Merge pull request swiftlang#37020 from DougGregor/async-operation-5.5

DougGregor · web-flow · commit 62a2a739d38d · 2021-04-23T01:23:44.000-07:00
[5.5] [Concurrency] Add "async" operation for continuing work asynchronously.
diff --git a/include/swift/AST/Attr.def b/include/swift/AST/Attr.def
@@ -652,6 +652,11 @@ SIMPLE_DECL_ATTR(_implicitSelfCapture, ImplicitSelfCapture,
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIBreakingToRemove,
   115)
 
+SIMPLE_DECL_ATTR(_inheritActorContext, InheritActorContext,
+  OnParam | UserInaccessible |
+  ABIStableToAdd | ABIStableToRemove | APIBreakingToAdd | APIBreakingToRemove,
+  116)
+
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS
 #undef CONTEXTUAL_DECL_ATTR_ALIAS
diff --git a/include/swift/AST/Expr.h b/include/swift/AST/Expr.h
@@ -292,14 +292,18 @@ class alignas(8) Expr {
     Kind : 2
   );
 
-  SWIFT_INLINE_BITFIELD(ClosureExpr, AbstractClosureExpr, 1+1,
+  SWIFT_INLINE_BITFIELD(ClosureExpr, AbstractClosureExpr, 1+1+1,
     /// True if closure parameters were synthesized from anonymous closure
     /// variables.
     HasAnonymousClosureVars : 1,
 
     /// True if "self" can be captured implicitly without requiring "self."
     /// on each member reference.
-    ImplicitSelfCapture : 1
+    ImplicitSelfCapture : 1,
+
+    /// True if this @Sendable async closure parameter should implicitly
+    /// inherit the actor context from where it was formed.
+    InheritActorContext : 1
   );
 
   SWIFT_INLINE_BITFIELD_FULL(BindOptionalExpr, Expr, 16,
@@ -3876,6 +3880,7 @@ class ClosureExpr : public AbstractClosureExpr {
     setParameterList(params);
     Bits.ClosureExpr.HasAnonymousClosureVars = false;
     Bits.ClosureExpr.ImplicitSelfCapture = false;
+    Bits.ClosureExpr.InheritActorContext = false;
   }
 
   SourceRange getSourceRange() const;
@@ -3914,6 +3919,16 @@ class ClosureExpr : public AbstractClosureExpr {
     Bits.ClosureExpr.ImplicitSelfCapture = value;
   }
 
+  /// Whether this closure should implicitly inherit the actor context from
+  /// where it was formed. This only affects @Sendable async closures.
+  bool inheritsActorContext() const {
+    return Bits.ClosureExpr.InheritActorContext;
+  }
+
+  void setInheritsActorContext(bool value = true) {
+    Bits.ClosureExpr.InheritActorContext = value;
+  }
+
   /// Determine whether this closure expression has an
   /// explicitly-specified result type.
   bool hasExplicitResultType() const { return ArrowLoc.isValid(); }
diff --git a/include/swift/AST/Types.h b/include/swift/AST/Types.h
@@ -3383,6 +3383,7 @@ struct ParameterListInfo {
   SmallBitVector unsafeSendable;
   SmallBitVector unsafeMainActor;
   SmallBitVector implicitSelfCapture;
+  SmallBitVector inheritActorContext;
 
 public:
   ParameterListInfo() { }
@@ -3415,6 +3416,10 @@ struct ParameterListInfo {
   /// 'self' to be implicit, without requiring "self.".
   bool isImplicitSelfCapture(unsigned paramIdx) const;
 
+  /// Whether the given parameter is a closure that should inherit the
+  /// actor context from the context in which it was created.
+  bool inheritsActorContext(unsigned paramIdx) const;
+
   /// Whether there is any contextual information set on this parameter list.
   bool anyContextualInfo() const;
 
diff --git a/include/swift/Basic/Features.def b/include/swift/Basic/Features.def
@@ -46,5 +46,6 @@ LANGUAGE_FEATURE(Sendable, 0, "Sendable and @Sendable", true)
 LANGUAGE_FEATURE(BuiltinExecutor, 0, "Executor builtins", true)
 LANGUAGE_FEATURE(BuiltinContinuation, 0, "Continuation builtins", true)
 LANGUAGE_FEATURE(BuiltinTaskGroup, 0, "TaskGroup builtins", true)
+LANGUAGE_FEATURE(InheritActorContext, 0, "@_inheritActorContext attribute", true)
 
