Unhelpful error message when using named patterns with custom selector type in extractor match

[SrTobi]

Compiler version

3.7.1-RC1-bin-20250328-d519790-NIGHTLY

Minimized example

class CustomProduct(x: Int) extends Product {
  def _1 = someName
  def _2 = blub

  val someName = x + 5
  val blub = "blub"

  override def canEqual(that: Any): Boolean = ???
}

object ProductMatch {
  def unapply(x: Int): CustomProduct = new CustomProduct(x)
}

@main
def run = {
  3 match {
    case ProductMatch(someName = x) => println (x)
  }
}

Output Error/Warning message

No element named `someName` is defined in selector type CustomProduct
    case ProductMatch(someName = x) => println (x)

Why this Error/Warning was not helpful

The message was unhelpful because there is actually an element called someName on CustomProduct.

Suggested improvement

I think the message should be something more like

CustomProduct is not a valid selector type for the use with named patterns.
Only named tuples and case classes can be used with named patterns.

[SrTobi]

I found this while implementing the logic in IntelliJ. Pls ping me if some underlying concept changes (like allowing named patterns on custom selector types)

[mbovel]

This issue was picked for today's Scala Issue Spree. @jan-pieter, @nmcb, @RoccoMathijn, Thijs and Wessel will be working on it! If you have any insight into the issue or guidance on how to fix it, please leave it here.

[jan-pieter]

@thijsnissen @wwbakker ^