[Concurrency] Don't diagnose metatype captures in closures that are

isolated to the same actor as the enclosing context.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -2543,7 +2543,8 @@ namespace {
     /// Determine whether code in the given use context might execute
     /// concurrently with code in the definition context.
     bool mayExecuteConcurrentlyWith(
-        const DeclContext *useContext, const DeclContext *defContext);
+        const DeclContext *useContext, const DeclContext *defContext,
+        bool includeSending = false);
 
     /// If the subexpression is a reference to a mutable local variable from a
     /// different context, record its parent. We'll query this as part of
@@ -3051,12 +3052,9 @@ namespace {
         }
       }
 
-      // FIXME: When passing to a sending parameter, should this be handled
-      // by region isolation? Or should it always be handled by region
-      // isolation?
       if (mayExecuteConcurrentlyWith(
-              localFunc.getAsDeclContext(), getDeclContext()) ||
-          (explicitClosure && explicitClosure->isPassedToSendingParameter())) {
+              localFunc.getAsDeclContext(), getDeclContext(),
+              /*includeSending*/true)) {
         auto innermostGenericDC = localFunc.getAsDeclContext();
         while (innermostGenericDC && !innermostGenericDC->isGenericContext())
           innermostGenericDC = innermostGenericDC->getParent();
@@ -4816,7 +4814,8 @@ ActorIsolation ActorIsolationChecker::determineClosureIsolation(
 }
 
 bool ActorIsolationChecker::mayExecuteConcurrentlyWith(
-    const DeclContext *useContext, const DeclContext *defContext) {
+    const DeclContext *useContext, const DeclContext *defContext,
+    bool includeSending) {
   // Fast path for when the use and definition contexts are the same.
   if (useContext == defContext)
     return false;
@@ -4847,6 +4846,10 @@ bool ActorIsolationChecker::mayExecuteConcurrentlyWith(
       if (closure->isSendable())
         return true;
 
+      if (auto *explicitClosure = dyn_cast<ClosureExpr>(closure)) {
+        if (includeSending && explicitClosure->isPassedToSendingParameter())
+          return true;
+      }
     }
 
     if (auto func = dyn_cast<FuncDecl>(useContext)) {

test/Concurrency/sendable_metatype_typecheck.swift

@@ -175,3 +175,16 @@ extension TestUnapplied {
 func testUnappliedWithOpetator<T: Comparable>(v: TestUnapplied<T>) {
   v<=>(>) // expected-error {{converting non-Sendable function value to '@Sendable (T, T) -> Bool' may introduce data races}}
 }
+
+protocol P {}
+
+func acceptClosure(_: () -> Void) {}
+
+@MainActor
+func f<T: P>(_: T.Type) {
+  acceptClosure {
+    Task {
+      _ = T.self // okay to capture T.Type in this closure.
+    }
+  }
+}