Fixes for #3126.

null, and thrown MatchErrors don't NPE trying to stringify null. No
review.

4 files changed, 19 insertions, 7 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeDSL.scala b/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
index a788015262..fd13958053 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeDSL.scala
@@ -88,6 +88,8 @@ trait TreeDSL {
       def ANY_>=  (other: Tree)     = fn(target, nme.GE, other)
       def ANY_<=  (other: Tree)     = fn(target, nme.LE, other)
       def OBJ_!=  (other: Tree)     = fn(target, Object_ne, other)
+      def OBJ_EQ  (other: Tree)     = fn(target, nme.eq, other)
+      def OBJ_NE  (other: Tree)     = fn(target, nme.ne, other)
 
       def INT_|   (other: Tree)     = fn(target, getMember(IntClass, nme.OR), other)
       def INT_&   (other: Tree)     = fn(target, getMember(IntClass, nme.AND), other)
@@ -187,10 +189,11 @@ trait TreeDSL {
     }
 
     /** Top level accessible. */
-    def THROW(sym: Symbol, msg: Tree = null) = {
-      val arg: List[Tree] = if (msg == null) Nil else List(msg.TOSTRING())
-      Throw(New(TypeTree(sym.tpe), List(arg)))
-    }
+    def MATCHERROR(arg: Tree) = Throw(New(TypeTree(MatchErrorClass.tpe), List(List(arg))))
+    /** !!! should generalize null guard from match error here. */
+    def THROW(sym: Symbol): Throw = Throw(New(TypeTree(sym.tpe), List(Nil)))
+    def THROW(sym: Symbol, msg: Tree): Throw = Throw(New(TypeTree(sym.tpe), List(List(msg.TOSTRING()))))
+
     def NEW(tpe: Tree, args: Tree*)   = New(tpe, List(args.toList))
     def NEW(sym: Symbol, args: Tree*) =
       if (args.isEmpty) New(TypeTree(sym.tpe))
diff --git a/src/compiler/scala/tools/nsc/matching/TransMatcher.scala b/src/compiler/scala/tools/nsc/matching/TransMatcher.scala
index 5333734afa..be455b00b0 100644
--- a/src/compiler/scala/tools/nsc/matching/TransMatcher.scala
+++ b/src/compiler/scala/tools/nsc/matching/TransMatcher.scala
@@ -44,7 +44,7 @@ trait TransMatcher extends ast.TreeDSL {
   {
     import context._
 
-    def matchError(obj: Tree) = atPos(selector.pos)(THROW(MatchErrorClass, obj))
+    def matchError(obj: Tree) = atPos(selector.pos)(MATCHERROR(obj))
     def caseIsOk(c: CaseDef)  = cond(c.pat) { case _: Apply | Ident(nme.WILDCARD) => true }
     def rootTypes             = selector.tpe.typeArgs
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
index 3898e46c0b..5b3ca89e84 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
@@ -171,10 +171,10 @@ trait Unapplies extends ast.TreeDSL
       case _                                            => nme.unapply
     }
     val cparams   = List(ValDef(Modifiers(PARAM | SYNTHETIC), paramName, classType(cdef, tparams), EmptyTree))
+    val body      = nullSafe({ case Ident(x) => caseClassUnapplyReturnValue(x, cdef.symbol) }, MATCHERROR(NULL))(Ident(paramName))
 
     atPos(cdef.pos.focus)(
-      DefDef(caseMods, method, tparams, List(cparams), TypeTree(),
-        caseClassUnapplyReturnValue(paramName, cdef.symbol))
+      DefDef(caseMods, method, tparams, List(cparams), TypeTree(), body)
     )
   }
 
diff --git a/test/files/run/bug3126.scala b/test/files/run/bug3126.scala
new file mode 100644
index 0000000000..36322bf896
--- /dev/null
+++ b/test/files/run/bug3126.scala
@@ -0,0 +1,9 @@
+object Test {
+  case class C(x: Int)
+  val v: Some[Int] = null
+
+  def main(args: Array[String]): Unit = {
+    try C.unapply(null) catch { case _: MatchError => }
+    try v match { case Some(1) => } catch { case _: MatchError => }
+  }
+}