[WIP] Use some javac classes

This requires to start the VM with ```
--add-opens java.base/java.lang=ALL-UNNAMED
--add-opens jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED
--add-opens jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED
--add-opens jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
--add-opens jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED
--add-opens jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED
``` and other packages
settings.

Support for newer Java constructs requires to have that Java version as
BREE.

.project

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+ <name>eclipse.jdt.core</name>
+ <comment></comment>
+ <projects>
+ </projects>
+ <buildSpec>
+ <buildCommand>
+ <name>org.eclipse.m2e.core.maven2Builder</name>
+ <arguments>
+ </arguments>
+ </buildCommand>
+ </buildSpec>
+ <natures>
+ <nature>org.eclipse.m2e.core.maven2Nature</nature>
+ </natures>
+</projectDescription>

Jenkinsfile

@@ -10,7 +10,7 @@ pipeline {
  }
  tools {
  maven 'apache-maven-latest'
- jdk 'temurin-jdk17-latest'
+ jdk 'temurin-jdk20-latest'
  }
  stages {
  stage('Build') {
@@ -34,7 +34,7 @@ pipeline {
  mvn -U clean verify --batch-mode --fail-at-end -Dmaven.repo.local=$WORKSPACE/.m2/repository \
  -Ptest-on-javase-20 -Pbree-libs -Papi-check \
  -Djava.io.tmpdir=$WORKSPACE/tmp -Dproject.build.sourceEncoding=UTF-8 \
- -Dtycho.surefire.argLine="--add-modules ALL-SYSTEM -Dcompliance=1.8,11,17,20 -Djdt.performance.asserts=disabled" \
+ -Dtycho.surefire.argLine="--add-modules ALL-SYSTEM --add-exports jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED -Dcompliance=1.8,11,17,20 -Djdt.performance.asserts=disabled" \
  -Dcbi-ecj-version=99.99
  """
  }

org.eclipse.jdt.core.compiler.batch/.classpath

@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
- <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
+ <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-20">
  <attributes>
  <attribute name="module" value="true"/>
- <attribute name="limit-modules" value="java.base"/>
+ <attribute name="add-exports" value="jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED:jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED:jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED:jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED:jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED:jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED"/>
  </attributes>
  </classpathentry>
  <classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>

org.eclipse.jdt.core.compiler.batch/.settings/org.eclipse.jdt.core.prefs

@@ -25,9 +25,9 @@ org.eclipse.jdt.core.compiler.annotation.nullable=org.eclipse.jdt.annotation.Nul
 org.eclipse.jdt.core.compiler.annotation.nullanalysis=disabled
 org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
 org.eclipse.jdt.core.compiler.codegen.methodParameters=do not generate
-org.eclipse.jdt.core.compiler.codegen.targetPlatform=17
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=20
 org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
-org.eclipse.jdt.core.compiler.compliance=17
+org.eclipse.jdt.core.compiler.compliance=20
 org.eclipse.jdt.core.compiler.debug.lineNumber=generate
 org.eclipse.jdt.core.compiler.debug.localVariable=generate
 org.eclipse.jdt.core.compiler.debug.sourceFile=generate
@@ -134,7 +134,7 @@ org.eclipse.jdt.core.compiler.problem.unusedTypeParameter=ignore
 org.eclipse.jdt.core.compiler.problem.unusedWarningToken=warning
 org.eclipse.jdt.core.compiler.problem.varargsArgumentNeedCast=warning
 org.eclipse.jdt.core.compiler.release=enabled
-org.eclipse.jdt.core.compiler.source=17
+org.eclipse.jdt.core.compiler.source=20
 org.eclipse.jdt.core.formatter.align_type_members_on_columns=false
 org.eclipse.jdt.core.formatter.alignment_for_additive_operator=16
 org.eclipse.jdt.core.formatter.alignment_for_arguments_in_allocation_expression=16

org.eclipse.jdt.core.compiler.batch/META-INF/MANIFEST.MF

@@ -8,7 +8,7 @@ Bundle-ClassPath: .
 Bundle-Vendor: Eclipse.org
 Automatic-Module-Name: org.eclipse.jdt.core.compiler.batch
 Bundle-ActivationPolicy: lazy
-Bundle-RequiredExecutionEnvironment: JavaSE-17
+Bundle-RequiredExecutionEnvironment: JavaSE-20
 Export-Package: META-INF.services,
  org.eclipse.jdt.core.compiler,
  org.eclipse.jdt.core.compiler.batch,

org.eclipse.jdt.core.compiler.batch/build.properties

@@ -21,4 +21,4 @@ src.includes = about.html,\
  META-INF/services/,\
  META-INF/eclipse.inf,\
  grammar/
-jars.extra.classpath = lib/javax20api.jar,platform:/plugin/org.apache.ant/lib/ant.jar
+jars.extra.classpath = platform:/plugin/org.apache.ant/lib/ant.jar

org.eclipse.jdt.core.compiler.batch/pom.xml

@@ -28,6 +28,18 @@
 
  <build>
  <plugins>
+ <plugin>
+ <groupId>org.eclipse.tycho</groupId>
+ <artifactId>tycho-compiler-plugin</artifactId>
+ <configuration>
+ <deriveReleaseCompilerArgumentFromTargetLevel>false</deriveReleaseCompilerArgumentFromTargetLevel>
+ <release></release>
+ <compilerArgs>
+ <arg>--add-exports</arg>
+ <arg>jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED</arg>
+ </compilerArgs>
+ </configuration>
+ </plugin>
  <plugin>
  <artifactId>maven-antrun-plugin</artifactId>
  <executions>