Fix #4557: Handle untpd.New with dealiased type

Author: Medowhill

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -311,11 +311,10 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     val (tycon, targs) = tpt match {
       case AppliedTypeTree(tycon, targs) =>
         (tycon, targs)
-      case TypedSplice(AppliedTypeTree(tycon, targs)) =>
-        (TypedSplice(tycon), targs map (TypedSplice(_)))
       case TypedSplice(tpt1: tpd.Tree) =>
-        val tycon = tpt1.tpe.typeConstructor
-        val argTypes = tpt1.tpe.argTypesLo
+        val tp = tpt1.tpe.dealias
+        val tycon = tp.typeConstructor
+        val argTypes = tp.argTypesLo
         def wrap(tpe: Type) = TypeTree(tpe) withPos tpt.pos
         (wrap(tycon), argTypes map wrap)
       case _ =>

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -516,7 +516,8 @@ class Typer extends Namer
           case TypeApplications.EtaExpansion(tycon) => tpt1 = tpt1.withType(tycon)
           case _ =>
         }
-        checkClassType(tpt1.tpe, tpt1.pos, traitReq = false, stablePrefixReq = true)
+        if (checkClassType(tpt1.tpe, tpt1.pos, traitReq = false, stablePrefixReq = true) eq defn.ObjectType)
+          tpt1 = TypeTree(defn.ObjectType).withPos(tpt1.pos)
 
         tpt1 match {
           case AppliedTypeTree(_, targs) =>

tests/neg/i4557.scala

@@ -0,0 +1,19 @@
+class C0[A]
+class C1[A, B]
+
+object O {
+  type T0 = C0
+  type T1 = C0[String, Int] // error
+  type T2[A] = C0[A, Int] // error
+
+  type S0 = C1
+  type S1 = C1[Int] // error
+
+  class D0 extends T0 // error
+  class D1 extends T0[Int]
+  class D2 extends T0[String, Int] // error
+
+  class E0 extends S0 // error
+  class E1 extends S0[Int] // error
+  class E2 extends S0[String, Int]
+}

tests/neg/i4557a.scala

@@ -0,0 +1,6 @@
+class A[X]
+
+object T {
+  type Foo[X, Y] = [Z] => A[X]
+  class B extends Foo[Int, Int] // error
+}

tests/pos/i2104b.decompiled

@@ -31,7 +31,7 @@ case class Pair[A, B](_1: A, _2: B) {
       throw new java.lang.IndexOutOfBoundsException(n.toString())
   }
 }
-object Pair extends scala.AnyRef()
+object Pair
 /** Decompiled from out/posTestFromTasty/pos/i2104b/Test.class */
 object Test {
   def main(args: scala.Array[scala.Predef.String]): scala.Unit = {

tests/pos/i4557.scala

@@ -0,0 +1,6 @@
+class Parser[T, Elem]
+
+object Test {
+  type P[T] = Parser[T, Char]
+  class CustomParser extends P[Unit]
+}

tests/pos/i4557a.scala

@@ -0,0 +1,6 @@
+class A[X]
+object O {
+  type T[X, Y] = A[X]
+  type S[X, Y] = T[X, Y]
+  class B extends S[Int, Int]
+}

tests/pos/simpleCaseClass-3.decompiled

@@ -22,4 +22,4 @@ case class A[T](x: T) {
       throw new java.lang.IndexOutOfBoundsException(n.toString())
   }
 }
-object A extends scala.AnyRef()
+object A

tests/run/i4557.check

@@ -0,0 +1,28 @@
+c0
+c0
+c1
+0
+c1
+1
+c1
+2
+c1
+3
+c2
+0
+a
+c2
+1
+b
+c2
+2
+c
+c2
+3
+d
+c2
+4
+e
+c2
+5
+f

tests/run/i4557.scala

@@ -0,0 +1,71 @@
+trait F {
+  def f: Unit
+}
+
+abstract class C0 extends F {
+  def f = println("c0")
+}
+
+abstract class C1[A](val a: A) extends F {
+  def f = {
+    println("c1")
+    println(a)
+  }
+}
+
+abstract class C2[A, B](val a: A, val b: B) extends F {
+  def f = {
+    println("c2")
+    println(a)
+    println(b)
+  }
+}
+
+object Test {
+  type T0 = C0
+  class DC0 extends C0
+  class DT0 extends T0
+
+  type T1[T] = C1[T]
+  class DC1 extends C1[Int](0)
+  class DT1 extends T1[Int](1)
+
+  type T11 = C1[Int]
+  class DT11 extends T11(2)
+
+  type T12 = C1
+  class DT12 extends T12[Int](3)
+
+  type T2[T, S] = C2[T, S]
+  class DC2 extends C2[Int, String](0, "a")
+  class DT2 extends T2[Int, String](1, "b")
+
+  type T21[T] = C2[T, String]
+  class DT21 extends T21[Int](2, "c")
+
+  type T22 = C2[Int, String]
+  class DT22 extends T22(3, "d")
+
+  type T23[T, S] = T2[T, S]
+  class DT23 extends T23(4, "e")
+
+  type T24 = C2
+  class DT24 extends T24[Int, String](5, "f")
+
+  def main(args: Array[String]) = {
+    List(
+      new DC0,
+      new DT0,
+      new DC1,
+      new DT1,
+      new DT11,
+      new DT12,
+      new DC2,
+      new DT2,
+      new DT21,
+      new DT22,
+      new DT23,
+      new DT24
+    ).foreach(_.f)
+  }
+}

tests/run/i4557a.check

@@ -0,0 +1,4 @@
+1
+a
+2
+b

tests/run/i4557a.scala

@@ -0,0 +1,24 @@
+abstract class C0[X, Y, Z, W](x: X, y: Y, z: Z, w: W) {
+  def f: Unit = {
+    println(x)
+    println(y)
+    println(z)
+    println(w)
+  }
+}
+
+object Test {
+  type T0[X, Y, Z, A, B, C] = C0[X, Y, Z, A]
+  type T1[A, B, C, D] = T0[A, B, C, D, Nothing, Any]
+  type T2[E, F] = T1[E, F, E, F]
+  type T3[X, Y, Z] = T2[X, Z]
+  type T4[X, Y, Z, W] = T3[X, W, Y]
+  type T5[A, B] = T4[A, B, (Int, Int), Unit]
+  type T6 = T5[Int, String]
+
+  class D extends T6(1, "a", 2, "b")
+
+  def main(args: Array[String]) = {
+    (new D).f
+  }
+}

tests/run/valueclasses-pavlov.decompiled

@@ -8,7 +8,7 @@ final class Box1(val value: scala.Predef.String) extends scala.AnyVal() {
       false
   }
 }
-object Box1 extends scala.AnyRef()
+object Box1
 /** Decompiled from out/runTestFromTasty/run/valueclasses-pavlov/Box2.class */
 final class Box2(val value: scala.Predef.String) extends scala.AnyVal() with Foo {
   def box1(x: Box1): scala.Predef.String = "box1: ok"
@@ -21,7 +21,7 @@ final class Box2(val value: scala.Predef.String) extends scala.AnyVal() with Foo
       false
   }
 }
-object Box2 extends scala.AnyRef()
+object Box2
 /** Decompiled from out/runTestFromTasty/run/valueclasses-pavlov/C.class */
 class C(x: scala.Predef.String) {
   def this() = {