 #undef LANGUAGE_FEATURE
diff --git a/include/swift/Runtime/Concurrency.h b/include/swift/Runtime/Concurrency.h
@@ -584,6 +584,10 @@ SWIFT_EXPORT_FROM(swift_Concurrency) SWIFT_CC(swift)
 void swift_task_reportUnexpectedExecutor(
     const unsigned char *file, uintptr_t fileLength, bool fileIsASCII,
     uintptr_t line, ExecutorRef executor);
+
+SWIFT_EXPORT_FROM(swift_Concurrency) SWIFT_CC(swift)
+JobPriority swift_task_getCurrentThreadPriority(void);
+
 }
 
 #pragma clang diagnostic pop
diff --git a/lib/AST/ASTDumper.cpp b/lib/AST/ASTDumper.cpp
@@ -2548,6 +2548,8 @@ class PrintExpr : public ExprVisitor<PrintExpr> {
       PrintWithColorRAII(OS, ClosureModifierColor) << " single-expression";
     if (E->allowsImplicitSelfCapture())
       PrintWithColorRAII(OS, ClosureModifierColor) << " implicit-self";
+    if (E->inheritsActorContext())
+      PrintWithColorRAII(OS, ClosureModifierColor) << " inherits-actor-context";
 
     if (E->getParameters()) {
       OS << '\n';
diff --git a/lib/AST/ASTPrinter.cpp b/lib/AST/ASTPrinter.cpp
@@ -2782,6 +2782,17 @@ static bool usesFeatureBuiltinTaskGroup(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureInheritActorContext(Decl *decl) {
+  if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
+    for (auto param : *func->getParameters()) {
+      if (param->getAttrs().hasAttribute<InheritActorContextAttr>())
+        return true;
+    }
+  }
+
+  return false;
+}
+
 /// Determine the set of "new" features used on a given declaration.
 ///
 /// Note: right now, all features we check for are "new". At some point, we'll
diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
@@ -971,6 +971,7 @@ ParameterListInfo::ParameterListInfo(
   unsafeSendable.resize(params.size());
   unsafeMainActor.resize(params.size());
   implicitSelfCapture.resize(params.size());
+  inheritActorContext.resize(params.size());
 
   // No parameter owner means no parameter list means no default arguments
   // - hand back the zeroed bitvector.
@@ -1034,6 +1035,10 @@ ParameterListInfo::ParameterListInfo(
     if (param->getAttrs().hasAttribute<ImplicitSelfCaptureAttr>()) {
       implicitSelfCapture.set(i);
     }
+
+    if (param->getAttrs().hasAttribute<InheritActorContextAttr>()) {
+      inheritActorContext.set(i);
+    }
   }
 }
 
@@ -1070,9 +1075,15 @@ bool ParameterListInfo::isImplicitSelfCapture(unsigned paramIdx) const {
       : false;
 }
 
+bool ParameterListInfo::inheritsActorContext(unsigned paramIdx) const {
+  return paramIdx < inheritActorContext.size()
+      ? inheritActorContext[paramIdx]
+      : false;
+}
+
 bool ParameterListInfo::anyContextualInfo() const {
   return unsafeSendable.any() || unsafeMainActor.any() ||
-      implicitSelfCapture.any();
+      implicitSelfCapture.any() || inheritActorContext.any();
 }
 
 /// Turn a param list into a symbolic and printable representation that does not
diff --git a/lib/Sema/CSApply.cpp b/lib/Sema/CSApply.cpp
@@ -5712,17 +5712,25 @@ static bool hasCurriedSelf(ConstraintSystem &cs, ConcreteDeclRef callee,
 
 /// Apply the contextually Sendable flag to the given expression,
 static void applyContextualClosureFlags(
-      Expr *expr, bool sendable, bool forMainActor, bool implicitSelfCapture) {
+      Expr *expr, bool sendable, bool forMainActor, bool implicitSelfCapture,
+      bool inheritActorContext) {
   if (auto closure = dyn_cast<ClosureExpr>(expr)) {
     closure->setUnsafeConcurrent(sendable, forMainActor);
     closure->setAllowsImplicitSelfCapture(implicitSelfCapture);
+    closure->setInheritsActorContext(inheritActorContext);
     return;
   }
 
   if (auto captureList = dyn_cast<CaptureListExpr>(expr)) {
     applyContextualClosureFlags(
         captureList->getClosureBody(), sendable, forMainActor,
-        implicitSelfCapture);
+        implicitSelfCapture, inheritActorContext);
+  }
+
+  if (auto identity = dyn_cast<IdentityExpr>(expr)) {
+    applyContextualClosureFlags(
+        identity->getSubExpr(), sendable, forMainActor,
+        implicitSelfCapture, inheritActorContext);
   }
 }
 
