Merge pull request swiftlang#34468 from kavon/objc-async-70543421

[concurrency] Overload resolution for async-looking ObjC methods

Author: DougGregor

lib/Sema/CSStep.cpp

@@ -578,13 +578,15 @@ bool DisjunctionStep::shouldStopAt(const DisjunctionChoice &choice) const {
   auto delta = LastSolvedChoice->second - getCurrentScore();
   bool hasUnavailableOverloads = delta.Data[SK_Unavailable] > 0;
   bool hasFixes = delta.Data[SK_Fix] > 0;
+  bool hasAsyncMismatch = delta.Data[SK_AsyncSyncMismatch] > 0;
   auto isBeginningOfPartition = choice.isBeginningOfPartition();
 
   // Attempt to short-circuit evaluation of this disjunction only
-  // if the disjunction choice we are comparing to did not involve
-  // selecting unavailable overloads or result in fixes being
-  // applied to reach a solution.
-  return !hasUnavailableOverloads && !hasFixes &&
+  // if the disjunction choice we are comparing to did not involve:
+  //   1. selecting unavailable overloads
+  //   2. result in fixes being applied to reach a solution
+  //   3. selecting an overload that results in an async/sync mismatch
+  return !hasUnavailableOverloads && !hasFixes && !hasAsyncMismatch &&
          (isBeginningOfPartition ||
           shortCircuitDisjunctionAt(choice, lastChoice));
 }

test/Concurrency/Inputs/Delegate.h

@@ -0,0 +1,21 @@
+#ifndef Delegate_h
+#define Delegate_h
+
+@import Foundation;
+
+@interface Request : NSObject
+
+@end
+
+@interface Delegate : NSObject
+
+- (void)makeRequest1:(Request * _Nonnull)request completionHandler:(void (^ _Nullable)(void))handler;
+
+- (void)makeRequest2:(NSObject * _Nonnull)request completionHandler:(void (^ _Nullable)(void))handler;
+
+- (void)makeRequest3:(Request * _Nullable)request completionHandler:(void (^ _Nullable)(void))handler;
+
+@end
+
+
+#endif

test/Concurrency/objc_async_overload.swift

@@ -0,0 +1,31 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-experimental-concurrency -typecheck -verify -import-objc-header %S/Inputs/Delegate.h %s
+
+// REQUIRES: objc_interop
+
+
+// overload resolution should pick sync version in a sync context
+func syncContext() {
+  let r = Request()
+  let d = Delegate()
+  d.makeRequest1(r) // NOTE: this use to trigger an overload resolution error, see SR-13760
+  d.makeRequest2(r)
+  d.makeRequest3(r)
+}
+
+// overload resolution should pick async version in an async context
+func asyncNoAwait() async {
+  let r = Request()
+  let d = Delegate()
+  d.makeRequest1(r) // expected-error {{call is 'async' but is not marked with 'await'}}
+  d.makeRequest2(r) // expected-error {{call is 'async' but is not marked with 'await'}}
+  d.makeRequest3(r) // expected-error {{call is 'async' but is not marked with 'await'}}
+}
+
+
+func asyncWithAwait() async {
+  let r = Request()
+  let d = Delegate()
+  await d.makeRequest1(r)
+  await d.makeRequest2(r)
+  await d.makeRequest3(r)
+}