Stop using the bootclasspath for Java 9 compatibility

It's no longer introspectable under Java 9. The scalac 2.12 shell scripts work
around this by passing the bootclasspath jars as an additional system
property, but we can avoid this complication by just using -classpath instead.
This may have a slight negative impact on startup performance since the
JVM bytecode verifier is not run for classes from the bootclasspath, but
we can worry about that later.

Author: smarter

bench/src/main/scala/Benchmarks.scala

@@ -37,7 +37,7 @@ object Bench {
     val libs = System.getProperty("BENCH_CLASS_PATH")
 
     val opts = new OptionsBuilder()
-               .jvmArgsPrepend("-Xbootclasspath/a:" + libs + ":", "-Xms2G", "-Xmx2G")
+               .jvmArgsPrepend(s"-classpath $libs", "-Xms2G", "-Xmx2G")
                .mode(Mode.AverageTime)
                .timeUnit(TimeUnit.MILLISECONDS)
                .warmupIterations(warmup)

compiler/test/dotty/Jars.scala

@@ -2,6 +2,9 @@ package dotty
 
 /** Jars used when compiling test, normally set from the sbt build */
 object Jars {
+  def scalaLibrary: String = sys.env.get("DOTTY_SCALA_LIBRARY")
+    .getOrElse(findJarFromRuntime("scala-library"))
+
   /** Dotty library Jar */
   val dottyLib: String = sys.env.get("DOTTY_LIB")
     .getOrElse(Properties.dottyLib)
@@ -36,14 +39,12 @@ object Jars {
 
   /** Dotty test dependencies */
   val dottyTestDeps: List[String] =
-    dottyLib :: dottyCompiler :: dottyInterfaces :: jlineTerminal :: jlineReader :: dottyExtras
+    scalaLibrary :: dottyLib :: dottyCompiler :: dottyInterfaces :: jlineTerminal :: jlineReader :: dottyExtras
 
   /** Dotty runtime with compiler dependencies, used for quoted.Expr.run */
   lazy val dottyRunWithCompiler: List[String] =
-    dottyLib :: dottyCompiler :: dottyInterfaces :: scalaAsm :: Nil
+    scalaLibrary :: dottyLib :: dottyCompiler :: dottyInterfaces :: scalaAsm :: Nil
 
-  def scalaLibrary: String = sys.env.get("DOTTY_SCALA_LIBRARY")
-    .getOrElse(findJarFromRuntime("scala-library"))
 
   /** Gets the scala 2.* library at runtime, note that doing this is unsafe
    *  unless you know that the library will be on the classpath of the running

dist/bin/dotc

@@ -28,7 +28,6 @@ fi
 source "$PROG_HOME/bin/common"
 
 default_java_opts="-Xmx768m -Xms768m"
-bootcp=true
 withCompiler=true
 
 CompilerMain=dotty.tools.dotc.Main
@@ -70,11 +69,7 @@ classpathArgs () {
   toolchain+="$JLINE_TERMINAL$PSEP"
   toolchain+="$JLINE_TERMINAL_JNA"
 
-  if [[ -n "$bootcp" ]]; then
-    jvm_cp_args="-Xbootclasspath/a:\"$toolchain\""
-  else
-    jvm_cp_args="-classpath \"$toolchain\""
-  fi
+  jvm_cp_args="-classpath \"$toolchain\""
 }
 
 while [[ $# -gt 0 ]]; do
@@ -92,8 +87,6 @@ case "$1" in
    -decompile) PROG_NAME="$DecompilerMain" && shift ;;
  -print-tasty) PROG_NAME="$DecompilerMain" && addScala "-print-tasty" && shift ;;
          -run) PROG_NAME="$ReplMain" && shift ;;
-      -bootcp) bootcp=true && shift ;;
-   -nobootcp) unset bootcp && shift ;;
       -colors) colors=true && shift ;;
    -no-colors) unset colors && shift ;;
   -with-compiler) jvm_cp_args="$PSEP$DOTTY_COMP" && shift ;;

project/Build.scala

@@ -223,9 +223,6 @@ object Build {
     // non-bootstrapped dotty-library that will then take priority over
     // the bootstrapped dotty-library on the classpath or sourcepath.
     classpathOptions ~= (_.withAutoBoot(false)),
-    // We still need a Scala bootclasspath equal to the JVM bootclasspath,
-    // otherwise sbt 0.13 incremental compilation breaks (https://github.com/sbt/sbt/issues/3142)
-    scalacOptions ++= Seq("-bootclasspath", sys.props("sun.boot.class.path")),
 
     // Enforce that the only Scala 2 classfiles we unpickle come from scala-library
     /*
@@ -551,22 +548,22 @@ object Build {
         val attList = (dependencyClasspath in Runtime).value
         val jars = packageAll.value
 
-        // put needed dependencies on classpath:
-        val path = for {
-          file <- attList.map(_.data)
-          path = file.getAbsolutePath
-          // FIXME: when we snip the cord, this should go bye-bye
-          if path.contains("scala-library") ||
-            // FIXME: currently needed for tests referencing scalac internals
-            path.contains("scala-reflect") ||
-            // used for tests that compile xml
-            path.contains("scala-xml") ||
-            // used for tests that compile dotty
-            path.contains("scala-asm") ||
-            // needed for the xsbti interface
-            path.contains("compiler-interface") ||
-            path.contains("util-interface")
-        } yield "-Xbootclasspath/p:" + path
+        // // put needed dependencies on classpath:
+        // val path = for {
+        //   file <- attList.map(_.data)
+        //   path = file.getAbsolutePath
+        //   // FIXME: when we snip the cord, this should go bye-bye
+        //   if path.contains("scala-library") ||
+        //     // FIXME: currently needed for tests referencing scalac internals
+        //     path.contains("scala-reflect") ||
+        //     // used for tests that compile xml
+        //     path.contains("scala-xml") ||
+        //     // used for tests that compile dotty
+        //     path.contains("scala-asm") ||
+        //     // needed for the xsbti interface
+        //     path.contains("compiler-interface") ||
+        //     path.contains("util-interface")
+        // } yield "-Xbootclasspath/p:" + path
 
         val ci_build = // propagate if this is a ci build
           sys.props.get("dotty.drone.mem") match {
@@ -586,7 +583,7 @@ object Build {
           "-Ddotty.tests.classes.compiler=" + jars("dotty-compiler")
         )
 
-        jarOpts ::: tuning ::: agentOptions ::: ci_build ::: path.toList
+        jarOpts ::: tuning ::: agentOptions ::: ci_build
       },
 
       testCompilation := testOnlyFiltered("dotty.tools.dotc.*CompilationTests", "--exclude-categories=dotty.SlowTests").evaluated,
@@ -661,7 +658,9 @@ object Build {
   )
 
   def runCompilerMain(repl: Boolean = false) = Def.inputTaskDyn {
+    val attList = (dependencyClasspath in Runtime).value
     val jars = packageAll.value
+    val scalaLib = findLib(attList, "scala-library")
     val dottyLib = jars("dotty-library")
     val dottyCompiler = jars("dotty-compiler")
     val args0: List[String] = spaceDelimited("<arg>").parsed.toList
@@ -677,7 +676,7 @@ object Build {
       else if (debugFromTasty) "dotty.tools.dotc.fromtasty.Debug"
       else "dotty.tools.dotc.Main"
 
-    var extraClasspath = dottyLib
+    var extraClasspath = s"$scalaLib:$dottyLib"
     if ((decompile || printTasty) && !args.contains("-classpath")) extraClasspath += ":."
     if (args0.contains("-with-compiler")) {
       if (!isDotty.value) {