Merge main 2022-05-27

CHANGELOG.md

@@ -5,6 +5,83 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
 
 ## Swift 5.7
 
+* [SE-0338][]:
+
+  Non-isolated async functions now always execute on the global concurrent pool,
+  so calling a non-isolated async function from actor-isolated code will leave
+  the actor. For example:
+
+  ```swift
+  class C { }
+
+  func f(_: C) async { /* always executes on the global concurrent pool */ }
+
+  actor A {
+    func g(c: C) async {
+      /* always executes on the actor */
+      print("on the actor")
+
+      await f(c)
+    }
+  }
+  ```
+
+  Prior to this change, the call from `f` to `g` might have started execution of
+  `g` on the actor, which could lead to actors being busy longer than strictly
+  necessary. Now, the non-isolated async function will always hop to the global
+  cooperative pool, not run on the actor. This can result in a behavior change
+  for programs that assumed that a non-isolated async function called from a
+  `@MainActor` context will be executed on the main actor, although such
+  programs were already technically incorrect.
+
+  Additionally, when leaving an actor to execution on the global cooperative
+  pool, `Sendable` checking will be performed, so the compiler will emit a
+  diagnostic in the call to `f` if `c` is not of `Sendable` type.
+
+* [SE-0350][]:
+
+  The standard library has a new `Regex<Output>` type.
+
+  This type represents an _extended regular expression_, allowing more fluent
+  string processing operations. A `Regex` may be created by
+  [initialization from a string][SE-0355]:
+  ```
+  let pattern = "a[bc]+" // matches "a" followed by one or more instances
+                         // of either "b" or "c"
+  let regex = try! Regex(pattern)
+  ```
+  Or via a [regex literal][SE-0354]:
+  ```
+  let regex = #/a[bc]+/#
+  ```
+  In Swift 6, `/` will also be supported as a delimiter for `Regex` literals.
+  You can enable this mode in Swift 5.7 with the `-enable-bare-slash-regex`
+  flag. Doing so will cause some existing expressions that use `/` as an 
+  operator to no longer compile; you can add parentheses or line breaks as a
+  workaround.
+
+  There are [new string-processing algorithms][SE-0357] that support
+  `String`, `Regex` and arbitrary `Collection` types.
+
+* [SE-0329][]:
+  New types representing time and clocks were introduced. This includes a protocol `Clock` defining clocks which allow for defining a concept of now and a way to wake up after a given instant. Additionally a new protocol `InstantProtocol` for defining instants in time was added. Furthermore a new protocol `DurationProtocol` was added to define an elapsed duration between two given `InstantProtocol` types. Most commonly the `Clock` types for general use are the `SuspendingClock` and `ContinuousClock` which represent the most fundamental clocks for the system. The `SuspendingClock` type does not progress while the machine is suspended whereas the `ContinuousClock` progresses no matter the state of the machine. 
+
+  ```swift
+    func delayedHello() async throws {
+      try await Task.sleep(until: .now + .milliseconds(123), clock: .continuous)
+      print("hello delayed world")
+    }
+  ```
+
+  `Clock` also has methods to measure the elapsed duration of the execution of work. In the case of the `SuspendingClock` and `ContinuousClock` this measures with high resolution and is suitable for benchmarks.
+
+  ```swift
+  let clock = ContinuousClock()
+  let elapsed = clock.measure {
+    someLongRunningWork()
+  }
+  ```
+
 * [SE-0309][]:
 
   Protocols with associated types and `Self` requirements can now be used as the
@@ -72,10 +149,26 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
 
 * [SE-0353][]:
 
-  Further generalizing the above, protocol-constrained types can also be used with `any`:
+  Protocols with primary associated types can now be used in existential types,
+  enabling same-type constraints on those associated types.
+
+  ```
+  let strings: any Collection<String> = [ "Hello" ]
+  ```
+
+  Note that language features requiring runtime support like dynamic casts
+  (`is`, `as?`, `as!`), as well as generic usages of parameterized existentials
+  in generic types (e.g. `Array<any Collection<Int>>`) involve additional
+  availability checks to use. Back-deploying usages in generic position can be
+  worked around with a generic type-erasing wrapper struct, which is now much
+  simpler to implement:
 
