Don't infer 'nonisolated' on stored properties.

Fixes rdar://80424675.

Author: DougGregor

lib/Sema/TypeCheckConcurrency.cpp

@@ -3266,6 +3266,13 @@ ActorIsolation ActorIsolationRequest::evaluate(
     ASTContext &ctx = value->getASTContext();
     switch (inferred) {
     case ActorIsolation::Independent:
+      // Stored properties cannot be non-isolated, so don't infer it.
+      if (auto var = dyn_cast<VarDecl>(value)) {
+        if (!var->isStatic() && var->hasStorage())
+          return ActorIsolation::forUnspecified();
+      }
+
+
       if (onlyGlobal)
         return ActorIsolation::forUnspecified();
 

test/Concurrency/global_actor_inference.swift

@@ -94,6 +94,17 @@ func testNotAllInP1(nap1: NotAllInP1) { // expected-note{{add '@SomeGlobalActor'
   nap1.other() // okay
 }
 
+// Make sure we don't infer 'nonisolated' for stored properties.
+@MainActor
+protocol Interface {
+  nonisolated var baz: Int { get } // expected-note{{'baz' declared here}}
+}
+
+@MainActor
+class Object: Interface {
+  var baz: Int = 42 // expected-warning{{property 'baz' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Interface'}}
+}
+
 
 // ----------------------------------------------------------------------
 // Global actor inference for classes and extensions