@@ -5983,9 +5991,10 @@ Expr *ExprRewriter::coerceCallArguments(
     bool isMainActor = paramInfo.isUnsafeMainActor(paramIdx) ||
         (isUnsafeSendable && apply && isMainDispatchQueue(apply->getFn()));
     bool isImplicitSelfCapture = paramInfo.isImplicitSelfCapture(paramIdx);
+    bool inheritsActorContext = paramInfo.inheritsActorContext(paramIdx);
     applyContextualClosureFlags(
         arg, isUnsafeSendable && contextUsesConcurrencyFeatures(dc),
-        isMainActor, isImplicitSelfCapture);
+        isMainActor, isImplicitSelfCapture, inheritsActorContext);
 
     // If the types exactly match, this is easy.
     auto paramType = param.getOldType();
@@ -6138,6 +6147,20 @@ static bool isClosureLiteralExpr(Expr *expr) {
   return (isa<CaptureListExpr>(expr) || isa<ClosureExpr>(expr));
 }
 
+/// Whether we should propagate async down to a closure.
+static bool shouldPropagateAsyncToClosure(Expr *expr) {
+  if (auto IE = dyn_cast<IdentityExpr>(expr))
+    return shouldPropagateAsyncToClosure(IE->getSubExpr());
+
+  if (auto CLE = dyn_cast<CaptureListExpr>(expr))
+    return shouldPropagateAsyncToClosure(CLE->getClosureBody());
+
+  if (auto CE = dyn_cast<ClosureExpr>(expr))
+    return CE->inheritsActorContext();
+
+  return false;
+}
+
 /// If the expression is an explicit closure expression (potentially wrapped in
 /// IdentityExprs), change the type of the closure and identities to the
 /// specified type and return true.  Otherwise, return false with no effect.
@@ -7002,8 +7025,8 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
       }
     }
 
-    // If we have a ClosureExpr, then we can safely propagate the 'concurrent'
-    // bit to the closure without invalidating prior analysis.
+    // If we have a ClosureExpr, then we can safely propagate @Sendable
+    // to the closure without invalidating prior analysis.
     auto fromEI = fromFunc->getExtInfo();
     if (toEI.isSendable() && !fromEI.isSendable()) {
       auto newFromFuncType = fromFunc->withExtInfo(fromEI.withConcurrent());
@@ -7017,6 +7040,22 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
       }
     }
 
+    // If we have a ClosureExpr, then we can safely propagate the 'async'
+    // bit to the closure without invalidating prior analysis.
+    fromEI = fromFunc->getExtInfo();
+    if (toEI.isAsync() && !fromEI.isAsync() &&
+        shouldPropagateAsyncToClosure(expr)) {
+      auto newFromFuncType = fromFunc->withExtInfo(fromEI.withAsync());
+      if (applyTypeToClosureExpr(cs, expr, newFromFuncType)) {
+        fromFunc = newFromFuncType->castTo<FunctionType>();
+
+        // Propagating the 'concurrent' bit might have satisfied the entire
+        // conversion. If so, we're done, otherwise keep converting.
+        if (fromFunc->isEqual(toType))
+          return expr;
+      }
+    }
+
     // If we have a ClosureExpr, then we can safely propagate a global actor
     // to the closure without invalidating prior analysis.
     fromEI = fromFunc->getExtInfo();
diff --git a/lib/Sema/TypeCheckAttr.cpp b/lib/Sema/TypeCheckAttr.cpp
@@ -138,6 +138,7 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
   IGNORED_ATTR(UnsafeSendable)
   IGNORED_ATTR(UnsafeMainActor)
   IGNORED_ATTR(ImplicitSelfCapture)
+  IGNORED_ATTR(InheritActorContext)
 #undef IGNORED_ATTR
 
   void visitAlignmentAttr(AlignmentAttr *attr) {
diff --git a/lib/Sema/TypeCheckConcurrency.cpp b/lib/Sema/TypeCheckConcurrency.cpp
@@ -773,19 +773,26 @@ static bool isAsyncCall(const ApplyExpr *call) {
 /// features.
 static bool shouldDiagnoseExistingDataRaces(const DeclContext *dc);
 
