Soundness bug in structural types

[Florian3k]

Compiler version

3.2.2, 3.3.0

Minimized code

import scala.reflect.Selectable.reflectiveSelectable

class Test

def foo[A <: {def bar: Any}](ob: A) = ob.bar

@main def main = foo(new Test)

Output

Code compiles and fails at runtime with:

Exception in thread "main" java.lang.NoSuchMethodException: Test.bar()
	at java.lang.Class.getMethod(Class.java:1786)
	at scala.reflect.Selectable.applyDynamic(Selectable.scala:38)
	at scala.reflect.Selectable.applyDynamic$(Selectable.scala:11)
	at scala.reflect.Selectable$DefaultSelectable.applyDynamic(Selectable.scala:51)
	at scala.reflect.Selectable.selectDynamic(Selectable.scala:28)
	at scala.reflect.Selectable.selectDynamic$(Selectable.scala:11)
	at scala.reflect.Selectable$DefaultSelectable.selectDynamic(Selectable.scala:51)
	at v1$package$.foo(v1.scala:5)
	at v1$package$.main(v1.scala:7)
	at main.main(v1.scala:7)

Expectation

Shouldn't compile

More information

The following variants don't compile (as expected):

import scala.reflect.Selectable.reflectiveSelectable

class Test

def foo[A <: {def bar: Int}](ob: A) = ob.bar // Int instead of Any

@main def main = foo(new Test)

Result:

[error] ./v2.scala:7:22
[error] Found:    Test
[error] Required: Object{def bar: Int}
[error] @main def main = foo(new Test)
[error]                      ^^^^^^^^

import scala.reflect.Selectable.reflectiveSelectable

class Test

def foo[A <: {def bar(): Any}](ob: A) = ob.bar() // bar() instead of bar

@main def main = foo(new Test)

Result:

[error] ./v3.scala:7:22
[error] Found:    Test
[error] Required: Object{def bar(): Any}
[error] @main def main = foo(new Test)
[error]                      ^^^^^^^^

[prolativ]

The problem seems independent of Selectable:

class Test
val test: { def bar: Any } = new Test

This compiles although it shouldn't

[scala-center-bot]

This issue was picked for the Issue Spree No. 32 of 20 June 2023 which takes place in 7 days. @dwijnand, @eugenefle, @hamzaremmal, @iusildra will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.

[SethTisue]

severity level: pants on fire 🙀

well, to be fair, note that the bug is specific to the return type of bar being Any, so that's.... somewhat reassuring

as expected, Scala 2 rejects it

[mbovel]

I see now that this has been fixed. Should we find another issue for tomorrow's spree?