Merge pull request #60431 from angela-laar/enable-existential-any

Enforce existential `any` behind a feature flag

Author: angela-laar

include/swift/Basic/Features.def

@@ -93,6 +93,7 @@ SUPPRESSIBLE_LANGUAGE_FEATURE(NoAsyncAvailability, 340, "@available(*, noasync)"
 UPCOMING_FEATURE(ConciseMagicFile, 274, 6)
 UPCOMING_FEATURE(ForwardTrailingClosures, 286, 6)
 UPCOMING_FEATURE(BareSlashRegexLiterals, 354, 6)
+UPCOMING_FEATURE(ExistentialAny, 335, 6)
 
 EXPERIMENTAL_FEATURE(StaticAssert)
 EXPERIMENTAL_FEATURE(VariadicGenerics)

lib/AST/ASTPrinter.cpp

@@ -3010,6 +3010,10 @@ static bool usesFeatureConciseMagicFile(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureExistentialAny(Decl *decl) {
+  return false;
+}
+
 static bool usesFeatureForwardTrailingClosures(Decl *decl) {
   return false;
 }

lib/Sema/TypeCheckDecl.cpp

@@ -708,6 +708,10 @@ ExistentialConformsToSelfRequest::evaluate(Evaluator &evaluator,
 bool
 ExistentialRequiresAnyRequest::evaluate(Evaluator &evaluator,
                                         ProtocolDecl *decl) const {
+  auto &ctx = decl->getASTContext();
+  if (ctx.LangOpts.hasFeature(Feature::ExistentialAny))
+    return true;
+
   // ObjC protocols do not require `any`.
   if (decl->isObjC())
     return false;

test/Concurrency/actor_isolation_swift6.swift

@@ -59,7 +59,7 @@ func checkIsolationValueType(_ formance: InferredFromConformance,
   _ = await anno.counter  // expected-warning {{no 'async' operations occur within 'await' expression}}
 
   // these do need await, regardless of reference or value type
-  _ = await (formance as MainCounter).counter
+  _ = await (formance as any MainCounter).counter
   _ = await ext[1]
   _ = await formance.ticker
   _ = await ext.polygon