Support new repeatable annotations in kotlin-reflect

- Unwrap Kotlin-repeatable annotations (with implicit container)
- Introduce `KAnnotatedElement.findAnnotations` to find instances of
  repeated annotations

 #KT-12794

compiler/testData/codegen/box/reflection/annotations/findAnnotation.kt

@@ -1,9 +1,12 @@
 // IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: JS_IR_ES6
 // IGNORE_BACKEND: JS, NATIVE
+// !USE_EXPERIMENTAL: kotlin.ExperimentalStdlibApi
 // WITH_REFLECT
 
 import kotlin.reflect.full.findAnnotation
+import kotlin.reflect.full.findAnnotations
+import kotlin.test.assertEquals
 import kotlin.test.assertNull
 
 annotation class Yes(val value: String)
@@ -19,5 +22,7 @@ fun box(): String {
     assertNull(Bar::class.findAnnotation<Yes>())
     assertNull(Bar::class.findAnnotation<No>())
 
+    assertEquals("OK", Foo::class.findAnnotations<Yes>().single().value)
+
     return Foo::class.findAnnotation<Yes>()?.value ?: "Fail: no annotation"
 }

compiler/testData/codegen/box/reflection/annotations/repeatable/javaAnnotation.kt

@@ -0,0 +1,44 @@
+// !LANGUAGE: +RepeatableAnnotations
+// !USE_EXPERIMENTAL: kotlin.ExperimentalStdlibApi
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FULL_JDK
+// WITH_REFLECT
+// FILE: box.kt
+
+import kotlin.reflect.full.findAnnotation
+import kotlin.reflect.full.findAnnotations
+import kotlin.reflect.full.hasAnnotation
+
+@A("O")
+@A("")
+@A("K")
+fun f() {}
+
+fun box(): String {
+    val element = ::f
+    if (element.hasAnnotation<A>()) return "Fail hasAnnotation $element"
+    val find = element.findAnnotation<A>()
+    if (find != null) return "Fail findAnnotation $element: $find"
+
+    val all = (element.annotations.single() as A.Container).value.asList()
+    val findAll = element.findAnnotations<A>()
+    if (all != findAll) throw AssertionError("Fail findAnnotations $element: $all != $findAll")
+
+    return all.fold("") { acc, it -> acc + it.value }
+}
+
+// FILE: A.java
+
+import java.lang.annotation.*;
+
+@Repeatable(A.Container.class)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface A {
+    String value();
+
+    @Retention(RetentionPolicy.RUNTIME)
+    public @interface Container {
+        A[] value();
+    }
+}

compiler/testData/codegen/box/reflection/annotations/repeatable/jvmRepeatableKotlinAnnotation.kt

@@ -0,0 +1,36 @@
+// !LANGUAGE: +RepeatableAnnotations
+// !USE_EXPERIMENTAL: kotlin.ExperimentalStdlibApi
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FULL_JDK
+// WITH_REFLECT
+
+// Android doesn't have @Repeatable, so findAnnotations can't unpack repeatable annotations.
+// IGNORE_BACKEND: ANDROID
+
+import kotlin.reflect.full.findAnnotation
+import kotlin.reflect.full.findAnnotations
+import kotlin.reflect.full.hasAnnotation
+
+@java.lang.annotation.Repeatable(A.Container::class)
+annotation class A(val value: String) {
+    annotation class Container(val value: Array<A>)
+}
+
+@A("O")
+@A("")
+@A("K")
+fun f() {}
+
+fun box(): String {
+    val element = ::f
+    if (element.hasAnnotation<A>()) return "Fail hasAnnotation $element"
+    val find = element.findAnnotation<A>()
+    if (find != null) return "Fail findAnnotation $element: $find"
+
+    val all = (element.annotations.single() as A.Container).value.asList()
+    val findAll = element.findAnnotations<A>()
+    if (all != findAll) throw AssertionError("Fail findAnnotations $element: $all != $findAll")
+
+    return all.fold("") { acc, it -> acc + it.value }
+}

compiler/testData/codegen/box/reflection/annotations/repeatable/kotlinAnnotation.kt

