[4.2] IRGen: Fix multi-payload enum lowering

When we have a private resilient enum that is resilient because one of
its payloads is resilient but we have disabled resilience in the
context of lowering the enum as a class member (sigh), we must consider
it's payload's layout enum in the minimal domain (ignore the private
visibility) because we don't truly know the layout.

* Scope: Private enums that contain a resilient payload and are used as
a stored property inside of a class will cause crashes
* Risk: Low
* Reviewed by: Slava
* Testing: CI test cases added
rdar://41308521

Author: aschwaighofer

lib/IRGen/GenDecl.cpp

@@ -4115,6 +4115,9 @@ IRGenModule::getResilienceExpansionForAccess(NominalTypeDecl *decl) {
 // layout. Calling isResilient() with this scope will always return false.
 ResilienceExpansion
 IRGenModule::getResilienceExpansionForLayout(NominalTypeDecl *decl) {
+  if (Types.isCompletelyFragile())
+    return ResilienceExpansion::Minimal;
+
   if (isResilient(decl, ResilienceExpansion::Minimal))
     return ResilienceExpansion::Maximal;
 

test/IRGen/enum_resilience_objc.swift

@@ -0,0 +1,25 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -enable-resilience -emit-module-path=%t/resilient_struct.swiftmodule -module-name=resilient_struct %S/../Inputs/resilient_struct.swift
+// RUN: %target-swift-frontend -module-name enum_resilience -I %t -emit-ir -enable-resilience %s | %FileCheck %s -DINT=i%target-ptrsize
+// RUN: %target-swift-frontend -module-name enum_resilience -I %t -emit-ir -enable-resilience -O %s
+
+// REQUIRES: objc_interop
+
+// Because the enum is resilient we cannot pack the tag into the pointer inside of the resilient payload.
+// CHECK: %T15enum_resilience9ContainerC5Multi33_{{.*}}LLO.0 = type <{ [{{(8|4)}} x i8], [1 x i8] }>
+
+import resilient_struct
+
+public class Container {
+  private enum Multi {
+    case none
+    case some(Container)
+    case data(ResilientRef)
+  }
+  private var e: Multi
+  var i: Int
+  init() {
+    e = .none
+    i = 0
+  }
+}

test/Inputs/resilient_struct.swift

@@ -77,3 +77,17 @@ public struct ResilientDouble {
     self.d = d
   }
 }
+
+public class Referent {}
+
+public struct ResilientWeakRef {
+  public weak var ref: Referent?
+
+  public init (_ r: Referent) {
+    ref = r
+  }
+}
+
+public struct ResilientRef {
+  public var r: Referent
+}

test/Interpreter/enum_resilience.swift

@@ -436,4 +436,28 @@ ResilientEnumTestSuite.test("ResilientEnumExtension") {
   expectEqual(Base.self, ResilientMultiPayloadGenericEnumFixedSize<Base>.A.getTypeParameter())
 }
 
+public class Container {
+  private enum Multi {
+    case none
+    case some(Container)
+    case other(ResilientRef)
+  }
+  private var m: Multi
+  var i: Int
+  init() {
+    m = .none
+    i = 0
+    switch self.m {
+      case .none:
+        print("success")
+      case .some(_), .other(_):
+        assert(false, "noooo!")
+    }
+  }
+}
+
+ResilientEnumTestSuite.test("ResilientPrivateEnumMember") {
+  _ = Container()
+}
+
 runAllTests()