[Concurrency] Don't walk into sending closures when computing the

required isolation of a default value expression.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -2703,7 +2703,8 @@ namespace {
               // function type, but this is okay for non-Sendable closures
               // because they cannot leave the isolation domain they're created
               // in anyway.
-              if (closure->isSendable())
+              if (isIsolationInferenceBoundaryClosure(
+                      closure, /*can inherit actor context*/false))
                 return false;
 
               if (closure->getActorIsolation().isActorIsolated())

test/Concurrency/isolated_default_arguments.swift

@@ -214,6 +214,18 @@ class C3 {
   @SomeGlobalActor var y = 2
 }
 
+class C4 {
+  let task1 = Task {
+    // expected-error@+2 {{expression is 'async' but is not marked with 'await'}}
+    // expected-note@+1 {{calls to global function 'requiresMainActor()' from outside of its actor context are implicitly asynchronous}}
+    requiresMainActor()
+  }
+
+  let task2 = Task {
+    await requiresMainActor() // okay
+  }
+}
+
 @MainActor struct NonIsolatedInit {
   var x = 0
   var y = 0

test/Concurrency/isolated_default_property_inits.swift

@@ -8,6 +8,10 @@
 // REQUIRES: concurrency
 // REQUIRES: asserts
 
+// This tests errors emitted in definite initialization; this test file cannot
+// have any type checker errors. Type checker errors for IsolatedDefaultValues
+// are tested in isolated_default_arguments.swift
+
 @globalActor
 actor SomeGlobalActor {
   static let shared = SomeGlobalActor()