   ```swift
-    func findBestGraph(_: [any Graph<Int>]) -> any Graph<Int> {...}
+  struct AnyCollection<T> {
+    var wrapped: any Collection<T>
+  }
+
+  let arrayOfCollections: [AnyCollection<T>] = [ /**/ ]
   ```
 
 * [SE-0358][]:
@@ -9354,21 +9447,27 @@ Swift 1.0
 [SE-0326]: <https://github.com/apple/swift-evolution/blob/main/proposals/0326-extending-multi-statement-closure-inference.md>
 [SE-0327]: <https://github.com/apple/swift-evolution/blob/main/proposals/0327-actor-initializers.md>
 [SE-0328]: <https://github.com/apple/swift-evolution/blob/main/proposals/0328-structural-opaque-result-types.md>
+[SE-0329]: <https://github.com/apple/swift-evolution/blob/main/proposals/0329-clock-instant-duration.md>
 [SE-0331]: <https://github.com/apple/swift-evolution/blob/main/proposals/0331-remove-sendable-from-unsafepointer.md>
 [SE-0333]: <https://github.com/apple/swift-evolution/blob/main/proposals/0333-with-memory-rebound.md>
 [SE-0334]: <https://github.com/apple/swift-evolution/blob/main/proposals/0334-pointer-usability-improvements.md>
 [SE-0335]: <https://github.com/apple/swift-evolution/blob/main/proposals/0335-existential-any.md>
 [SE-0336]: <https://github.com/apple/swift-evolution/blob/main/proposals/0336-distributed-actor-isolation.md>
 [SE-0337]: <https://github.com/apple/swift-evolution/blob/main/proposals/0337-support-incremental-migration-to-concurrency-checking.md>
+[SE-0338]: <https://github.com/apple/swift-evolution/blob/main/proposals/0338-clarify-execution-non-actor-async.md>
 [SE-0340]: <https://github.com/apple/swift-evolution/blob/main/proposals/0340-swift-noasync.md>
 [SE-0341]: <https://github.com/apple/swift-evolution/blob/main/proposals/0341-opaque-parameters.md>
 [SE-0343]: <https://github.com/apple/swift-evolution/blob/main/proposals/0343-top-level-concurrency.md>
 [SE-0345]: <https://github.com/apple/swift-evolution/blob/main/proposals/0345-if-let-shorthand.md>
 [SE-0346]: <https://github.com/apple/swift-evolution/blob/main/proposals/0346-light-weight-same-type-syntax.md>
 [SE-0347]: <https://github.com/apple/swift-evolution/blob/main/proposals/0347-type-inference-from-default-exprs.md>
 [SE-0349]: <https://github.com/apple/swift-evolution/blob/main/proposals/0349-unaligned-loads-and-stores.md>
+[SE-0350]: <https://github.com/apple/swift-evolution/blob/main/proposals/0350-regex-type-overview.md>
 [SE-0352]: <https://github.com/apple/swift-evolution/blob/main/proposals/0352-implicit-open-existentials.md>
 [SE-0353]: <https://github.com/apple/swift-evolution/blob/main/proposals/0353-constrained-existential-types.md>
+[SE-0354]: <https://github.com/apple/swift-evolution/blob/main/proposals/0354-regex-literals.md>
+[SE-0355]: <https://github.com/apple/swift-evolution/blob/main/proposals/0355-regex-syntax-run-time-construction.md>
+[SE-0357]: <https://github.com/apple/swift-evolution/blob/main/proposals/0357-regex-string-processing-algorithms.md>
 [SE-0358]: <https://github.com/apple/swift-evolution/blob/main/proposals/0358-primary-associated-types-in-stdlib.md>
 
 [SR-75]: <https://bugs.swift.org/browse/SR-75>

include/swift/AST/Availability.h

@@ -93,6 +93,18 @@ class VersionRange {
     return getLowerEndpoint() >= Other.getLowerEndpoint();
   }
 
