swiftlang · CodaFi · May 26, 2022 · May 25, 2022 · May 25, 2022 · May 25, 2022
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,9 +5,42 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
 
 ## Swift 5.7
 
+* [SE-0353][]:
+
+  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
+  struct AnyCollection<T> {
+    var wrapped: any Collection<T>
+  }
+
+  let arrayOfCollections: [AnyCollection<T>] = [ /**/ ]
+  ```
+
 * [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. 
 
+* [SE-0309][]:
+
+  Protocols with associated types and `Self` requirements can now be used as the
+  types of values with the `any` keyword.
+
+  Protocol methods that return associated types can be called on an `any` type;
+  the result is type-erased to the associated type's upper bound, which is another
+  `any` type having the same constraints as the associated type. For example:
+
   ```swift
     func delayedHello() async throws {
       try await Task.sleep(until: .now + .milliseconds(123), clock: .continuous)

diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
@@ -338,10 +338,6 @@ 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;
 

diff --git a/include/swift/Option/FrontendOptions.td b/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">;

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
@@ -448,9 +448,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableExperimentalNamedOpaqueTypes |=
       Args.hasArg(OPT_enable_experimental_named_opaque_types);
 
-  Opts.EnableParameterizedExistentialTypes |=
-      Args.hasArg(OPT_enable_parameterized_existential_types);
-
   Opts.EnableOpenedExistentialTypes =
     Args.hasFlag(OPT_enable_experimental_opened_existential_types,
                  OPT_disable_experimental_opened_existential_types,

diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
@@ -632,7 +632,7 @@ static Type applyGenericArguments(Type type, TypeResolution resolution,
     // Build ParameterizedProtocolType if the protocol has a primary associated
     // type and we're in a supported context (for now just generic requirements,
     // inheritance clause, extension binding).
-    if (!resolution.getOptions().isParameterizedProtocolSupported(ctx.LangOpts)) {
+    if (!resolution.getOptions().isParameterizedProtocolSupported()) {
       diags.diagnose(loc, diag::parameterized_protocol_not_supported);
       return ErrorType::get(ctx);
     }

diff --git a/lib/Sema/TypeCheckType.h b/lib/Sema/TypeCheckType.h
@@ -284,18 +284,14 @@ class TypeResolutionOptions {
   }
 
   /// Whether parameterized protocol types are supported in this context.
-  ///
-  /// FIXME: Remove LangOptions parameter once EnableParameterizedExistentialTypes
-  /// staging flag is gone.
-  bool isParameterizedProtocolSupported(const LangOptions &opts) const {
+  bool isParameterizedProtocolSupported() const {
     switch (context) {
     case Context::Inherited:
     case Context::ExtensionBinding:
     case Context::GenericRequirement:
-      return true;
     case Context::ExistentialConstraint:
     case Context::MetatypeBase:
-      return opts.EnableParameterizedExistentialTypes;
+      return true;
     case Context::None:
     case Context::TypeAliasDecl:
     case Context::GenericTypeAliasDecl:

diff --git a/test/Constraints/existential_metatypes.swift b/test/Constraints/existential_metatypes.swift
@@ -90,3 +90,33 @@ func testP3(_ p: P3, something: Something) {
 func testIUOToAny(_ t: AnyObject.Type!) {
   let _: Any = t
 }
+
+protocol P4<T> {
+  associatedtype T
+}
+
+protocol Q4<T> {
+  associatedtype T
+}
+
+protocol PP4<U>: P4<Self.U.T> {
+  associatedtype U: P4<U>
+}
+
+func parameterizedExistentials() {
+  var qp: (any Q4<Int>).Type
+  var pp: (any P4<Int>).Type = qp // expected-error{{cannot convert value of type '(any Q4<Int>).Type' to specified type '(any P4<Int>).Type'}}
+
+  var qt: any Q4<Int>.Type
+  qt = qp // expected-error{{cannot assign value of type '(any Q4<Int>).Type' to type 'any Q4<Int>.Type'}}
+  qp = qt // expected-error{{cannot assign value of type 'any Q4<Int>.Type' to type '(any Q4<Int>).Type'}}
+  var pt: any P4<Int>.Type = qt // expected-error{{cannot convert value of type 'any Q4<Int>.Type' to specified type 'any P4<Int>.Type'}}
+  pt = pp // expected-error{{cannot assign value of type '(any P4<Int>).Type' to type 'any P4<Int>.Type'}}
+  pp = pt // expected-error{{cannot assign value of type 'any P4<Int>.Type' to type '(any P4<Int>).Type'}}
+
+  var ppp: (any PP4<Int>).Type
+  pp = ppp // expected-error{{cannot assign value of type '(any PP4<Int>).Type' to type '(any P4<Int>).Type'}}
+
+  var ppt: any PP4<Int>.Type
+  pt = ppt
+}
diff --git a/test/Constraints/parameterized_existential_metatypes.swift b/test/Constraints/parameterized_existential_metatypes.swift
diff --git a/test/IRGen/existential_shape_metadata.swift b/test/IRGen/existential_shape_metadata.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -emit-ir %s -swift-version 5  -disable-availability-checking -enable-parameterized-existential-types | %IRGenFileCheck %s
+// RUN: %target-swift-frontend -emit-ir %s -swift-version 5 -disable-availability-checking | %IRGenFileCheck %s
 
 // CHECK-LABEL: @"$sl26existential_shape_metadata2Q0_pyxXPXGMq" = linkonce_odr hidden constant
 // CHECK-SAME:  { i32 {{.*}}sub ([[INT]] ptrtoint (i8** @{{[0-9]+}} to [[INT]])

diff --git a/test/Interpreter/parameterized_existentials.swift b/test/Interpreter/parameterized_existentials.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-Xfrontend -enable-parameterized-existential-types -Xfrontend -disable-availability-checking)
+// RUN: %target-run-simple-swift(-Xfrontend -disable-availability-checking)
 // REQUIRES: executable_test
 
 import StdlibUnittest

diff --git a/test/RemoteAST/parameterized_existentials.swift b/test/RemoteAST/parameterized_existentials.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-remoteast-test -enable-parameterized-existential-types -disable-availability-checking %s | %FileCheck %s
+// RUN: %target-swift-remoteast-test -disable-availability-checking %s | %FileCheck %s
 
 // REQUIRES: swift-remoteast-test
 

diff --git a/test/SILGen/parameterized_existentials.swift b/test/SILGen/parameterized_existentials.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-silgen -module-name parameterized -enable-parameterized-existential-types -disable-availability-checking %s | %FileCheck %s
+// RUN: %target-swift-emit-silgen -module-name parameterized -disable-availability-checking %s | %FileCheck %s
 
 protocol P<T, U, V> {
   associatedtype T

diff --git a/test/SILOptimizer/cast_folding_parameterized_protocol.swift b/test/SILOptimizer/cast_folding_parameterized_protocol.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend %s -emit-sil -enable-parameterized-existential-types -disable-availability-checking -O -o - | %FileCheck %s
+// RUN: %target-swift-frontend %s -emit-sil -disable-availability-checking -O -o - | %FileCheck %s
 
 public protocol P<T> {
   associatedtype T

diff --git a/test/Sema/availability_parameterized_existential.swift b/test/Sema/availability_parameterized_existential.swift
@@ -1,8 +1,8 @@
-// RUN: %target-typecheck-verify-swift -target %target-cpu-apple-macosx10.50 -disable-objc-attr-requires-foundation-module -enable-parameterized-existential-types
-// RUN: not %target-swift-frontend -target %target-cpu-apple-macosx10.50 -disable-objc-attr-requires-foundation-module -enable-parameterized-existential-types -typecheck %s 2>&1 | %FileCheck %s '--implicit-check-not=<unknown>:0'
+// RUN: %target-typecheck-verify-swift -target %target-cpu-apple-macosx10.50 -disable-objc-attr-requires-foundation-module
+// RUN: not %target-swift-frontend -target %target-cpu-apple-macosx10.50 -disable-objc-attr-requires-foundation-module -typecheck %s 2>&1 | %FileCheck %s '--implicit-check-not=<unknown>:0'
 
