Merge pull request #70743 from hborla/inferred-preconcurrency

[Concurrency] Downgrade isolated call diagnostics when the callee has an inferred `@preconcurrency` annotation.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -3341,7 +3341,7 @@ namespace {
         } else {
           if (calleeDecl) {
             auto preconcurrency = getContextIsolation().preconcurrency() ||
-            calleeDecl->preconcurrency();
+                getActorIsolation(calleeDecl).preconcurrency();
             ctx.Diags.diagnose(
                                apply->getLoc(), diag::actor_isolated_call_decl,
                                *unsatisfiedIsolation,
@@ -5135,7 +5135,8 @@ bool swift::contextRequiresStrictConcurrencyChecking(
       // features.
       if (auto *extension = dyn_cast<ExtensionDecl>(decl)) {
         auto *nominal = extension->getExtendedNominal();
-        if (nominal && hasExplicitIsolationAttribute(nominal))
+        if (nominal && hasExplicitIsolationAttribute(nominal) &&
+            !getActorIsolation(nominal).preconcurrency())
           return true;
       }
 

test/Concurrency/predates_concurrency.swift

@@ -103,8 +103,8 @@ func testCalls(x: X) {
   let _: () -> Void = onMainActorAlways // expected-complete-tns-warning {{converting function value of type '@MainActor () -> ()' to '() -> Void' loses global actor 'MainActor'}}
 
   // both okay with minimal/targeted... an error with complete.
-  let c = MyModelClass() // expected-complete-tns-error {{call to main actor-isolated initializer 'init()' in a synchronous nonisolated context}}
-  c.f() // expected-complete-tns-error {{call to main actor-isolated instance method 'f()' in a synchronous nonisolated context}}
+  let c = MyModelClass() // expected-complete-tns-warning {{call to main actor-isolated initializer 'init()' in a synchronous nonisolated context}}
+  c.f() // expected-complete-tns-warning {{call to main actor-isolated instance method 'f()' in a synchronous nonisolated context}}
 }
 
 func testCallsWithAsync() async {
@@ -207,3 +207,41 @@ class C { // expected-complete-tns-note {{'C' does not conform to the 'Sendable'
   }
 }
 
+@preconcurrency @MainActor
+class MainActorPreconcurrency {}
+
+class InferMainActorPreconcurrency: MainActorPreconcurrency {
+  static func predatesConcurrency() {}
+  // expected-note@-1 {{calls to static method 'predatesConcurrency()' from outside of its actor context are implicitly asynchronous}}
+}
+
+nonisolated func blah() {
+  InferMainActorPreconcurrency.predatesConcurrency()
+  // expected-warning@-1 {{call to main actor-isolated static method 'predatesConcurrency()' in a synchronous nonisolated context}}
+}
+
+protocol NotIsolated {
+  func requirement()
+  // expected-complete-tns-note@-1 {{mark the protocol requirement 'requirement()' 'async' to allow actor-isolated conformances}}
+}
+
+extension MainActorPreconcurrency: NotIsolated {
+  func requirement() {}
+  // expected-complete-tns-warning@-1 {{main actor-isolated instance method 'requirement()' cannot be used to satisfy nonisolated protocol requirement}}
+  // expected-complete-tns-note@-2 {{add 'nonisolated' to 'requirement()' to make this instance method not isolated to the actor}}
+  // expected-complete-tns-note@-3 {{calls to instance method 'requirement()' from outside of its actor context are implicitly asynchronous}}
+
+
+  class Nested {
+    weak var c: MainActorPreconcurrency?
+
+    func test() {
+    // expected-complete-tns-note@-1 {{add '@MainActor' to make instance method 'test()' part of global actor 'MainActor'}}
+
+      if let c {
+        c.requirement()
+        // expected-complete-tns-warning@-1 {{call to main actor-isolated instance method 'requirement()' in a synchronous nonisolated context}}
+      }
+    }
+  }
+}