prevent serialization of allocating inits for actors

A public designated initializer of a class would have its allocating
entry-point serialized in the module, meaning with `-O` that entry-point
can get inlined into programs linking against that module. Once that
entry-point is inlined, the program will _require_ that it remain non-delegating,
because it will depend on the 2nd entry-point (for actual initializing) to be in the
library.

As a result of this change, public initializers of an actor should be resilient in a
library, whether their underlying implementation is delegating or not.

Author: kavon

lib/SIL/IR/SILDeclRef.cpp

@@ -669,13 +669,14 @@ IsSerialized_t SILDeclRef::isSerialized() const {
     return IsSerialized;
 
   // The allocating entry point for designated initializers are serialized
-  // if the class is @usableFromInline or public.
+  // if the class is @usableFromInline or public. Actors are excluded because
+  // whether the init is designated is not clearly reflected in the source code.
   if (kind == SILDeclRef::Kind::Allocator) {
     auto *ctor = cast<ConstructorDecl>(d);
-    if (ctor->isDesignatedInit() &&
-        ctor->getDeclContext()->getSelfClassDecl()) {
-      if (!ctor->hasClangNode())
-        return IsSerialized;
+    if (auto classDecl = ctor->getDeclContext()->getSelfClassDecl()) {
+      if (!classDecl->isAnyActor() && ctor->isDesignatedInit())
+        if (!ctor->hasClangNode())
+          return IsSerialized;
     }
   }
 

test/SILGen/inlinable_attribute.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-silgen -module-name inlinable_attribute -emit-verbose-sil -warnings-as-errors %s | %FileCheck %s
+// RUN: %target-swift-emit-silgen -module-name inlinable_attribute -emit-verbose-sil -warnings-as-errors -disable-availability-checking %s | %FileCheck %s
 
 // CHECK-LABEL: sil [serialized] [ossa] @$s19inlinable_attribute15fragileFunctionyyF : $@convention(thin) () -> ()
 @inlinable public func fragileFunction() {
@@ -37,6 +37,32 @@ public class MyCls {
   }
 }
 
+public actor MyAct {
+  // CHECK-LABEL: sil [serialized] [ossa] @$s19inlinable_attribute5MyActCfD : $@convention(method) (@owned MyAct) -> ()
+  @inlinable deinit {}
+
+  /// whether delegating or not, the initializers for an actor are not serialized unless marked inlinable.
+
+  // CHECK-LABEL: sil [exact_self_class] [ossa] @$s19inlinable_attribute5MyActC14designatedInitACyt_tcfC : $@convention(method) (@thick MyAct.Type) -> @owned MyAct
+  // CHECK-LABEL: sil [ossa] @$s19inlinable_attribute5MyActC14designatedInitACyt_tcfc : $@convention(method) (@owned MyAct) -> @owned MyAct
+  public init(designatedInit: ()) {}
+
+  // CHECK-LABEL: sil [ossa] @$s19inlinable_attribute5MyActC15convenienceInitACyt_tcfC : $@convention(method) (@thick MyAct.Type) -> @owned MyAct
+  public init(convenienceInit: ()) {
+    self.init(designatedInit: ())
+  }
+
+
+  // CHECK-LABEL: sil [serialized] [exact_self_class] [ossa] @$s19inlinable_attribute5MyActC0A14DesignatedInitACyt_tcfC : $@convention(method) (@thick MyAct.Type) -> @owned MyAct
+  // CHECK-LABEL: sil [serialized] [ossa] @$s19inlinable_attribute5MyActC0A14DesignatedInitACyt_tcfc : $@convention(method) (@owned MyAct) -> @owned MyAct
+  @inlinable public init(inlinableDesignatedInit: ()) {}
+
+  // CHECK-LABEL: sil [serialized] [ossa] @$s19inlinable_attribute5MyActC0A15ConvenienceInitACyt_tcfC : $@convention(method) (@thick MyAct.Type) -> @owned MyAct
+  @inlinable public init(inlinableConvenienceInit: ()) {
+    self.init(designatedInit: ())
+  }
+}
+
 // Make sure enum case constructors for public and versioned enums are
 // [serialized].
 @usableFromInline enum MyEnum {