From be3df1782b689858f15a9a1dd518b65794e91e09 Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Fri, 6 Mar 2020 08:54:07 +0000
Subject: [PATCH] Silence outer pointer warnings in class-based REPL

Case classes, such as final case classes nested within other classes,
lose their outer pointer which makes their equality lie (scala/bug#4440):

    scala> class Outer { final case class Inner(n: Int) }
    warning: there was one unchecked warning; for details, enable `:setting -unchecked' or `:replay -unchecked'
    defined class Outer

    scala> val o1, o2 = new Outer
    o1: Outer = Outer@627bcd7e
    o2: Outer = Outer@70543cae

    scala> new o1.Inner(1) == new o2.Inner(1)
    res0: Boolean = true

vs

    scala> class Outer { case class Inner(n: Int) }
    defined class Outer

    scala> val o1, o2 = new Outer
    o1: Outer = Outer@77ba583
    o2: Outer = Outer@5613247e

    scala> new o1.Inner(1) == new o2.Inner(1)
    res0: Boolean = false

This isn't a problem in the REPL even with its class-based wrappers as
there is only ever 1 instance of (each) wrapper class.
---
 .../transform/patmat/MatchTreeMaking.scala    |  2 +-
 .../run/repl-class-based-outer-pointers.check | 14 ++++++++
 .../run/repl-class-based-outer-pointers.scala | 35 +++++++++++++++++++
 3 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 test/files/run/repl-class-based-outer-pointers.check
 create mode 100644 test/files/run/repl-class-based-outer-pointers.scala

diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
index 4a6731744dcd..15f3dba8247b 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
@@ -355,7 +355,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
           // this also includes methods and (possibly nested) objects inside of methods.
           def definedInStaticLocation(tp: Type): Boolean = {
             def isStatic(tp: Type): Boolean =
-              if (tp == NoType || tp.typeSymbol.isPackageClass || tp == NoPrefix) true
+              if (tp == NoType || tp.typeSymbol.isPackageClass || tp == NoPrefix || nme.isReplWrapperName(tp.typeSymbol.name)) true
               else if (tp.typeSymbol.isModuleClass) isStatic(tp.prefix)
               else false
             tp.typeSymbol.owner == tp.prefix.typeSymbol && isStatic(tp.prefix)
diff --git a/test/files/run/repl-class-based-outer-pointers.check b/test/files/run/repl-class-based-outer-pointers.check
new file mode 100644
index 000000000000..0e2fec8062c1
--- /dev/null
+++ b/test/files/run/repl-class-based-outer-pointers.check
@@ -0,0 +1,14 @@
+
+scala> sealed abstract class Value; object Value {
+  final case class Num(value: Double) extends Value
+  final case class Str(value: String) extends Value
+  final case class Bool(value: Boolean) extends Value
+}
+defined class Value
+defined object Value
+
+scala> class C { final case class Num(value: Double) } // here it should still warn
+warning: there was one unchecked warning; for details, enable `:setting -unchecked' or `:replay -unchecked'
+defined class C
+
+scala> :quit
diff --git a/test/files/run/repl-class-based-outer-pointers.scala b/test/files/run/repl-class-based-outer-pointers.scala
new file mode 100644
index 000000000000..58cbed80b4a5
--- /dev/null
+++ b/test/files/run/repl-class-based-outer-pointers.scala
@@ -0,0 +1,35 @@
+import scala.tools.nsc.Settings
+import scala.tools.partest.ReplTest
+
+object Test extends ReplTest {
+  override def transformSettings(s: Settings) = {
+    s.Yreplclassbased.value = true
+    s
+  }
+
+  def code = """
+    |sealed abstract class Value; object Value {
+    |  final case class Num(value: Double) extends Value
+    |  final case class Str(value: String) extends Value
+    |  final case class Bool(value: Boolean) extends Value
+    |}
+    |class C { final case class Num(value: Double) } // here it should still warn
+    |""".stripMargin // scala/bug#11902
+}
+
+/* was:
+
+scala> sealed abstract class Value; object Value {
+  final case class Num(value: Double) extends Value
+  final case class Str(value: String) extends Value
+  final case class Bool(value: Boolean) extends Value
+}
+warning: there were three unchecked warnings; for details, enable `:setting -unchecked' or `:replay -unchecked'
+defined class Value
+defined object Value
+
+scala> class C { final case class Num(value: Double) } // here it should still warn
+warning: there was one unchecked warning; for details, enable `:setting -unchecked' or `:replay -unchecked'
+defined class C
+
+ */