Undefined += in inner quote

[nicolasstucki]

Implementing scala.quoted.ExprOps.toExprOfList with

    /** Lifts this list of expressions into an expression of a list
     *
     *  Transforms a list of expression
     *    `e1 :: e2 :: ... :: Nil` where `ei: Expr[T]`
     *  to an expression equivalent to
     *    `'{ $e1 :: $e2 :: ... :: Nil }` typed as an `Expr[List[T]]`
     */
    def (list: List[Expr[T]]) toExprOfList[T] given Type[T], QuoteContext: Expr[List[T]] = '{
      val buff = List.newBuilder[T]
      ${ Expr.block(list.map(v => '{ buff +=  $v }), '{ buff.result() }) }
    }

fails with

35 |      ${ Expr.block(list.map(v => '{ buff `+=` $v }), '{ buff.result() }) }
   |                                     ^^^^^^^^^^^^
   |                                 undefined: buff.+= # 189467: TermRef(TermRef(NoPrefix,val buff),+=) at frontend
   | This location is in code that was inlined at quoted_2.scala:6

[nicolasstucki]

This might be related to #7110

[nicolasstucki]

Self contained version:

import scala.quoted._

object Macros {

  inline def m() : Any = ${  mImpl() }

  def mImpl()(using QuoteContext): Expr[Any] =
    List(Expr(1), Expr(2), Expr(3)).toExprOfList

  def (list: List[Expr[T]]).toExprOfList[T](using Type[T], QuoteContext): Expr[List[T]] = '{
    val buff = List.newBuilder[T]
    ${ Expr.block(list.map(v => '{ buff +=  $v }), '{ buff.result() }) }
  }
}

import scala.quoted._
import Macros._

object Test {
  def main(args: Array[String]): Unit = {
    println(m())
  }
}

[liufengyun]

The error now is different, it complains phase consistency for T. Maybe it is simpler to fix? /ping @nicolasstucki