Don't actually warn about about the property wrapper isolation in Swift 5.

In many cases, the inferrence was unexpected and undesired. We shouldn't warn the user about something that is reasonably likely to be correct.

(cherry picked from commit a1ea822)

Author: bjhomer

include/swift/AST/DiagnosticsSema.def

@@ -5364,12 +5364,6 @@ ERROR(async_unavailable_decl,none,
       "%0 %1 is unavailable from asynchronous contexts%select{|; %2}2",
       (DescriptiveDeclKind, DeclBaseName, StringRef))
 
-WARNING(actor_isolation_inferred_from_property_wrapper,none,
-        "%0 is implicitly %1 because it uses %2. This implicit isolation "
-        "will no longer happen in Swift 6.",
-        (DeclName, ActorIsolation, StringRef))
-
-
 //------------------------------------------------------------------------------
 // MARK: String Processing
 //------------------------------------------------------------------------------

lib/Sema/TypeCheckConcurrency.cpp

@@ -3625,13 +3625,12 @@ static Optional<ActorIsolation> getIsolationFromWrappers(
 
   ASTContext &ctx = nominal->getASTContext();
   if (ctx.isSwiftVersionAtLeast(6)) {
-    // In Swift 6, we no longer infer isolation of a nominal type based
-    // on property wrappers used in its stored properties
+    // In Swift 6, we no longer infer isolation of a nominal type
+    // based on the property wrappers used in its stored properties
     return None;
   }
 
-  Optional<std::pair<ActorIsolation, Type>> foundIsolationAndType;
-
+  Optional<ActorIsolation> foundIsolation;
   for (auto member : nominal->getMembers()) {
     auto var = dyn_cast<VarDecl>(member);
     if (!var || !var->isInstanceMember())
@@ -3656,36 +3655,19 @@ static Optional<ActorIsolation> getIsolationFromWrappers(
 
     case ActorIsolation::GlobalActor:
     case ActorIsolation::GlobalActorUnsafe:
-      if (!foundIsolationAndType) {
-        if (auto propertyWrapperType = var->getAttachedPropertyWrapperType(0)) {
-          foundIsolationAndType = { isolation, propertyWrapperType };
-          continue;
-        }
+      if (!foundIsolation) {
+        foundIsolation = isolation;
+        continue;
       }
 
-      if (foundIsolationAndType->first != isolation)
+      if (*foundIsolation != isolation)
         return None;
 
       break;
     }
   }
 
-  if (foundIsolationAndType) {
-    // We are inferring isolation for the type because
-    // it contains an actor-isolated property wrapper.
-    // Warn that this inferrence will be going away in
-    // Swift 6
-    const ActorIsolation isolation = foundIsolationAndType->first;
-    const Type type = foundIsolationAndType->second;
-
-    nominal->diagnose(diag::actor_isolation_inferred_from_property_wrapper,
-                      nominal->getName(), isolation, "'@"+type->getString()+"'")
-      .fixItInsert(nominal->getAttributeInsertionLoc(false), "@" + isolation.getGlobalActor().getString());
-    return isolation;
-  }
-  else {
-    return None;
-  }
+  return foundIsolation;
 }
 
 namespace {