[Concurrency] Finish and add tests for ban on async with @objc.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -4369,6 +4369,8 @@ NOTE(not_objc_generic_type_param,none,
 NOTE(not_objc_function_type_param,none,
      "function types cannot be represented in Objective-C unless their "
      "parameters and returns can be", ())
+ERROR(not_objc_function_async,none,
+      "'async' function cannot be represented in Objective-C", ())
 NOTE(not_objc_function_type_async,none,
       "'async' function types cannot be represented in Objective-C", ())
 NOTE(not_objc_function_type_throwing,none,

lib/Sema/TypeCheckDeclObjC.cpp

@@ -613,6 +613,16 @@ bool swift::isRepresentableInObjC(
     }
   }
 
+  // Async functions cannot be mapped into Objective-C.
+  if (AFD->hasAsync()) {
+    if (Diagnose) {
+      AFD->diagnose(diag::not_objc_function_async)
+        .highlight(AFD->getAsyncLoc());
+      describeObjCReason(AFD, Reason);
+    }
+    return false;
+  }
+
   // Throwing functions must map to a particular error convention.
   if (AFD->hasThrows()) {
     DeclContext *dc = const_cast<AbstractFunctionDecl *>(AFD);

test/attr/attr_objc.swift

@@ -1,6 +1,6 @@
-// RUN: %target-swift-frontend -disable-objc-attr-requires-foundation-module -typecheck -verify -verify-ignore-unknown %s -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference
-// RUN: %target-swift-ide-test -skip-deinit=false -print-ast-typechecked -source-filename %s -function-definitions=true -prefer-type-repr=false -print-implicit-attrs=true -explode-pattern-binding-decls=true -disable-objc-attr-requires-foundation-module -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference | %FileCheck %s
-// RUN: not %target-swift-frontend -typecheck -dump-ast -disable-objc-attr-requires-foundation-module %s -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference > %t.ast
+// RUN: %target-swift-frontend -disable-objc-attr-requires-foundation-module -typecheck -verify -verify-ignore-unknown %s -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference -enable-experimental-concurrency
+// RUN: %target-swift-ide-test -skip-deinit=false -print-ast-typechecked -source-filename %s -function-definitions=true -prefer-type-repr=false -print-implicit-attrs=true -explode-pattern-binding-decls=true -disable-objc-attr-requires-foundation-module -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference -enable-experimental-concurrency | %FileCheck %s
+// RUN: not %target-swift-frontend -typecheck -dump-ast -disable-objc-attr-requires-foundation-module %s -swift-version 4 -enable-source-import -I %S/Inputs -enable-swift3-objc-inference -enable-experimental-concurrency > %t.ast
 // RUN: %FileCheck -check-prefix CHECK-DUMP %s < %t.ast
 // REQUIRES: objc_interop
 
@@ -2381,3 +2381,11 @@ class SR12801 {
   @objc subscript<T>(foo : [T]) -> Int { return 0 }
   // expected-error@-1 {{subscript cannot be marked @objc because it has generic parameters}}
 }
+
+// async cannot be compiled with @objc.
+class Concurrency {
+  @objc func doBigJob() async -> Int { return 0 } // expected-error{{'async' function cannot be represented in Objective-C}}
+
+  @objc func takeAnAsync(_ fn: () async -> Int) { } // expected-error{{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
+  // expected-note@-1{{'async' function types cannot be represented in Objective-C}}
+}

tools/swift-ide-test/swift-ide-test.cpp

@@ -756,6 +756,12 @@ static llvm::cl::opt<std::string>
 ExplicitSwiftModuleMap("explicit-swift-module-map-file",
                        llvm::cl::desc("JSON file to include explicit Swift modules"),
                        llvm::cl::cat(Category));
+
+static llvm::cl::opt<bool>
+EnableExperimentalConcurrency("enable-experimental-concurrency",
+                              llvm::cl::desc("Enable experimental concurrency model"),
+                              llvm::cl::init(false));
+
 } // namespace options
 
 static std::unique_ptr<llvm::MemoryBuffer>
@@ -3820,6 +3826,9 @@ int main(int argc, char *argv[]) {
   if (options::EnableCxxInterop) {
     InitInvok.getLangOptions().EnableCXXInterop = true;
   }
+  if (options::EnableExperimentalConcurrency) {
+    InitInvok.getLangOptions().EnableExperimentalConcurrency = true;
+  }
 
   // We disable source location resolutions from .swiftsourceinfo files by
   // default to match sourcekitd-test's and ide clients' expected behavior