[Feataures] Add an upcoming feature flag for complete concurrency checking.

Author: hborla

include/swift/Basic/Features.def

@@ -115,6 +115,7 @@ SUPPRESSIBLE_LANGUAGE_FEATURE(RetroactiveAttribute, 364, "@retroactive", true)
 
 UPCOMING_FEATURE(ConciseMagicFile, 274, 6)
 UPCOMING_FEATURE(ForwardTrailingClosures, 286, 6)
+UPCOMING_FEATURE(CompleteConcurrency, 0337, 6)
 UPCOMING_FEATURE(BareSlashRegexLiterals, 354, 6)
 UPCOMING_FEATURE(DeprecateApplicationMain, 383, 6)
 UPCOMING_FEATURE(ImportObjcForwardDeclarations, 384, 6)

lib/AST/ASTPrinter.cpp

@@ -3311,6 +3311,10 @@ static bool usesFeatureForwardTrailingClosures(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureCompleteConcurrency(Decl *decl) {
+  return false;
+}
+
 static bool usesFeatureBareSlashRegexLiterals(Decl *decl) {
   return false;
 }

lib/Frontend/CompilerInvocation.cpp

@@ -888,6 +888,12 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Opts.Features.insert(*feature);
   }
 
+  // CompleteConcurrency enables all data-race safety upcoming features.
+  if (Opts.hasFeature(Feature::CompleteConcurrency)) {
+    Opts.StrictConcurrencyLevel = StrictConcurrency::Complete;
+    Opts.Features.insert(Feature::DisableOutwardActorInference);
+  }
+
   // Map historical flags over to experimental features. We do this for all
   // compilers because that's how existing experimental feature flags work.
   if (Args.hasArg(OPT_enable_experimental_static_assert))
@@ -1002,7 +1008,8 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   } else if (Args.hasArg(OPT_warn_concurrency)) {
     Opts.StrictConcurrencyLevel = StrictConcurrency::Complete;
-  } else if (Opts.hasFeature(Feature::StrictConcurrency)) {
+  } else if (Opts.hasFeature(Feature::CompleteConcurrency) ||
+             Opts.hasFeature(Feature::StrictConcurrency)) {
     // Already set above.
   } else {
     // Default to minimal checking in Swift 5.x.

test/Concurrency/complete_concurrency.swift

@@ -0,0 +1,30 @@
+// RUN: %target-swift-frontend -disable-availability-checking -parse-as-library -enable-upcoming-feature CompleteConcurrency -emit-sil -o /dev/null -verify %s
+
+// REQUIRES: concurrency
+
+// expected-note@+1 {{class 'NonSendable' does not conform to the 'Sendable' protocol}}
+class NonSendable {}
+
+@MainActor func onMain(ns: NonSendable) async {
+  // expected-warning@+1 {{passing argument of non-sendable type 'NonSendable' outside of main actor-isolated context may introduce data races}}
+  await onGeneric(ns: ns)
+}
+
+@propertyWrapper
+struct Wrapper {
+  // expected-note@+1 {{mutation of this property is only permitted within the actor}}
+  @preconcurrency @MainActor var wrappedValue: NonSendable
+
+  init(wrappedValue: NonSendable) {
+    // expected-warning@+1 {{main actor-isolated property 'wrappedValue' can not be mutated from a non-isolated context; this is an error in Swift 6}}
+    self.wrappedValue = wrappedValue
+  }
+}
+
+struct S {
+  @Wrapper var value: NonSendable = NonSendable()
+}
+
+nonisolated func onGeneric(ns: NonSendable) async {
+  let _ = S()
+}