Fix #2184: Hyper Bootstrap! Integrate the backend as a git submodule

The backend lives in the scalac fork at
https://github.com/lampepfl/scala/tree/sharing-backend. Before this
commit, the scala-compiler built from this fork was a dependency of
Scala just to get this backend. This made it much more cumbersome to
test changes to the backend and also forced us to depend on Scala 2.11.5
since that is the version of scalac that the forked backend is based on.

This commit changes this by adding a git submodule in the
`scala-backend` directory that points to the scalac fork. We do not
compile the whole submodule, instead we add the subset of files we need
to the dotty-compiler project in the sbt build. See backend.md for more
information (online at
http://dotty.epfl.ch/docs/contributing/backend.html) once this commit is
merged.

The most important thing to note is that whenever you clone dotty you
should do `git clone --recursive` to also clone the submodule. If you
already have a cloned dotty you'll need to do:

git submodule update --init

You will need to repeat this command anytime you update dotty and the
backend has been updated, otherwise the content of `scala-backend` will
be stale.

1 files changed, 25 insertions, 12 deletions

diff --git a/project/Build.scala b/project/Build.scala
index 8b1c0e31e..cc6b5a6c3 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -31,8 +31,6 @@ object Build {
   val JENKINS_BUILD = "dotty.jenkins.build"
   val DRONE_MEM = "dotty.drone.mem"
 
-  val scalaCompiler = "me.d-d" % "scala-compiler" % "2.11.5-20170111-125332-40bdc7b65a"
-
   val agentOptions = List(
     // "-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005"
     // "-agentpath:/home/dark/opt/yjp-2013-build-13072/bin/linux-x86-64/libyjpagent.so"
@@ -243,6 +241,26 @@ object Build {
   // Settings shared between dotty-compiler and dotty-compiler-bootstrapped
   lazy val dottyCompilerSettings = Seq(
 
+      // The scala-backend folder is a git submodule that contains a fork of the Scala 2.11
+      // compiler developed at https://github.com/lampepfl/scala/tree/sharing-backend.
+      // We do not compile the whole submodule, only the part of the Scala 2.11 GenBCode backend
+      // that we reuse for dotty.
+      // See http://dotty.epfl.ch/docs/contributing/backend.html for more information.
+      unmanagedSourceDirectories in Compile ++= {
+        val backendDir = baseDirectory.value / ".." / "scala-backend" / "src" / "compiler" / "scala" / "tools" / "nsc" / "backend"
+        val allScalaFiles = GlobFilter("*.scala")
+
+        // NOTE: Keep these exclusions synchronized with the ones in the tests (CompilationTests.scala)
+        ((backendDir *
+          (allScalaFiles - "JavaPlatform.scala" - "Platform.scala" - "ScalaPrimitives.scala")) +++
+         (backendDir / "jvm") *
+          (allScalaFiles - "BCodeICodeCommon.scala" - "GenASM.scala" - "GenBCode.scala" - "ScalacBackendInterface.scala")
+        ).get
+      },
+
+      // Used by the backend
+      libraryDependencies += "org.scala-lang.modules" % "scala-asm" % "5.1.0-scala-2",
+
       // set system in/out for repl
       connectInput in run := true,
       outputStrategy := Some(StdoutOutput),
@@ -261,8 +279,7 @@ object Build {
 
       // get libraries onboard
       resolvers += Resolver.typesafeIvyRepo("releases"), // For org.scala-sbt:interface
-      libraryDependencies ++= Seq(scalaCompiler,
-                                  "org.scala-sbt" % "interface" % sbtVersion.value,
+      libraryDependencies ++= Seq("org.scala-sbt" % "interface" % sbtVersion.value,
                                   "org.scala-lang.modules" %% "scala-xml" % "1.0.1",
                                   "com.novocode" % "junit-interface" % "0.11" % "test",
                                   "org.scala-lang" % "scala-reflect" % scalacVersion,
@@ -394,10 +411,10 @@ object Build {
           if path.contains("scala-library") ||
             // FIXME: currently needed for tests referencing scalac internals
             path.contains("scala-reflect") ||
-            // FIXME: currently needed for tests referencing scalac internals
-            path.contains("scala-compile") ||
             // FIXME: should go away when xml literal parsing is removed
             path.contains("scala-xml") ||
+            // used for tests that compile dotty
+            path.contains("scala-asm") ||
             // needed for the xsbti interface
             path.contains("org.scala-sbt/interface/")
         } yield "-Xbootclasspath/p:" + path
@@ -631,10 +648,7 @@ object DottyInjectedPlugin extends AutoPlugin {
 
       baseDirectory in (Test,run) := (baseDirectory in `dotty-compiler`).value,
 
-      libraryDependencies ++= Seq(
-        scalaCompiler % Test,
-        "com.storm-enroute" %% "scalameter" % "0.6" % Test
-      ),
+      libraryDependencies += "com.storm-enroute" %% "scalameter" % "0.6" % Test,
 
       fork in Test := true,
       parallelExecution in Test := false,
@@ -686,8 +700,7 @@ object DottyInjectedPlugin extends AutoPlugin {
   // depend on one of these projects.
   lazy val `scala-compiler` = project.
     settings(
-      crossPaths := false,
-      libraryDependencies := Seq(scalaCompiler)
+      crossPaths := false
     ).
     settings(publishing)
   lazy val `scala-reflect` = project.