+  // Returns true if all the versions in the Other range are versions in this
+  // range and the ranges are not equal.
+  bool isSupersetOf(const VersionRange &Other) const {
+    if (isEmpty() || Other.isAll())
+      return false;
+
+    if (isAll() || Other.isEmpty())
+      return true;
+
+    return getLowerEndpoint() < Other.getLowerEndpoint();
+  }
+
   /// Mutates this range to be a best-effort underapproximation of
   /// the intersection of itself and Other. This is the
   /// meet operation (greatest lower bound) in the version range lattice.
@@ -244,10 +256,17 @@ class AvailabilityContext {
   /// Returns true if \p other makes stronger guarantees than this context.
   ///
   /// That is, `a.isContainedIn(b)` implies `a.union(b) == b`.
-  bool isContainedIn(AvailabilityContext other) const {
+  bool isContainedIn(const AvailabilityContext &other) const {
     return OSVersion.isContainedIn(other.OSVersion);
   }
 
+  /// Returns true if \p other is a strict subset of this context.
+  ///
+  /// That is, `a.isSupersetOf(b)` implies `a != b` and `a.union(b) == a`.
+  bool isSupersetOf(const AvailabilityContext &other) const {
+    return OSVersion.isSupersetOf(other.OSVersion);
+  }
+
   /// Returns true if this context has constraints that make it impossible to
   /// actually occur.
   ///
@@ -272,7 +291,7 @@ class AvailabilityContext {
   ///
   /// As an example, this is used when figuring out the required availability
   /// for a type that references multiple nominal decls.
-  void intersectWith(AvailabilityContext other) {
+  void intersectWith(const AvailabilityContext &other) {
     OSVersion.intersectWith(other.getOSVersion());
   }
 
@@ -283,7 +302,7 @@ class AvailabilityContext {
   /// treating some invalid deployment environments as available.
   ///
   /// As an example, this is used for the true branch of `#available`.
-  void constrainWith(AvailabilityContext other) {
+  void constrainWith(const AvailabilityContext &other) {
     OSVersion.constrainWith(other.getOSVersion());
   }
 
@@ -295,7 +314,7 @@ class AvailabilityContext {
   ///
   /// As an example, this is used for the else branch of a conditional with
   /// multiple `#available` checks.
-  void unionWith(AvailabilityContext other) {
+  void unionWith(const AvailabilityContext &other) {
     OSVersion.unionWith(other.getOSVersion());
   }
 

include/swift/AST/DiagnosticsParse.def

@@ -1816,7 +1816,10 @@ ERROR(version_component_not_number,none,
 ERROR(compiler_version_too_many_components,none,
       "compiler version must not have more than five components", ())
 WARNING(unused_compiler_version_component,NoUsage,
-      "the second version component is not used for comparison", ())
+      "the second version component is not used for comparison in legacy "
+      "compiler versions%select{|; are you trying to encode a new Swift "
+      "compiler version for compatibility with legacy compilers?}0",
+      (bool))
 ERROR(empty_version_component,none,
       "found empty version component", ())
 ERROR(compiler_version_component_out_of_range,none,

include/swift/AST/DiagnosticsSema.def

@@ -1965,6 +1965,9 @@ NOTE(non_sendable_nominal,none,
 NOTE(add_nominal_sendable_conformance,none,
      "consider making %0 %1 conform to the 'Sendable' protocol",
      (DescriptiveDeclKind, DeclName))
+NOTE(add_generic_parameter_sendable_conformance,none,
+     "consider making generic parameter %0 conform to the 'Sendable' protocol",
+     (Type))
 REMARK(add_predates_concurrency_import,none,
      "add '@preconcurrency' to %select{suppress|treat}0 "
      "'Sendable'-related %select{warnings|errors}0 from module %1"
@@ -4570,6 +4573,12 @@ ERROR(concurrent_access_of_inout_param,none,
 ERROR(non_sendable_capture,none,
       "capture of %1 with non-sendable type %0 in a `@Sendable` closure",
       (Type, DeclName))
+ERROR(implicit_async_let_non_sendable_capture,none,
+      "capture of %1 with non-sendable type %0 in 'async let' binding",
+      (Type, DeclName))
+ERROR(implicit_non_sendable_capture,none,
+      "implicit capture of %1 requires that %0 conforms to `Sendable`",
+      (Type, DeclName))
 
