Add tests for SendableProhibitsMainActorInference

Author: DougGregor

test/Concurrency/assume_mainactor_typechecker_errors_sendablecheck.swift

@@ -0,0 +1,16 @@
+// RUN: %target-swift-frontend -swift-version 5 -emit-sil -default-isolation MainActor %s -verify -verify-additional-prefix swift5- -enable-experimental-feature SendableProhibitsMainActorInference
+// RUN: %target-swift-frontend -swift-version 6 -emit-sil -default-isolation MainActor %s -verify -verify-additional-prefix swift6- -enable-experimental-feature SendableProhibitsMainActorInference
+
+// REQUIRES: swift_feature_SendableProhibitsMainActorInference
+
+// Ensure that a Sendable-conforming protocol suppresses @MainActor inference
+// for a type.
+enum CK: CodingKey {
+  case one
+
+  func f() { }
+}
+
+nonisolated func testCK(x: CK) {
+  x.f() // okay, because CK and CK.f are not @MainActor.
+}

test/Macros/default_main_actor_nonisolated.swift

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+// REQUIRES: swift_swift_parser, executable_test
+
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+
+// Check for errors
+// RUN: %target-swift-frontend -swift-version 5 -typecheck -load-plugin-library %t/%target-library-name(MacroDefinition) %s -I %t -disable-availability-checking -swift-version 6 -default-isolation MainActor -enable-experimental-feature SendableProhibitsMainActorInference
+
+
+@attached(extension, conformances: Sendable)
+macro AddSendable() = #externalMacro(module: "MacroDefinition", type: "SendableMacro")
+
+@AddSendable
+final class SendableClass {
+  var property: Int { 0 }
+
+  func f() { }
+}
+
+nonisolated func acceptSendable<T: Sendable>(_: T) { }
+
+@concurrent func test(sc: SendableClass) async {
+  acceptSendable(sc) // SendableClass is Sendable
+  acceptSendable(\SendableClass.property) // so is its property
+  sc.f() // not on the main actor, so this is okay
+}