[region-isolation] Teach region isolation how to handle cases where due to compiler bugs, we have a function isolated to self without an isolated parameter.

Closures generally only inherit actor instance isolation if they directly
capture state from the actor instance. In this case, for some reason that is not
true, so we hit an assert that assumes that we will only see a global actor
isolated isolation.

Region Isolation should be able to handle code even if the closure isolation
invariant is violated by the frontend. So to do this, I am introducing a new
singleton actor instance to represent the isolation of a defer or closure
created in an actor instance isolated method. The reason why I am using a
singleton is that closures and defer are not methods so we do not actually know
which parameter is 'self' since it isn't in the abi. But we still need some
value to represent the captured values as belonging to. To square this circle, I
just did what we have done in a similar situation where we did not have a value:
(ActorAccessorInit). In that case, we just use a sentinel to represent the
instance (NOTE: This is represented just via a kind so ActorInstances that are
operator== equal will not &value equal since we are just using a kind).

Author: gottesmm

include/swift/SILOptimizer/Utils/SILIsolationInfo.h

@@ -46,11 +46,18 @@ class ActorInstance {
     /// access to the self value and instead have access indirectly to the
     /// storage associated with the accessor.
     ActorAccessorInit = 0x1,
+
+    /// An actor instance that is represented by "self" being captured in a
+    /// closure of some sort. In such a case, we do not know which of the
+    /// parameters are the true "self" (since the closure is a thin
+    /// function)... so we just use an artificial ActorInstance to represent
+    /// self in this case.
+    CapturedActorSelf = 0x2,
   };
 
-  /// Set to (SILValue(), ActorAccessorInit) if we have an ActorAccessorInit. Is
-  /// null if we have (SILValue(), Kind::Value).
-  llvm::PointerIntPair<SILValue, 1> value;
+  /// Set to (SILValue(), $KIND) if we have an ActorAccessorInit|CapturedSelf.
+  /// Is null if we have (SILValue(), Kind::Value).
+  llvm::PointerIntPair<SILValue, 2> value;
 
   ActorInstance(SILValue value, Kind kind)
       : value(value, std::underlying_type<Kind>::type(kind)) {}
@@ -68,10 +75,18 @@ class ActorInstance {
     return ActorInstance(value, Kind::Value);
   }
 
+  /// See Kind::ActorAccessorInit for explanation on what a ActorAccessorInit
+  /// is.
   static ActorInstance getForActorAccessorInit() {
     return ActorInstance(SILValue(), Kind::ActorAccessorInit);
   }
 
+  /// See Kind::CapturedActorSelf for explanation on what a CapturedActorSelf
+  /// is.
+  static ActorInstance getForCapturedSelf() {
+    return ActorInstance(SILValue(), Kind::CapturedActorSelf);
+  }
+
   explicit operator bool() const { return bool(value.getOpaqueValue()); }
 
   Kind getKind() const { return Kind(value.getInt()); }
@@ -91,6 +106,10 @@ class ActorInstance {
 
   bool isAccessorInit() const { return getKind() == Kind::ActorAccessorInit; }
 
+  bool isCapturedActorSelf() const {
+    return getKind() == Kind::CapturedActorSelf;
+  }
+
   bool operator==(const ActorInstance &other) const {
     // If both are null, return true.
     if (!bool(*this) && !bool(other))
@@ -105,6 +124,7 @@ class ActorInstance {
     case Kind::Value:
       return getValue() == other.getValue();
     case Kind::ActorAccessorInit:
+    case Kind::CapturedActorSelf:
       return true;
     }
   }

lib/SILOptimizer/Utils/SILIsolationInfo.cpp

@@ -879,8 +879,14 @@ SILIsolationInfo SILIsolationInfo::get(SILArgument *arg) {
   if (auto functionIsolation = fArg->getFunction()->getActorIsolation()) {
     if (functionIsolation.isActorIsolated()) {
       assert(functionIsolation.isGlobalActor());
-      return SILIsolationInfo::getGlobalActorIsolated(
-          fArg, functionIsolation.getGlobalActor());
+      if (functionIsolation.isGlobalActor()) {
+        return SILIsolationInfo::getGlobalActorIsolated(
+            fArg, functionIsolation.getGlobalActor());
+      }
+
+      return SILIsolationInfo::getActorInstanceIsolated(
+          fArg, ActorInstance::getForActorAccessorInit(),
+          functionIsolation.getActor());
     }
   }
 
@@ -944,6 +950,12 @@ void SILIsolationInfo::print(llvm::raw_ostream &os) const {
         os << '\n';
         os << "instance: actor accessor init\n";
         return;
+      case ActorInstance::Kind::CapturedActorSelf:
+        os << "'self'-isolated";
+        printOptions(os);
+        os << '\n';
+        os << "instance: captured actor instance self\n";
+        return;
       }
     }
 
@@ -1062,6 +1074,9 @@ void SILIsolationInfo::printForDiagnostics(llvm::raw_ostream &os) const {
       case ActorInstance::Kind::ActorAccessorInit:
         os << "'self'-isolated";
         return;
+      case ActorInstance::Kind::CapturedActorSelf:
+        os << "'self'-isolated";
+        return;
       }
     }
 
@@ -1102,7 +1117,11 @@ void SILIsolationInfo::printForOneLineLogging(llvm::raw_ostream &os) const {
         break;
       }
       case ActorInstance::Kind::ActorAccessorInit:
-        os << "'self'-isolated";
+        os << "'self'-isolated (actor-accessor-init)";
+        printOptions(os);
+        return;
+      case ActorInstance::Kind::CapturedActorSelf:
+        os << "'self'-isolated (captured-actor-self)";
         printOptions(os);
         return;
       }

test/Concurrency/Inputs/transfernonsendable_crashers_objc.h

@@ -1,5 +1,11 @@
 
+@import Foundation;
+
 @interface MyNotificationCenter
 - (id)init;
 - (void)post;
 @end
+
+@protocol MySession <NSObject>
+- (void)endSession;
+@end

test/Concurrency/transfernonsendable_crashers_objc.swift

@@ -18,3 +18,10 @@ public func handleFile(at location: URL) throws {
 
 private func moveTheme(from location: URL) throws -> URL { fatalError() }
 private func unzipFile(at location: URL) throws -> URL { fatalError() }
+
+actor MyActor {
+  func test() {
+    var session: MySession?
+    defer { session?.end() }
+  }
+}