 // Make sure we do not emit availability errors or warnings when -disable-availability-checking is passed
-// RUN: not %target-swift-frontend -target %target-cpu-apple-macosx10.50 -typecheck -disable-objc-attr-requires-foundation-module -enable-parameterized-existential-types -disable-availability-checking %s 2>&1 | %FileCheck %s '--implicit-check-not=error:'
+// RUN: not %target-swift-frontend -target %target-cpu-apple-macosx10.50 -typecheck -disable-objc-attr-requires-foundation-module -disable-availability-checking %s 2>&1 | %FileCheck %s '--implicit-check-not=error:'
 
 // REQUIRES: OS=macosx
 

diff --git a/test/Serialization/parameterized_protocol.swift b/test/Serialization/parameterized_protocol.swift
@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -enable-parameterized-existential-types -emit-module %S/Inputs/parameterized_protocol_other.swift -emit-module-path %t/parameterized_protocol_other.swiftmodule
-// RUN: %target-typecheck-verify-swift -enable-parameterized-existential-types -I%t
+// RUN: %target-swift-frontend -emit-module %S/Inputs/parameterized_protocol_other.swift -emit-module-path %t/parameterized_protocol_other.swiftmodule
+// RUN: %target-typecheck-verify-swift -I%t
 
 import parameterized_protocol_other
 

diff --git a/test/type/opaque_parameterized_existential.swift b/test/type/opaque_parameterized_existential.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -enable-parameterized-existential-types -disable-availability-checking -typecheck -verify %s
+// RUN: %target-swift-frontend -disable-availability-checking -typecheck -verify %s
 
 // I do not like nested some type params,
 // I do not like them Σam-i-am

diff --git a/test/type/parameterized_existential.swift b/test/type/parameterized_existential.swift
@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on -disable-availability-checking -enable-parameterized-existential-types
+// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on -disable-availability-checking
 
 protocol Sequence<Element> {
   associatedtype Element

diff --git a/test/type/parameterized_protocol.swift b/test/type/parameterized_protocol.swift
@@ -29,7 +29,7 @@ protocol Invalid5<Element, Element> {
 
 /// Test semantics
 
-protocol Sequence<Element> {
+protocol Sequence<Element> { // expected-note {{'Sequence' declared here}}
   associatedtype Element
   // expected-note@-1 {{protocol requires nested type 'Element'; do you want to add it?}}
 }
@@ -189,17 +189,17 @@ func returnsSequenceOfInt1() -> Sequence<Int> {}
 // expected-error@-1 {{protocol type with type arguments can only be used as a generic constraint}}
 
 func takesSequenceOfInt2(_: any Sequence<Int>) {}
-// expected-error@-1 {{protocol type with type arguments can only be used as a generic constraint}}
 
 func returnsSequenceOfInt2() -> any Sequence<Int> {}
-// expected-error@-1 {{protocol type with type arguments can only be used as a generic constraint}}
 
 func typeExpr() {
   _ = Sequence<Int>.self
   // expected-error@-1 {{protocol type with type arguments can only be used as a generic constraint}}
 
   _ = any Sequence<Int>.self
-  // expected-error@-1 {{protocol type with type arguments can only be used as a generic constraint}}
+  // expected-error@-1 {{'self' is not a member type of protocol 'parameterized_protocol.Sequence<Swift.Int>'}}
+
+  _ = (any Sequence<Int>).self
 }
 
 /// Not supported as a protocol composition term for now

diff --git a/validation-test/compiler_crashers_2_fixed/unsupported_recursive_opaque_conformance.swift b/validation-test/compiler_crashers_2_fixed/unsupported_recursive_opaque_conformance.swift
@@ -1,4 +1,4 @@
-// RUN: not %target-swift-frontend -disable-availability-checking -emit-ir -enable-parameterized-existential-types %s
+// RUN: not %target-swift-frontend -disable-availability-checking -emit-ir %s
 
 protocol P<X, Y> {
   associatedtype X : P