7 files changed, 61 insertions, 10 deletions
diff --git a/src/dotty/tools/dotc/Compiler.scala b/src/dotty/tools/dotc/Compiler.scala
index f12ab66c5..be4477ee2 100644
--- a/src/dotty/tools/dotc/Compiler.scala
+++ b/src/dotty/tools/dotc/Compiler.scala
@@ -16,6 +16,7 @@ import core.DenotTransformers.DenotTransformer
 import core.Denotations.SingleDenotation
 
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode}
+import dotty.tools.backend.sjs.GenSJSIR
 
 class Compiler {
 
@@ -82,6 +83,7 @@ class Compiler {
       List(new ExpandPrivate,
            new CollectEntryPoints,
            new LabelDefs),
+      List(new GenSJSIR),
       List(new GenBCode)
     )
 
@@ -99,8 +101,17 @@ class Compiler {
    *    imports      For each element of RootImports, an import context
    */
   def rootContext(implicit ctx: Context): Context = {
-    ctx.definitions.init(ctx)
-    ctx.setPhasePlan(phases)
+    ctx.initialize()(ctx)
+    val actualPhases = if (ctx.settings.scalajs.value) {
+      phases
+    } else {
+      // Remove Scala.js-related phases
+      phases.mapConserve(_.filter {
+        case _: GenSJSIR => false
+        case _ => true
+      }).filter(_.nonEmpty)
+    }
+    ctx.setPhasePlan(actualPhases)
     val rootScope = new MutableScope
     val bootstrap = ctx.fresh
       .setPeriod(Period(nextRunId, FirstPhaseId))
@@ -111,7 +122,7 @@ class Compiler {
       .setTyper(new Typer)
       .setMode(Mode.ImplicitsEnabled)
       .setTyperState(new MutableTyperState(ctx.typerState, ctx.typerState.reporter, isCommittable = true))
-    ctx.definitions.init(start) // set context of definitions to start
+    ctx.initialize()(start) // re-initialize the base context with start
     def addImport(ctx: Context, refFn: () => TermRef) =
       ctx.fresh.setImportInfo(ImportInfo.rootImport(refFn)(ctx))
     (start.setRunInfo(new RunInfo(start)) /: defn.RootImportFns)(addImport)
diff --git a/src/dotty/tools/dotc/config/SJSPlatform.scala b/src/dotty/tools/dotc/config/SJSPlatform.scala
new file mode 100644
index 000000000..fec9c25a1
--- /dev/null
+++ b/src/dotty/tools/dotc/config/SJSPlatform.scala
@@ -0,0 +1,13 @@
+package dotty.tools.dotc.config
+
+import dotty.tools.dotc.core._
+import Contexts._
+
+import dotty.tools.backend.sjs.JSDefinitions
+
+class SJSPlatform()(implicit ctx: Context) extends JavaPlatform {
+
+  /** Scala.js-specific definitions. */
+  val jsDefinitions: JSDefinitions = new JSDefinitions()
+
+}
diff --git a/src/dotty/tools/dotc/config/ScalaSettings.scala b/src/dotty/tools/dotc/config/ScalaSettings.scala
index 65bc9ba23..aa264329c 100644
--- a/src/dotty/tools/dotc/config/ScalaSettings.scala
+++ b/src/dotty/tools/dotc/config/ScalaSettings.scala
@@ -29,6 +29,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val target = ChoiceSetting("-target", "target", "Target platform for object files. All JVM 1.5 targets are deprecated.",
     List("jvm-1.5", "jvm-1.5-fjbg", "jvm-1.5-asm", "jvm-1.6", "jvm-1.7", "jvm-1.8", "msil"),
     "jvm-1.8")
+  val scalajs = BooleanSetting("-scalajs", "Compile in Scala.js mode (requires scalajs-library.jar on the classpath).")
   val unchecked = BooleanSetting("-unchecked", "Enable additional warnings where generated code depends on assumptions.")
   val uniqid = BooleanSetting("-uniqid", "Uniquely tag all identifiers in debugging output.")
   val usejavacp = BooleanSetting("-usejavacp", "Utilize the java.class.path in classpath resolution.")
diff --git a/src/dotty/tools/dotc/core/Contexts.scala b/src/dotty/tools/dotc/core/Contexts.scala
index f0537dffa..2fc958a49 100644
--- a/src/dotty/tools/dotc/core/Contexts.scala
+++ b/src/dotty/tools/dotc/core/Contexts.scala
@@ -26,7 +26,7 @@ import reporting._
 import collection.mutable
 import collection.immutable.BitSet
 import printing._
-import config.{Settings, ScalaSettings, Platform, JavaPlatform}
+import config.{Settings, ScalaSettings, Platform, JavaPlatform, SJSPlatform}
 import language.implicitConversions
 import DenotTransformers.DenotTransformer
 
