Make Throwable.addSuppressed extension work without kotlin-stdlib-jdk7*

*given that it runs on JDK7 and higher. The addSuppressed member
is called with reflection when it's available.
kotlin-stdlib-jdk7 extension still overrides that and calls
addSuppressed member statically as before.

#KT-30560 Fixed

libraries/stdlib/jdk7/build.gradle

@@ -12,11 +12,6 @@ pill {
     importAsLibrary = true
 }
 
-dependencies {
-    compile project(':kotlin-stdlib')
-    testCompile project(':kotlin-test:kotlin-test-junit')
-}
-
 sourceSets {
     main {
         kotlin {
@@ -33,6 +28,11 @@ sourceSets {
             }
         }
     }
+    noJdk7Test {
+        kotlin {
+            srcDir 'testNoJdk7'
+        }
+    }
     java9 {
         java {
             srcDir 'java9'
@@ -40,6 +40,15 @@ sourceSets {
     }
 }
 
+configurations {
+    noJdk7TestCompile.extendsFrom(testCompile)
+}
+
+dependencies {
+    compile project(':kotlin-stdlib')
+    testCompile project(':kotlin-test:kotlin-test-junit')
+}
+
 jar {
     manifestAttributes(manifest, project, 'Main' /*true*/)
     // TODO: enable as soon as this doesn't cause D8/DX to crash
@@ -106,4 +115,15 @@ task testJdk6Tests(type: Test) {
     }
 }
 
-check.dependsOn testJdk6Tests
+task testNoJdk7(type: Test, dependsOn: noJdk7TestClasses) {
+    group = "verification"
+
+    executable = "$JDK_17/bin/java"
+
+    testClassesDirs = sourceSets.noJdk7Test.output.classesDirs
+    classpath = sourceSets.noJdk7Test.runtimeClasspath
+}
+
+
+check.dependsOn testJdk6Tests, testNoJdk7
+

libraries/stdlib/jdk7/testNoJdk7/ExceptionTest.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package test.exceptions
+
+import kotlin.addSuppressed as addSuppressedExtension
+import kotlin.test.*
+
+class ExceptionTest {
+
+    @Test
+    fun addSuppressedWorksWithoutJdk7Extensions() {
+        val e1 = Throwable()
+        val e2 = Exception("Suppressed")
+
+        e1.addSuppressedExtension(e2)
+
+        assertSame(e2, e1.suppressed.singleOrNull())
+    }
+
+}

libraries/stdlib/jvm/src/kotlin/internal/PlatformImplementations.kt

@@ -5,14 +5,24 @@
 
 package kotlin.internal
 
+import java.lang.reflect.Method
 import java.util.regex.MatchResult
 import kotlin.random.FallbackThreadLocalRandom
 import kotlin.random.Random
 
 internal open class PlatformImplementations {
 
+    private object ReflectAddSuppressedMethod {
+        @JvmField
+        public val method: Method? = Throwable::class.java.let { throwableClass ->
+            throwableClass.methods.find {
+                it.name == "addSuppressed" && it.parameterTypes.singleOrNull() == throwableClass
+            }
+        }
+    }
+
     public open fun addSuppressed(cause: Throwable, exception: Throwable) {
-        // do nothing
+        ReflectAddSuppressedMethod.method?.invoke(cause, exception)
     }
 
     public open fun getMatchResultNamedGroup(matchResult: MatchResult, name: String): MatchGroup? {

libraries/stdlib/jvm/test/ExceptionJVMTest.kt

@@ -65,4 +65,11 @@ class ExceptionJVMTest {
         exception.stackTrace = stackTrace
         assertArrayNotSameButEquals(stackTrace, exception.stackTrace)
     }
+
+    @Test fun addSuppressedDoesNotThrow() {
+        val e1 = Throwable()
+        val e2 = Exception("Suppressed")
+
+        e1.addSuppressed(e2)
+    }
 }