Merge pull request #68612 from kavon/generic-params-isolated

[Concurrency] tighten-up rules about isolated generic parameters

Author: kavon

include/swift/AST/DiagnosticsSema.def

@@ -5331,6 +5331,9 @@ NOTE(protocol_isolated_to_global_actor_here,none,
 
 ERROR(isolated_parameter_not_actor,none,
       "'isolated' parameter has non-actor type %0", (Type))
+ERROR(isolated_parameter_no_actor_conformance,none,
+      "'isolated' parameter %0 must conform to 'Actor' "
+      "or 'DistributedActor' protocol", (Type))
 ERROR(isolated_parameter_duplicate,none,
       "cannot have more than one 'isolated' parameter", ())
 ERROR(isolated_parameter_duplicate_type,none,

lib/Sema/TypeCheckConcurrency.cpp

@@ -4092,12 +4092,26 @@ ActorIsolation ActorIsolationRequest::evaluate(
   if (auto paramIdx = getIsolatedParamIndex(value)) {
     checkDeclWithIsolatedParameter(value);
 
-    // FIXME: This doesn't allow us to find an Actor or DistributedActor
-    // bound on the parameter type effectively.
-    auto param = getParameterList(value)->get(*paramIdx);
+    ParamDecl *param = getParameterList(value)->get(*paramIdx);
     Type paramType = param->getInterfaceType();
     if (paramType->isTypeParameter()) {
       paramType = param->getDeclContext()->mapTypeIntoContext(paramType);
+
+      auto &ctx = value->getASTContext();
+      auto conformsTo = [&](KnownProtocolKind kind) {
+        if (auto *proto = ctx.getProtocol(kind))
+          return value->getModuleContext()->conformsToProtocol(paramType, proto);
+        return ProtocolConformanceRef::forInvalid();
+      };
+
+      // The type parameter must be bound by Actor or DistributedActor, as they
+      // have an unownedExecutor. AnyActor does NOT have an unownedExecutor!
+      if (!conformsTo(KnownProtocolKind::Actor)
+          && !conformsTo(KnownProtocolKind::DistributedActor)) {
+        ctx.Diags.diagnose(param->getLoc(),
+                           diag::isolated_parameter_no_actor_conformance,
+                           paramType);
+      }
     }
 
     if (auto actor = paramType->getAnyActor())

test/Concurrency/isolated_parameters.swift

@@ -348,3 +348,12 @@ func getValues(
     actor.dictionary[key]
   }
 }
+
+func isolated_generic_bad_1<T>(_ t: isolated T) {}
+// expected-error@-1 {{'isolated' parameter 'T' must conform to 'Actor' or 'DistributedActor' protocol}}
+func isolated_generic_bad_2<T: Equatable>(_ t: isolated T) {}
+// expected-error@-1 {{'isolated' parameter 'T' must conform to 'Actor' or 'DistributedActor' protocol}}
+func isolated_generic_bad_3<T: AnyActor>(_ t: isolated T) {}
+// expected-error@-1 {{'isolated' parameter 'T' must conform to 'Actor' or 'DistributedActor' protocol}}
+
+func isolated_generic_ok_1<T: Actor>(_ t: isolated T) {}

test/Distributed/distributed_actor_isolation.swift

@@ -258,3 +258,5 @@ extension Greeting where SerializationRequirement == Codable {
     try await greetLocal(name: "Alice") // expected-error{{only 'distributed' instance methods can be called on a potentially remote distributed actor}}
   }
 }
+
+func isolated_generic_ok<T: DistributedActor>(_ t: isolated T) {}