Incorrect erasure for intersection type in Java method

[tpolecat]

Compiler version

3.0.0

Minimized code

Add dependency "org.testcontainers" % "testcontainers" % "1.15.2" and then try the following:

scala> new org.testcontainers.images.builder.ImageFromDockerfile().withFileFromClasspath("foo", "bar")                                                                                                                   
java.lang.NoSuchMethodError: 'org.testcontainers.images.builder.traits.BuildContextBuilderTrait org.testcontainers.images.builder.ImageFromDockerfile.withFileFromClasspath(java.lang.String, java.lang.String)'
  ... 38 elided

The method in question is defined here.

Scala 2.13 generates the following instruction:

      16: invokeinterface #45,  3           // InterfaceMethod org/testcontainers/images/builder/traits/ClasspathTrait.withFileFromClasspath:(Ljava/lang/String;Ljava/lang/String;)Lorg/testcontainers/images/builder/traits/ClasspathTrait;

Scala 3.0 generates the following, which differs in the return type.

      18: invokeinterface #34,  3           // InterfaceMethod org/testcontainers/images/builder/traits/ClasspathTrait.withFileFromClasspath:(Ljava/lang/String;Ljava/lang/String;)Lorg/testcontainers/images/builder/traits/BuildContextBuilderTrait;

[smarter]

Huh, looks like I misread https://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.4, somehow I was convinced the first operand of a Java intersection had to be a class and could not be an interface, and therefore designed our intersection erasure algorithm around this (#11808). Turns out that's completely false and now that 3.0 is out it's too late to change how we do intersection erasure, so we'll have to add a special case for Java intersection erasure (but I guess that was inevitable since we can't at the same time have commutativity and match the Java erasure semantics, oh well).

[smarter]

Oh man, looking at testcontainers/testcontainers-scala#177 it looks like the problem was known before 3.0.0 was out, so if only we had known about it then, we could have potentially redesigned our erasure algorithm in time, whereas now we're stuck with it until Scala 4. Sadness.

[tpolecat]

Yep, sorry. Nobody looked at it closely until an hour ago. :-(