From 05cf8f60e3010c09539e8f1d7c7860eaeeb9ff0b Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Fri, 20 Apr 2018 18:37:04 +0200
Subject: [PATCH] Fix #4323: allow narrowing of class type parameters in
 pattern match

---
 compiler/src/dotty/tools/dotc/config/Settings.scala |  2 +-
 compiler/src/dotty/tools/dotc/typer/Typer.scala     |  2 +-
 tests/pos/i4323.scala                               |  9 +++++++++
 tests/pos/i4323b.scala                              | 13 +++++++++++++
 tests/pos/i4323c.scala                              | 11 +++++++++++
 5 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 tests/pos/i4323.scala
 create mode 100644 tests/pos/i4323b.scala
 create mode 100644 tests/pos/i4323c.scala

diff --git a/compiler/src/dotty/tools/dotc/config/Settings.scala b/compiler/src/dotty/tools/dotc/config/Settings.scala
index 6343341b29f4..6240cfc3ba48 100644
--- a/compiler/src/dotty/tools/dotc/config/Settings.scala
+++ b/compiler/src/dotty/tools/dotc/config/Settings.scala
@@ -137,7 +137,7 @@ object Settings {
           else update((argRest split ",").toList, args)
         case (StringTag, _) if choices.nonEmpty =>
           if (argRest.isEmpty) missingArg
-          else if (!choices.contains(argRest))
+          else if (!choices.contains(argRest.asInstanceOf[T]))
             fail(s"$arg is not a valid choice for $name", args)
           else update(argRest, args)
         case (StringTag, arg :: args) if name == "-d" =>
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index fcba55cf99d4..038ea32f20e7 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -984,7 +984,7 @@ class Typer extends Namer
       val accu = new TypeAccumulator[Set[Symbol]] {
         def apply(tsyms: Set[Symbol], t: Type): Set[Symbol] = {
           val tsyms1 = t match {
-            case tr: TypeRef if (tr.symbol is TypeParam) && tr.symbol.owner.isTerm && variance == 0 =>
+            case tr: TypeRef if (tr.symbol is TypeParam) && variance == 0 =>
               tsyms + tr.symbol
             case _ =>
               tsyms
diff --git a/tests/pos/i4323.scala b/tests/pos/i4323.scala
new file mode 100644
index 000000000000..4ef22d44511e
--- /dev/null
+++ b/tests/pos/i4323.scala
@@ -0,0 +1,9 @@
+enum Expr[T] {
+  case IExpr(value: Int) extends Expr[Int]
+  case BExpr(value: Boolean) extends Expr[Boolean]
+
+  def join(other: Expr[T]): Expr[T] = (this, other) match {
+    case (IExpr(i1), IExpr(i2)) => IExpr(i1 + i2)
+    case (BExpr(b1), BExpr(b2)) => BExpr(b1 & b2)
+  }
+}
diff --git a/tests/pos/i4323b.scala b/tests/pos/i4323b.scala
new file mode 100644
index 000000000000..7d5c72b8522e
--- /dev/null
+++ b/tests/pos/i4323b.scala
@@ -0,0 +1,13 @@
+sealed trait Expr[T] {
+  import Expr._
+
+   def join(other: Expr[T]): Expr[T] = (this, other) match {
+     case (IExpr(i1), IExpr(i2)) => IExpr(i1 + i2)
+     case (BExpr(b1), BExpr(b2)) => BExpr(b1 & b2)
+   }
+}
+
+object Expr {
+  case class IExpr(value: Int) extends Expr[Int]
+  case class BExpr(value: Boolean) extends Expr[Boolean]
+}
diff --git a/tests/pos/i4323c.scala b/tests/pos/i4323c.scala
new file mode 100644
index 000000000000..eaf38d48e325
--- /dev/null
+++ b/tests/pos/i4323c.scala
@@ -0,0 +1,11 @@
+sealed trait Expr[T] { outer =>
+  class Inner {
+    def join(other: Expr[T]): Expr[T] = (outer, other) match {
+      case (IExpr(i1), IExpr(i2)) => IExpr(i1 + i2)
+      case (BExpr(b1), BExpr(b2)) => BExpr(b1 & b2)
+    }
+  }
+}
+
+case class IExpr(value: Int) extends Expr[Int]
+case class BExpr(value: Boolean) extends Expr[Boolean]