NCGenerics: add availability checking

Not all runtimes can correctly operate with types that use noncopyable
generics. When the generic argument of a type is noncopyable, old
runtimes can't recognize that to correctly check conformances that may
be conditional on those arguments being Copyable, etc.

resolves rdar://126239335

include/swift/AST/DiagnosticsSema.def

@@ -6737,6 +6737,16 @@ ERROR(availability_isolated_any_only_version_newer, none,
       "%0 %1 or newer",
       (StringRef, llvm::VersionTuple))
 
+ERROR(availability_copyable_generics_casting_only_version_newer, none,
+      "runtime support for casting types with noncopyable generic arguments "
+      "is only available in %0 %1 or newer",
+      (StringRef, llvm::VersionTuple))
+
+ERROR(availability_escapable_generics_casting_only_version_newer, none,
+      "runtime support for casting types with nonescapable generic arguments "
+      "is only available in %0 %1 or newer",
+      (StringRef, llvm::VersionTuple))
+
 ERROR(availability_typed_throws_only_version_newer, none,
       "runtime support for typed throws function types is only available in "
       "%0 %1 or newer",

include/swift/AST/FeatureAvailability.def

@@ -71,6 +71,8 @@ FEATURE(SwiftExceptionPersonality,                      (6, 0))
 // Metadata support for @isolated(any) function types
 FEATURE(IsolatedAny,                                    (6, 0))
 
+FEATURE(NoncopyableGenerics,                            (6, 0))
+
 FEATURE(TaskExecutor,                                   FUTURE)
 FEATURE(Differentiation,                                FUTURE)
 FEATURE(InitRawStructMetadata,                          FUTURE)

lib/Sema/TypeCheckAvailability.cpp

@@ -3032,6 +3032,83 @@ static bool diagnoseTypedThrowsAvailability(
       ReferenceDC);
 }
 
+/// Make sure the generic arguments conform to all known invertible protocols.
+/// Runtimes prior to NoncopyableGenerics do not check if any of the
+/// generic arguments conform to Copyable/Escapable during dynamic casts.
+/// But a dynamic cast *needs* to check if the generic arguments conform,
+/// to determine if the cast should be permitted at all. For example:
+///
+///    struct X<T> {}
+///    extension X: P where T: Y {}
+///
+///     func f<Y: ~Copyable>(...) {
+///       let x: X<Y> = ...
+///       _ = x as? any P   // <- cast should fail
+///     }
+///
+/// The dynamic cast here must fail because Y does not conform to Copyable,
+/// thus X<Y> doesn't conform to P!
+///
+/// \param boundTy The generic type with its generic arguments.
+/// \returns the invertible protocol for which a conformance is missing in
+///          one of the generic arguments, or none if all are present for
+///          every generic argument.
+static std::optional<InvertibleProtocolKind> checkGenericArgsForInvertibleReqs(
+    BoundGenericType *boundTy) {
+  for (auto arg : boundTy->getGenericArgs()) {
+    for (auto ip : InvertibleProtocolSet::allKnown()) {
+      switch (ip) {
+      case InvertibleProtocolKind::Copyable:
+        if (arg->isNoncopyable())
+          return ip;
+        break;
+      case InvertibleProtocolKind::Escapable:
+        if (!arg->isEscapable())
+          return ip;
+      }
+    }
+  }
+  return std::nullopt;
+}
+
+/// Older runtimes won't check for required invertible protocol conformances
+/// at runtime during a cast.
+///
+/// \param srcType the source or initial type of the cast
+/// \param refLoc source location of the cast
+/// \param refDC decl context in which the cast occurs
+/// \return true if diagnosed
+static bool checkInverseGenericsCastingAvailability(Type srcType,
+                                                    SourceRange refLoc,
+                                                    const DeclContext *refDC) {
+  if (!srcType) return false;
+
+  auto type = srcType->getCanonicalType();
+
+  if (auto boundTy = dyn_cast<BoundGenericType>(type)) {
+    if (auto missing = checkGenericArgsForInvertibleReqs(boundTy)) {
+      std::optional<Diag<StringRef, llvm::VersionTuple>> diag;
+      switch (*missing) {
+      case InvertibleProtocolKind::Copyable:
+        diag =
+            diag::availability_copyable_generics_casting_only_version_newer;
+        break;
+      case InvertibleProtocolKind::Escapable:
+        diag =
+            diag::availability_escapable_generics_casting_only_version_newer;
+        break;
+      }
+
+      // Enforce the availability restriction.
+      return TypeChecker::checkAvailability(
+          refLoc,
+          refDC->getASTContext().getNoncopyableGenericsAvailability(),
+          *diag,
+          refDC);
+    }
+  }
+}
+
 static bool checkTypeMetadataAvailabilityInternal(CanType type,
                                                   SourceRange refLoc,
                                                   const DeclContext *refDC) {
@@ -3075,7 +3152,13 @@ static bool checkTypeMetadataAvailabilityForConverted(Type refType,
   // there.
   if (type.isAnyExistentialType()) return false;
 
