Regression: inferred types with @retains cause previous macro implementations to crash #24006
Description
Found in https://github.com/VirtusLab/community-build3/actions/runs/17687960136/job/50279371271
Compiler version
3.8.0-RC1-bin-20250912-c4c48e3-NIGHTLY
Minimized code
@main def main() = eval(List(1) :+ 4)import scala.quoted._
inline def eval[T](x: List[T]) = ${ evalImpl[T]('x) }
def evalImpl[A](x: Expr[List[A]])(using Quotes): Expr[Unit] =
import quotes.reflect.*
println(x.asTerm.tpe.widen)
x.asTerm.tpe.widen.typeArgs.head
'{()}
Output
AnnotatedType(AppliedType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class collection)),object immutable),class List),List(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Int))),ConcreteAnnotation(Apply(TypeApply(Select(New(Select(Select(Select(Ident(_root_),scala),annotation),retains)),<init>),List(SingletonTypeTree(This(Ident())))),List())))-- Error: /Users/jchyb/workspace/community-build3/repo/a.scala:1:23 ------------
1 |@main def main() = eval(List(1) :+ 4)
| ^^^^^^^^^^^^^^^^^^
| Exception occurred while executing macro expansion.
| java.util.NoSuchElementException: head of empty list
| at scala.collection.immutable.Nil$.head(List.scala:669)
| at scala.collection.immutable.Nil$.head(List.scala:669)
| at b$package$.evalImpl(b.scala:7)
|
|-----------------------------------------------------------------------------
|Inline stack trace
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|This location contains code that was inlined from b.scala:3
3 |inline def eval[T](x: List[T]) = ${ evalImpl[T]('x) }
| ^^^^^^^^^^^^^^^^^^^^
-----------------------------------------------------------------------------Expectation
Ideally behavior like in 3.7.3, and before:
Output:
AppliedType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class collection)),object immutable),class List),List(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Int)))and no crash.
Would it be possible to not have the retains when we use capture checking? I wonder if it's even intentional here, considerng :+ must be used to trigger it (I do not know much about capture checking yet).