-/// Determine whether this closure is escaping.
-static bool isSendableClosure(const AbstractClosureExpr *closure) {
+/// Determine whether this closure should be treated as Sendable.
+///
+/// \param forActorIsolation Whether this check is for the purposes of
+/// determining whether the closure must be non-isolated.
+static bool isSendableClosure(
+    const AbstractClosureExpr *closure, bool forActorIsolation) {
+  if (auto explicitClosure = dyn_cast<ClosureExpr>(closure)) {
+    if (forActorIsolation && explicitClosure->inheritsActorContext())
+      return false;
+
+    if (explicitClosure->isUnsafeSendable())
+      return true;
+  }
+
   if (auto type = closure->getType()) {
     if (auto fnType = type->getAs<AnyFunctionType>())
       if (fnType->isSendable())
         return true;
   }
 
-  if (auto explicitClosure = dyn_cast<ClosureExpr>(closure)) {
-    if (explicitClosure->isUnsafeSendable())
-      return true;
-  }
-
   return false;
 }
 
@@ -2113,7 +2120,7 @@ namespace {
       }
 
       if (auto closure = dyn_cast<AbstractClosureExpr>(dc)) {
-        if (isSendableClosure(closure)) {
+        if (isSendableClosure(closure, /*forActorIsolation=*/true)) {
           return diag::actor_isolated_from_concurrent_closure;
         }
 
@@ -2310,8 +2317,9 @@ namespace {
         }
       }
 
-      // Sendable closures are always actor-independent.
-      if (isSendableClosure(closure))
+      // Sendable closures are actor-independent unless the closure has
+      // specifically opted into inheriting actor isolation.
+      if (isSendableClosure(closure, /*forActorIsolation=*/true))
         return ClosureActorIsolation::forIndependent();
 
       // A non-escaping closure gets its isolation from its context.
@@ -2362,7 +2370,7 @@ bool ActorIsolationChecker::mayExecuteConcurrentlyWith(
   while (useContext != defContext) {
     // If we find a concurrent closure... it can be run concurrently.
     if (auto closure = dyn_cast<AbstractClosureExpr>(useContext)) {
-      if (isSendableClosure(closure))
+      if (isSendableClosure(closure, /*forActorIsolation=*/false))
         return true;
     }
 
diff --git a/lib/Sema/TypeCheckDeclOverride.cpp b/lib/Sema/TypeCheckDeclOverride.cpp
@@ -1547,6 +1547,7 @@ namespace  {
     UNINTERESTING_ATTR(UnsafeSendable)
     UNINTERESTING_ATTR(UnsafeMainActor)
     UNINTERESTING_ATTR(ImplicitSelfCapture)
+    UNINTERESTING_ATTR(InheritActorContext)
 #undef UNINTERESTING_ATTR
 
     void visitAvailableAttr(AvailableAttr *attr) {
diff --git a/stdlib/public/Concurrency/Actor.cpp b/stdlib/public/Concurrency/Actor.cpp
@@ -27,6 +27,7 @@
 #include "swift/ABI/Actor.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "TaskPrivate.h"
+#include <dispatch/dispatch.h>
 
 #if defined(__APPLE__)
 #include <asl.h>
@@ -259,6 +260,17 @@ static bool isExecutingOnMainThread() {
 #endif
 }
 
+JobPriority swift::swift_task_getCurrentThreadPriority() {
+  if (isExecutingOnMainThread())
+    return JobPriority::UserInitiated;
+
+#if defined(__APPLE__)
+  return static_cast<JobPriority>(qos_class_self());
+#else
+  return JobPriority::Unspecified;
+#endif
+}
+
 SWIFT_CC(swift)
 static bool swift_task_isCurrentExecutorImpl(ExecutorRef executor) {
   if (auto currentTracking = ExecutorTrackingInfo::current()) {
diff --git a/stdlib/public/Concurrency/Task.swift b/stdlib/public/Concurrency/Task.swift
diff --git a/test/Concurrency/Runtime/async.swift b/test/Concurrency/Runtime/async.swift
diff --git a/test/Concurrency/actor_isolation.swift b/test/Concurrency/actor_isolation.swift
diff --git a/test/Concurrency/global_actor_inference.swift b/test/Concurrency/global_actor_inference.swift
diff --git a/test/ModuleInterface/features.swift b/test/ModuleInterface/features.swift
diff --git a/test/SILGen/hop_to_executor.swift b/test/SILGen/hop_to_executor.swift
