From 8448beb2ad6346d1d04a1feedb3de4d77f61024d Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Wed, 24 Apr 2013 12:22:44 -0700
Subject: SI-6943 warn on value class miscomparison.

There's a very dangerous situation running around when you
combine universal equality with value classes:

  // All over your code
  val x = "abc"
  if (x == "abc") ...

  // Hey let's make x a value class
  val x = new ValueClass("abc")
  // Uh-oh

There was until now no warning when comparing a value class
with something else. Now there is.
---
 test/files/neg/t5663-badwarneq.scala | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'test/files/neg/t5663-badwarneq.scala')

diff --git a/test/files/neg/t5663-badwarneq.scala b/test/files/neg/t5663-badwarneq.scala
index 56ec389c03..3c0376914e 100644
--- a/test/files/neg/t5663-badwarneq.scala
+++ b/test/files/neg/t5663-badwarneq.scala
@@ -17,6 +17,11 @@ class SimpleParent
 case class Simple() extends SimpleParent
 case object SimpleSibling extends SimpleParent
 
+// value classes
+final class ValueClass1(val value: Int) extends AnyVal
+final class ValueClass2[T](val value: T) extends AnyVal
+final case class ValueClass3(val value: Int) extends AnyVal
+
 /* It's not possible to run partest without -deprecation.
  * Since detecting the warnings requires a neg test with
  * -Xfatal-warnings, and deprecation terminates the compile,
@@ -63,6 +68,19 @@ object Test {
 
     println(new Simple() == SimpleSibling) // like Some(1) == None, but needn't be final case
 
+    println(new ValueClass1(5) == new ValueClass1(5)) // ok
+    println(new ValueClass1(5) == 5) // bad
+    println(new ValueClass1(5) == (5: Any)) // ok, have to let it through
+    println(5 == new ValueClass1(5)) // bad
+    println((5: Any) == new ValueClass1(5) == (5: Any)) // ok
+
+    println(new ValueClass2("abc") == new ValueClass2("abc")) // ok
+    println(new ValueClass2("abc") == "abc") // bad
+    println(new ValueClass2(5) == new ValueClass1(5)) // bad - different value classes
+    println(ValueClass3(5) == new ValueClass3(5)) // ok
+    println(ValueClass3(5) == new ValueClass2(5)) // bad
+    println(ValueClass3(5) == 5) // bad
+
     /*
     val mine = new MyThing
     val some = new SomeThing
-- 
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