree/main/defaultParamsInference, two files as in the example:
macro.scala:
dummy.scala:
How to run:
scala-cli run . -S 3.3.1 --server=falseFor some reason this does not happen when using the
defaultParamsmacro directly but does happen if the same macro is executed via macro called byderives. Only happens for inner classes, other cases seem to work fine.Output (click arrow to expand)
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