 NOTE(actor_isolated_sync_func,none,
      "calls to %0 %1 from outside of its actor context are "
@@ -4648,9 +4657,10 @@ ERROR(isolated_parameter_not_actor,none,
 
 WARNING(non_sendable_param_type,none,
         "non-sendable type %0 %select{passed in call to %4 %2 %3|"
+        "exiting %4 context in call to non-isolated %2 %3|"
         "passed in implicitly asynchronous call to %4 %2 %3|"
-        "in parameter of %4 %2 %3 satisfying non-isolated protocol "
-        "requirement|"
+        "in parameter of %4 %2 %3 satisfying protocol requirement|"
+        "in parameter of %4 overriding %2 %3|"
         "in parameter of %4 '@objc' %2 %3}1 cannot cross actor boundary",
         (Type, unsigned, DescriptiveDeclKind, DeclName, ActorIsolation))
 WARNING(non_sendable_call_param_type,none,
@@ -4659,8 +4669,10 @@ WARNING(non_sendable_call_param_type,none,
         (Type, bool, ActorIsolation))
 WARNING(non_sendable_result_type,none,
         "non-sendable type %0 returned by %select{call to %4 %2 %3|"
+        "call from %4 context to non-isolated %2 %3|"
         "implicitly asynchronous call to %4 %2 %3|"
-        "%4 %2 %3 satisfying non-isolated protocol requirement|"
+        "%4 %2 %3 satisfying protocol requirement|"
+        "%4 overriding %2 %3|"
         "%4 '@objc' %2 %3}1 cannot cross actor boundary",
         (Type, unsigned, DescriptiveDeclKind, DeclName, ActorIsolation))
 WARNING(non_sendable_call_result_type,none,
@@ -4670,8 +4682,10 @@ WARNING(non_sendable_call_result_type,none,
 WARNING(non_sendable_property_type,none,
         "non-sendable type %0 in %select{"
         "%select{asynchronous access to %5 %1 %2|"
+        "asynchronous access from %5 context to non-isolated %1 %2|"
         "implicitly asynchronous access to %5 %1 %2|"
-        "conformance of %5 %1 %2 to non-isolated protocol requirement|"
+        "conformance of %5 %1 %2 to protocol requirement|"
+        "%5 overriding %1 %2|"
         "%5 '@objc' %1 %2}4|captured local %1 %2}3 cannot "
         "cross %select{actor|task}3 boundary",
         (Type, DescriptiveDeclKind, DeclName, bool, unsigned, ActorIsolation))

include/swift/AST/PrintOptions.h

@@ -285,6 +285,9 @@ struct PrintOptions {
   /// types.
   bool PrintExplicitAny = false;
 
+  /// Whether to desugar the constraint for an existential type.
+  bool DesugarExistentialConstraint = false;
+
   /// Whether to skip keywords with a prefix of underscore such as __consuming.
   bool SkipUnderscoredKeywords = false;
 

include/swift/AST/TypeRefinementContext.h

@@ -54,15 +54,19 @@ class TypeRefinementContext : public ASTAllocated<TypeRefinementContext> {
     /// The root refinement context.
     Root,
 
-    /// The context was introduced by a declaration (e.g., the body of a
-    /// function declaration or the contents of a class declaration).
+    /// The context was introduced by a declaration with an explicit
+    /// availability attribute. The context contains both the signature and the
+    /// body of the declaration.
     Decl,
 
-    /// The context was introduced by an API boundary; that is, we are in
-    /// a module with library evolution enabled and the parent context's
-    /// contents can be visible to the module's clients, but this context's
-    /// contents are not.
-    APIBoundary,
+    /// The context was introduced implicitly by a declaration. The context may
+    /// cover the entire declaration or it may cover a subset of it. For
+    /// example, a public, non-inlinable function declaration in an API module
+    /// will have at least two associated contexts: one for the entire
+    /// declaration at the declared availability of the API and a nested
+    /// implicit context for the body of the function, which will always run at
+    /// the deployment target of the library.
+    DeclImplicit,
 
