Half of an implementation of sealedness for jav...

Half of an implementation of sealedness for java enums. Since it's only
half it's behind -Xexperimental, but it works like a charm for the half
where it works (that being compiling against bytecode.) Need input on
how to approach the source half. References ticket #2442. Review by
moors.

5 files changed, 39 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index c2136edbb6..0f05a7fcce 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -222,6 +222,7 @@ class Global(var settings: Settings, var reporter: Reporter) extends SymbolTable
 
     def debug         = settings.debug.value
     def deprecation   = settings.deprecation.value
+    def experimental  = settings.Xexperimental.value
     def fatalWarnings = settings.Xwarnfatal.value
     def logClasspath  = settings.Ylogcp.value
     def printLate     = settings.printLate.value
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index 2c47239a92..a051177a87 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -603,14 +603,28 @@ abstract class ClassfileParser {
     if ((sflags & PRIVATE) != 0L && !global.settings.XO.value) {
       in.skip(4); skipAttributes()
     } else {
-      val name = pool.getName(in.nextChar)
-      val info = pool.getType(in.nextChar)
-      val sym = getOwner(jflags)
-        .newValue(NoPosition, name).setFlag(sflags)
-      sym.setInfo(if ((jflags & JAVA_ACC_ENUM) == 0) info else ConstantType(Constant(sym)))
+      val name    = pool.getName(in.nextChar)
+      val info    = pool.getType(in.nextChar)
+      val sym     = getOwner(jflags).newValue(NoPosition, name).setFlag(sflags)
+      val isEnum  = (jflags & JAVA_ACC_ENUM) != 0
+
+      sym setInfo {
+        if (isEnum) ConstantType(Constant(sym))
+        else info
+      }
       setPrivateWithin(sym, jflags)
       parseAttributes(sym, info)
       getScope(jflags).enter(sym)
+
+      // sealed java enums (experimental)
+      if (isEnum && opt.experimental) {
+        // need to give singleton type
+        sym setInfo info.narrow
+        if (!sym.superClass.isSealed)
+          sym.superClass setFlag (SEALED | ABSTRACT)
+
+        sym.superClass addChild sym
+      }
     }
   }
 
diff --git a/test/files/neg/sealed-java-enums.check b/test/files/neg/sealed-java-enums.check
new file mode 100644
index 0000000000..9a4bd4241e
--- /dev/null
+++ b/test/files/neg/sealed-java-enums.check
@@ -0,0 +1,8 @@
+sealed-java-enums.scala:5: error: match is not exhaustive!
+missing combination        BLOCKED
+missing combination     TERMINATED
+missing combination  TIMED_WAITING
+
+  def f(state: State) = state match {
+                        ^
+one error found
diff --git a/test/files/neg/sealed-java-enums.flags b/test/files/neg/sealed-java-enums.flags
new file mode 100644
index 0000000000..e709c65918
--- /dev/null
+++ b/test/files/neg/sealed-java-enums.flags
@@ -0,0 +1 @@
+-Xexperimental -Xfatal-warnings
diff --git a/test/files/neg/sealed-java-enums.scala b/test/files/neg/sealed-java-enums.scala
new file mode 100644
index 0000000000..2daf93f308
--- /dev/null
+++ b/test/files/neg/sealed-java-enums.scala
@@ -0,0 +1,10 @@
+import java.lang.Thread.State
+import java.lang.Thread.State._
+
+object Test {
+  def f(state: State) = state match {
+    case NEW | WAITING  => true
+    case RUNNABLE       => false
+    // and I forget the rest
+  }
+}