@@ -514,8 +514,21 @@ object Contexts {
     /** The symbol loaders */
     val loaders = new SymbolLoaders
 
+    /** The platform, initialized by `initPlatform()`. */
+    private var _platform: Platform = _
+
     /** The platform */
-    val platform: Platform = new JavaPlatform
+    def platform: Platform = {
+      if (_platform == null) {
+        throw new IllegalStateException(
+            "initialize() must be called before accessing platform")
+      }
+      _platform
+    }
+
+    protected def newPlatform(implicit ctx: Context): Platform =
+      if (settings.scalajs.value) new SJSPlatform
+      else new JavaPlatform
 
     /** The loader that loads the members of _root_ */
     def rootLoader(root: TermSymbol)(implicit ctx: Context): SymbolLoader = platform.rootLoader(root)
@@ -526,6 +539,14 @@ object Contexts {
     /** The standard definitions */
     val definitions = new Definitions
 
+    /** Initializes the `ContextBase` with a starting context.
+     *  This initializes the `platform` and the `definitions`.
+     */
+    def initialize()(implicit ctx: Context): Unit = {
+      _platform = newPlatform
+      definitions.init
+    }
+
     def squashed(p: Phase): Phase = {
       allPhases.find(_.period.containsPhaseId(p.id)).getOrElse(NoPhase)
     }
diff --git a/src/dotty/tools/dotc/transform/LinkScala2ImplClasses.scala b/src/dotty/tools/dotc/transform/LinkScala2ImplClasses.scala
index 60e8edc26..ca06938dc 100644
--- a/src/dotty/tools/dotc/transform/LinkScala2ImplClasses.scala
+++ b/src/dotty/tools/dotc/transform/LinkScala2ImplClasses.scala
@@ -48,11 +48,15 @@ class LinkScala2ImplClasses extends MiniPhaseTransform with IdentityDenotTransfo
     }
   }
 
-  private def implMethod(meth: Symbol)(implicit ctx: Context): Symbol =
-    meth.owner.implClass.info
-      .decl(if (meth.isConstructor) nme.TRAIT_CONSTRUCTOR else meth.name)
+  private def implMethod(meth: Symbol)(implicit ctx: Context): Symbol = {
+    val implInfo = meth.owner.implClass.info
+    if (meth.isConstructor)
+      implInfo.decl(nme.TRAIT_CONSTRUCTOR).symbol
+    else
+      implInfo.decl(meth.name)
       .suchThat(c => FullParameterization.memberSignature(c.info) == meth.signature)
       .symbol
+  }
 
   private val Scala2xTrait = allOf(Scala2x, Trait)
-}
-\ No newline at end of file
+}
diff --git a/src/dotty/tools/dotc/transform/Memoize.scala b/src/dotty/tools/dotc/transform/Memoize.scala
index fbf8ed763..b775496ae 100644
--- a/src/dotty/tools/dotc/transform/Memoize.scala
+++ b/src/dotty/tools/dotc/transform/Memoize.scala
@@ -91,6 +91,7 @@ import Decorators._
         }
       } else if (sym.isSetter) {
         if (!sym.is(ParamAccessor)) { val Literal(Constant(())) = tree.rhs } // this is intended as an assertion
+        field.setFlag(Mutable) // necessary for vals mixed in from Scala2 traits
         val initializer = Assign(ref(field), ref(tree.vparamss.head.head.symbol))
         cpy.DefDef(tree)(rhs = transformFollowingDeep(initializer)(ctx.withOwner(sym), info))
       }
diff --git a/src/dotty/tools/dotc/transform/Pickler.scala b/src/dotty/tools/dotc/transform/Pickler.scala
index 8040c86d4..c5b223d53 100644
--- a/src/dotty/tools/dotc/transform/Pickler.scala
+++ b/src/dotty/tools/dotc/transform/Pickler.scala
@@ -80,7 +80,7 @@ class Pickler extends Phase {
 
   private def testUnpickler(units: List[CompilationUnit])(implicit ctx: Context): Unit = {
     pickling.println(i"testing unpickler at run ${ctx.runId}")
-    ctx.definitions.init
+    ctx.initialize()
     val unpicklers =
       for (unit <- units; (cls, pickler) <- unit.picklers) yield {
         val unpickler = new DottyUnpickler(pickler.assembleParts())