     /// The context was introduced for the Then branch of an IfStmt.
     IfStmtThenBranch,
@@ -131,7 +135,8 @@ class TypeRefinementContext : public ASTAllocated<TypeRefinementContext> {
     }
 
     Decl *getAsDecl() const {
-      assert(IntroReason == Reason::Decl || IntroReason == Reason::APIBoundary);
+      assert(IntroReason == Reason::Decl ||
+             IntroReason == Reason::DeclImplicit);
       return D;
     }
 
@@ -163,8 +168,8 @@ class TypeRefinementContext : public ASTAllocated<TypeRefinementContext> {
 
   SourceRange SrcRange;
 
-  /// A canonical availability info for this context, computed top-down from the root
-  /// context (compilation deployment target).
+  /// A canonical availability info for this context, computed top-down from the
+  /// root context.
   AvailabilityContext AvailabilityInfo;
 
   /// If this context was annotated with an availability attribute, this property captures that.
@@ -194,8 +199,8 @@ class TypeRefinementContext : public ASTAllocated<TypeRefinementContext> {
 
   /// Create a refinement context for the given declaration.
   static TypeRefinementContext *
-  createForAPIBoundary(ASTContext &Ctx, Decl *D, TypeRefinementContext *Parent,
-                       const AvailabilityContext &Info, SourceRange SrcRange);
+  createForDeclImplicit(ASTContext &Ctx, Decl *D, TypeRefinementContext *Parent,
+                        const AvailabilityContext &Info, SourceRange SrcRange);
 
   /// Create a refinement context for the Then branch of the given IfStmt.
   static TypeRefinementContext *

include/swift/Basic/LangOptions.h

@@ -326,10 +326,6 @@ namespace swift {
     /// in calls to generic functions.
     bool EnableOpenedExistentialTypes = false;
 
-    /// Enable support for parameterized protocol types in existential
-    /// position.
-    bool EnableParameterizedExistentialTypes = false;
-
     /// Enable experimental flow-sensitive concurrent captures.
     bool EnableExperimentalFlowSensitiveConcurrentCaptures = false;
 

include/swift/Basic/Version.h

@@ -129,7 +129,12 @@ class Version {
   /// Return this Version struct as the appropriate version string for APINotes.
   std::string asAPINotesVersionString() const;
 
-  /// Parse a version in the form used by the _compiler_version \#if condition.
+  /// Parse a version in the form used by the _compiler_version(string-literal)
+  /// \#if condition.
+  ///
+  /// \note This is \em only used for the string literal version, so it includes
+  /// backwards-compatibility logic to convert it to something that can be
+  /// compared with a modern SWIFT_COMPILER_VERSION.
   static Optional<Version> parseCompilerVersionString(StringRef VersionString,
                                                       SourceLoc Loc,
                                                       DiagnosticEngine *Diags);

include/swift/Option/FrontendOptions.td

@@ -543,10 +543,6 @@ def enable_explicit_existential_types :
   Flag<["-"], "enable-explicit-existential-types">,
   HelpText<"Enable experimental support for explicit existential types">;
 
-def enable_parameterized_existential_types :
-  Flag<["-"], "enable-parameterized-existential-types">,
-  HelpText<"Enable experimental support for parameterized existential types">;
-
 def enable_experimental_opened_existential_types :
   Flag<["-"], "enable-experimental-opened-existential-types">,
   HelpText<"Enable experimental support for implicitly opened existentials">;

include/swift/SILOptimizer/Analysis/Reachability.h

@@ -149,7 +149,7 @@ class BackwardReachability {
 ///     Effect effectForPhi(SILBasicBlock *);
 ///
 ///     /// The uses from which reachability will begin.
-///     ArrayRef<SILInstruction *> gens();
+///     iterable gens();
 /// }
 template <typename Effects>
 class IterativeBackwardReachability final {