scala.tools.nsc.javac.JavaParsers can't parse JDK17 "Sealed Classes"

[xuwei-k]

reproduction steps

https://openjdk.java.net/jeps/360
https://github.com/scala/scala/blob/v2.13.3/src/compiler/scala/tools/nsc/javac/JavaParsers.scala#L1002

$ java --version
openjdk 15 2020-09-15
OpenJDK Runtime Environment (build 15+36-1562)
OpenJDK 64-Bit Server VM (build 15+36-1562, mixed mode, sharing)

build.sbt

javacOptions ++= Seq("--enable-preview", "--release", "15")

scalaVersion := "2.13.3"

A.java

sealed class A{}

final class B extends A{}

C.scala

class C

sbt version: 1.3.13

problem

run sbt compile

A.java:1:8: illegal start of type declaration
[error] sealed class A{}
[error]        ^
[error] one error found
[error] (Compile / compileIncremental) Compilation failed
[error] Total time: 0 s, completed 2020/09/22 10:18:53

workaround

// build.sbt
compileOrder := CompileOrder.JavaThenScala

note

similar issue #11908

[mkurz]

Not really sure if this is somehow related, but ASM 9.0, which brings support for Java 15 and even Java 16 already just got released:

• https://gitlab.ow2.org/asm/asm/-/tags/ASM_9_0
• https://repo1.maven.org/maven2/org/ow2/asm/asm/9.0/
• https://asm.ow2.io/versions.html

[SethTisue]

@mkurz this ticket is about mixed compilation of Scala and Java sources. ASM involves JVM bytecode only, not Java source code.

(regardless, thanks for calling the ASM upgrade to our attention, we'll evaluate that soon, plus I'll be embarking on scala/community-build#1225 soon.)

[SethTisue]

it would make sense to tackle this and #12171 together

[mkurz]

@SethTisue Please also don't forget #11908 😉

[mkurz]

Sealed Classes (JEP 409) was just merged into the Java 17 dev repo:

• 8260517: implement Sealed Classes as a standard feature in Java openjdk/jdk#3526
  • Commit: openjdk/jdk@0fa9223
• 8265319: implement Sealed Classes as a standard feature in Java, javax.lang.model changes openjdk/jdk#3528
  • Commit: openjdk/jdk@31b98e1
• 8265684: implement Sealed Classes as a standard feature in Java, javadoc changes openjdk/jdk#3613
  • Commit: openjdk/jdk@7dcb9fd

Also see https://openjdk.java.net/projects/jdk/17/