Shadow addSuppressed member with an extension

#KT-38777

libraries/stdlib/jdk7/src/kotlin/internal/jdk7/JDK7PlatformImplementations.kt

@@ -10,7 +10,8 @@ import kotlin.internal.PlatformImplementations
 
 internal open class JDK7PlatformImplementations : PlatformImplementations() {
 
-    override fun addSuppressed(cause: Throwable, exception: Throwable) = cause.addSuppressed(exception)
+    @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN")
+    override fun addSuppressed(cause: Throwable, exception: Throwable) = (cause as java.lang.Throwable).addSuppressed(exception)
 
     override fun getSuppressed(exception: Throwable): List<Throwable> = exception.suppressed.asList()
 }

libraries/stdlib/jvm/src/kotlin/util/Exceptions.kt

@@ -65,6 +65,7 @@ public actual fun Throwable.stackTraceToString(): String {
  * suppressed in order to deliver this exception.
  */
 @SinceKotlin("1.1")
+@kotlin.internal.HidesMembers
 public actual fun Throwable.addSuppressed(exception: Throwable) {
     if (this !== exception)
         IMPLEMENTATIONS.addSuppressed(this, exception)

libraries/stdlib/jvm/test/ExceptionJVMTest.kt

@@ -81,6 +81,11 @@ class ExceptionJVMTest {
         e1.addSuppressed(e2)
     }
 
+    @Test fun addSuppressedSelfDoesNotThrow() {
+        val e1 = Throwable()
+        e1.addSuppressed(e1) // should not throw
+    }
+
     @Test fun circularCauseStackTrace() {
         val e1 = Exception("cause")
         val e2 = Error("induced", e1)