Merge pull request #944 from dotty-staging/fix-tailrec

Tailrec: fix compilation of IndexedSeqOptimized

Author: DarkDimius

src/dotty/tools/dotc/Compiler.scala

@@ -52,6 +52,7 @@ class Compiler {
       List(new PatternMatcher,
            new ExplicitOuter,
            new ExplicitSelf,
+           new CrossCastAnd,
            new Splitter),
       List(new VCInlineMethods,
            new SeqLiterals,

src/dotty/tools/dotc/transform/CrossCastAnd.scala

@@ -0,0 +1,30 @@
+package dotty.tools.dotc.transform
+
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Flags
+import dotty.tools.dotc.core.Types.{NoType, Type, AndType}
+import dotty.tools.dotc.transform.TreeTransforms._
+import tpd._
+
+import scala.collection.mutable.ListBuffer
+
+
+/**
+ * This transform makes sure that all private member selections from
+ * AndTypes are performed from the first component of AndType.
+ * This is needed for correctness of erasure. See `tests/run/PrivateAnd.scala`
+ */
+class CrossCastAnd extends MiniPhaseTransform { thisTransform =>
+
+  override def phaseName: String = "crossCast"
+
+  override def transformSelect(tree: tpd.Select)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
+
+    lazy val qtype = tree.qualifier.tpe.widen
+    val sym = tree.symbol
+    if (sym.is(Flags.Private) && qtype.typeSymbol != sym.owner)
+      cpy.Select(tree)(tree.qualifier.asInstance(AndType(qtype.baseTypeWithArgs(sym.owner), tree.qualifier.tpe)), tree.name)
+    else tree
+  }
+}

src/dotty/tools/dotc/transform/TailRec.scala

@@ -185,7 +185,7 @@ class TailRec extends MiniPhaseTransform with DenotTransformer with FullParamete
 
         val receiverIsSame = enclosingClass.typeRef.widenDealias =:= recvWiden
         val receiverIsSuper = (method.name eq sym) && enclosingClass.typeRef.widen <:< recvWiden
-        val receiverIsThis = recv.tpe =:= thisType
+        val receiverIsThis = recv.tpe =:= thisType || recv.tpe.widen =:= thisType
 
         val isRecursiveCall = (method eq sym)
 

tests/pos/ErasureAnd.scala

@@ -0,0 +1,11 @@
+import scala.annotation.tailrec
+trait A { self: B =>
+  @tailrec
+  private def foo(arg1: Int, arg2: Int): Int = {
+    def bar = this.foo(arg1, arg2)
+    foo(arg1, arg2)
+  }
+  def foo(arg: Int) = arg
+}
+
+class B extends A{}

tests/run/PrivateAnd.scala

@@ -0,0 +1,17 @@
+class A{
+  private def foo = 1
+  def callsFoo1(other: A & B): Int = other.foo
+  def callsFoo2(other: B & A): Int = other.foo
+}
+
+trait B {
+  def foo(i: Int) = i
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val a = new A with B
+    a.callsFoo1(a)
+    a.callsFoo2(a)	
+  }
+}