JavaParsers doesn't support JEP 445: Unnamed Classes and Instance Main Methods

[xuwei-k]

Compiler version

• 3.3.1
• 3.4.0-RC1-bin-20230921-3d539e6-NIGHTLY

Minimized code

Install JDK 21

A.java

void main() {
  System.out.println("hello");
}

B.scala

class B

build.sbt

javacOptions ++= Seq(
  "-Xlint:preview",
  "--enable-preview",
  "--release",
  scala.util.Properties.javaSpecVersion
)

scalaVersion := "3.3.1"

project/build.properties

sbt.version=1.9.6

sbt -J--enable-preview compile

Output

[error] 1 |void main() {
[error]   |     ^^^^
[error]   |     illegal start of type declaration
[error] one error found
[error] (Compile / compileIncremental) Compilation failed

Expectation

success compile

Note

• Scala 2 has same issue JavaParsers doesn't support JEP 445: Unnamed Classes and Instance Main Methods bug#12878
• https://openjdk.org/jeps/445

[Kordyjan]

3.3.2 will add support to JDK 21.
We will probably need to take care of handling the new main methods.

[xuwei-k]

https://openjdk.org/jeps/512 finalize in JDK 25