From 2865d8bd45294ebadd5c640b7dbb24574a10420c Mon Sep 17 00:00:00 2001
From: Svyatoslav Scherbina <svyatoslav.scherbina@jetbrains.com>
Date: Mon, 28 Jun 2021 17:40:12 +0300
Subject: [PATCH] Deprecate Obj-C 'alloc' and 'allocWithZone:' methods in
 Kotlin

Using these methods in Kotlin is usually a mistake.
---
 .../kotlin/native/interop/gen/ObjCStubs.kt     | 18 ++++++++++++++++++
 .../kotlin/native/interop/gen/StubIr.kt        |  6 ++++++
 2 files changed, 24 insertions(+)

diff --git a/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/ObjCStubs.kt b/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/ObjCStubs.kt
index 668b1f8e5a1..f0a0570b26f 100644
--- a/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/ObjCStubs.kt
+++ b/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/ObjCStubs.kt
@@ -148,7 +148,22 @@ private class ObjCMethodStubBuilder(
     fun isDefaultConstructor(): Boolean =
             method.isInit && method.parameters.isEmpty()
 
+    private fun deprecateObjCAlloc() {
+        // Motivation: 'alloc' and 'allocWithZone:' Obj-C methods were never intended to be directly accessible
+        // in Kotlin.
+        // Using these methods in Kotlin is error-prone: init methods are not accessible,
+        // so a call to alloc method is likely not followed by a call to an init method,
+        // which is usually a mistake.
+        // Swift also doesn't allow calling Obj-C alloc methods.
+        // Removing them gracefully, via the deprecation cycle:
+        if (method.isAlloc()) {
+            annotations += AnnotationStub.Deprecated.deprecatedObjCAlloc
+        }
+    }
+
     override fun build(): List<FunctionalStub> {
+        deprecateObjCAlloc()
+
         val replacement = if (method.isInit) {
             val parameters = method.getKotlinParameters(context, forConstructorOrFactory = true)
             when (container) {
@@ -243,6 +258,9 @@ private fun deprecatedInit(className: String, initParameterNames: List<String>,
     return AnnotationStub.Deprecated("Use $replacementKind instead", replaceWith, DeprecationLevel.ERROR)
 }
 
+private fun ObjCMethod.isAlloc(): Boolean =
+        this.isClass && (this.selector == "alloc" || this.selector == "allocWithZone:")
+
 internal val ObjCMethod.kotlinName: String
     get() {
         val candidate = selector.split(":").first()
diff --git a/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/StubIr.kt b/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/StubIr.kt
index 3d5af9d9d6e..a871c7c5e45 100644
--- a/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/StubIr.kt
+++ b/kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/StubIr.kt
@@ -238,6 +238,12 @@ sealed class AnnotationStub(val classifier: Classifier) {
                     "",
                     DeprecationLevel.WARNING
             )
+
+            val deprecatedObjCAlloc = Deprecated(
+                    "Use constructor or factory method instead",
+                    "",
+                    DeprecationLevel.WARNING
+            )
         }
     }