Fix for SI-5648.

More care in warning about bad comparisons.

4 files changed, 24 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 68a722aab4..806ee480f0 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1053,10 +1053,17 @@ abstract class RefChecks extends InfoTransform with reflect.internal.transform.R
         /** Symbols which limit the warnings we can issue since they may be value types */
         val isMaybeValue = Set(AnyClass, AnyRefClass, AnyValClass, ObjectClass, ComparableClass, JavaSerializableClass)
 
-        // Whether def equals(other: Any) is overridden or synthetic
+        // Whether def equals(other: Any) has known behavior: it is the default
+        // inherited from java.lang.Object, or it is a synthetically generated
+        // case equals.  TODO - more cases are warnable if the target is a synthetic
+        // equals.
         def isUsingWarnableEquals = {
           val m = receiver.info.member(nme.equals_)
-          (m == Object_equals) || (m == Any_equals) || (m.isSynthetic && m.owner.isCase)
+          def n = actual.info.member(nme.equals_)
+          (   (m == Object_equals)
+           || (m == Any_equals)
+           || (m.isSynthetic && m.owner.isCase && !n.owner.isCase)
+          )
         }
         // Whether this == or != is one of those defined in Any/AnyRef or an overload from elsewhere.
         def isUsingDefaultScalaOp = {
diff --git a/test/files/run/t5648.check b/test/files/run/t5648.check
new file mode 100644
index 0000000000..1140ff52e2
--- /dev/null
+++ b/test/files/run/t5648.check
@@ -0,0 +1,4 @@
+true
+true
+true
+true
diff --git a/test/files/run/t5648.flags b/test/files/run/t5648.flags
new file mode 100644
index 0000000000..e8fb65d50c
--- /dev/null
+++ b/test/files/run/t5648.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
\ No newline at end of file
diff --git a/test/files/run/t5648.scala b/test/files/run/t5648.scala
new file mode 100644
index 0000000000..c5cea9e1cb
--- /dev/null
+++ b/test/files/run/t5648.scala
@@ -0,0 +1,10 @@
+case class C(val s: Int*)
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println(new C(1, 3, 7) == new C(1, 3, 7))
+    println(new C(1, 3, 7) == C(1, 3, 7))
+    println(C(1, 3, 7) == new C(1, 3, 7))
+    println(C(1, 3, 7) == C(1, 3, 7))
+  }
+}