@@ -0,0 +1,54 @@
+// !LANGUAGE: +RepeatableAnnotations
+// !USE_EXPERIMENTAL: kotlin.ExperimentalStdlibApi
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FULL_JDK
+// WITH_REFLECT
+
+// Test failed to run to completion. Reason: 'Instrumentation run failed due to 'Native crash''. Check device logcat for details
+// IGNORE_BACKEND: ANDROID
+
+import kotlin.annotation.AnnotationTarget.*
+import kotlin.reflect.KAnnotatedElement
+import kotlin.reflect.full.findAnnotation
+import kotlin.reflect.full.findAnnotations
+import kotlin.reflect.full.hasAnnotation
+
+fun check(element: KAnnotatedElement) {
+    if (!element.hasAnnotation<A>()) throw AssertionError("Fail hasAnnotation $element")
+
+    val find = element.findAnnotation<A>()
+    if (find == null || find.value != "O") throw AssertionError("Fail findAnnotation $element: $find")
+
+    val all = element.annotations
+    val findAll = element.findAnnotations<A>()
+    if (all != findAll) throw AssertionError("Fail findAnnotations $element: $all != $findAll")
+
+    if (all.any { it !is A })
+        throw AssertionError("Fail 1 $element: $all")
+    if (all.fold("") { acc, it -> acc + (it as A).value } != "OK")
+        throw AssertionError("Fail 2 $element: $all")
+}
+
+@Repeatable
+@Target(CLASS, FUNCTION, PROPERTY, TYPE)
+annotation class A(val value: String)
+
+@A("O") @A("") @A("K")
+fun f() {}
+
+@A("O") @A("") @A("") @A("K")
+var p = 1
+
+@A("O") @A("K")
+class Z
+
+fun g(): @A("O") @A("K") @A("") Unit {}
+
+fun box(): String {
+    check(::f)
+    check(::p)
+    check(Z::class)
+    check(::g.returnType)
+    return "OK"
+}

compiler/testData/codegen/box/reflection/annotations/repeatable/nonRepeatedAnnotationWithItsContainer.kt

@@ -0,0 +1,44 @@
+// !LANGUAGE: +RepeatableAnnotations
+// !USE_EXPERIMENTAL: kotlin.ExperimentalStdlibApi
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FULL_JDK
+// WITH_REFLECT
+
+// Android doesn't have @Repeatable.
+// IGNORE_BACKEND: ANDROID
+
+package test
+
+import kotlin.test.assertEquals
+import kotlin.reflect.full.*
+
+@java.lang.annotation.Repeatable(As::class)
+annotation class A(val value: Int)
+
+annotation class As(val value: Array<A>)
+
+@A(1)
+@As([A(2), A(3)])
+class Z
+
+@As([A(1), A(2)])
+@A(3)
+class ZZ
+
+// JDK 9+ uses {} for array arguments instead of [], JDK 15+ doesn't render "value="
+fun Any?.render(): String =
+    toString().replace("value=", "").replace("{", "[").replace("}", "]")
+
+// Explicit container is not unwrapped.
+fun box(): String {
+    assertEquals("[@test.A(1), @test.As([@test.A(2), @test.A(3)])]", Z::class.annotations.render())
+    assertEquals("[@test.A(1)]", Z::class.findAnnotations<A>().render())
+    assertEquals("@test.A(1)", Z::class.findAnnotation<A>().render())
+
+    assertEquals("[@test.As([@test.A(1), @test.A(2)]), @test.A(3)]", ZZ::class.annotations.render())
+    assertEquals("[@test.A(3)]", ZZ::class.findAnnotations<A>().render())
+    assertEquals("@test.A(3)", ZZ::class.findAnnotation<A>().render())
+
+    return "OK"
+}