-  return checkTypeMetadataAvailabilityInternal(type, refLoc, refDC);
+  if (checkTypeMetadataAvailabilityInternal(type, refLoc, refDC))
+    return true;
+
+  if (checkInverseGenericsCastingAvailability(type, refLoc, refDC))
+    return true;
+
+  return false;
 }
 
 namespace {
@@ -3476,6 +3559,9 @@ public:
     if (auto EE = dyn_cast<ErasureExpr>(E)) {
       checkTypeMetadataAvailability(EE->getSubExpr()->getType(),
                                     EE->getLoc(), Where.getDeclContext());
+      checkInverseGenericsCastingAvailability(EE->getSubExpr()->getType(),
+                                              EE->getLoc(),
+                                              Where.getDeclContext());
 
       for (ProtocolConformanceRef C : EE->getConformances()) {
         diagnoseConformanceAvailability(E->getLoc(), C, Where, Type(), Type(),

test/Generics/inverse_casting_availability.swift

@@ -0,0 +1,129 @@
+// RUN: %target-typecheck-verify-swift \
+// RUN:   -debug-diagnostic-names -target arm64-apple-macos14.4 \
+// RUN:   -enable-experimental-feature NonescapableTypes
+
+// REQUIRES: OS=macosx || OS=ios || OS=tvos || OS=watchOS || OS=xros
+
+protocol P {}
+struct NCG<T: ~Copyable> {}
+extension NCG: P where T: Copyable {} // expected-note 2{{requirement_implied_by_conditional_conformance}}
+
+struct NEG<T: ~Escapable> {}
+extension NEG: P {} // expected-note {{requirement_implied_by_conditional_conformance}}
+
+struct All {}
+struct NoCopy: ~Copyable {}
+struct NoEscape: ~Escapable {}
+
+
+
+/// MARK: dynamic casts are gated by availability. Older runtimes don't check
+/// for conformance to Copyable so they'll give bogus results.
+
+// expected-note@+1 8{{availability_add_attribute}}
+func dyn_cast_errors<T: ~Copyable, V: ~Escapable>(
+                    _ generic: NCG<T>, _ concrete: NCG<NoCopy>,
+                    _ genericEsc: NEG<V>, _ concreteEsc: NEG<NoEscape>) {
+  _ = concrete as? any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = generic as? any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  _ = concrete is any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = generic is any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  _ = concrete as! any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = generic as! any P // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  _ = genericEsc as? any P // expected-error {{availability_escapable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = concreteEsc is any P // expected-error {{availability_escapable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+}
+
+@available(SwiftStdlib 6.0, *)
+func FIXED_dyn_cast_errors<T: ~Copyable, V: ~Escapable>(
+                          _ generic: NCG<T>, _ concrete: NCG<NoCopy>,
+                          _ genericEsc: NEG<V>, _ concreteEsc: NEG<NoEscape>) {
+  _ = concrete as? any P
+  _ = generic as? any P
+
+  _ = concrete is any P
+  _ = generic is any P
+
+  _ = concrete as! any P
+  _ = generic as! any P
+
+  _ = genericEsc as? any P
+  _ = concreteEsc is any P
+}
+
+func noAvailabilityNeeded<T>(_ generic: NCG<T>, _ concrete: NCG<All>) {
+  _ = concrete as? any P // expected-warning {{conditional_downcast_coercion}}
+  _ = generic as? any P  // expected-warning {{conditional_downcast_coercion}}
+
+  _ = concrete is any P  // expected-warning {{isa_is_always_true}}
+  _ = generic is any P   // expected-warning {{isa_is_always_true}}
+
+  _ = concrete as! any P // expected-warning {{forced_downcast_coercion}}
+  _ = generic as! any P  // expected-warning {{forced_downcast_coercion}}
+
+  _ = concrete as any P
+  _ = generic as any P
+
+  _ = concrete as Any
+  _ = generic as Any
+}
+
+func expected_checked_cast_errors<T: ~Copyable>(_ generic: NCG<T>, _ concrete: NCG<NoCopy>,
+                                                _ concreteEsc: NEG<NoEscape>) {
+  _ = concrete as any P // expected-error {{type_does_not_conform_decl_owner}}
+  _ = generic as any P  // expected-error {{type_does_not_conform_decl_owner}}
+  _ = concreteEsc as any P // expected-error {{type_does_not_conform_decl_owner}}
+}
+
+/// MARK: existential erasure requires availability, because later dynamic casts
+/// of that erased type will not correctly check for Copyable generic args.
+
+func eraseImplicit(_ a: Any) {}
+
+// expected-note@+1 9{{availability_add_attribute}}
+func erasure_cast_disallowed<T: ~Copyable>(_ generic: NCG<T>, _ concrete: NCG<NoCopy>, _ concreteEsc: NEG<NoEscape>) -> Any {
+  _ = concrete as Any // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = concreteEsc as Any // expected-error {{availability_escapable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  _ = generic as Any // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  let _: Any = concrete // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  let _: Any = generic // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  let _: Any = { concreteEsc }() // expected-error {{availability_escapable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  eraseImplicit(concrete) // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+  eraseImplicit(generic) // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+
+  return concrete // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+}
+
+struct Box<Wrapped: ~Copyable>: ~Copyable { // expected-note {{availability_add_attribute}}
+  private let _pointer: UnsafeMutablePointer<Wrapped>
+
+  init(_ element: consuming Wrapped) { // expected-note {{availability_add_attribute}}
+    _pointer = .allocate(capacity: 1)
+    print("allocating",_pointer) // expected-error {{availability_copyable_generics_casting_only_version_newer}} // expected-note {{availability_guard_with_version_check}}
+    _pointer.initialize(to: element)
+  }
+}
+
+/// MARK: misc. operations that are permitted
+
+public protocol Debatable: ~Copyable {}
+
+public func asExistential(_ t: consuming any Debatable & ~Copyable) {}
+
+public func hello<T: Debatable & ~Copyable>(_ t: consuming T) {
+  asExistential(t)
+}
+
+extension UnsafeMutableRawPointer {
+  public func blahInitializeMemory<T: ~Copyable>(
+      as type: T.Type, from source: UnsafeMutablePointer<T>, count: Int
+    ) {
+      _ = UnsafeMutableRawPointer(source + count)
+  }
+}

test/Interpreter/moveonly_generics_casting.swift

@@ -1,5 +1,5 @@
-// RUN: %target-run-simple-swift(-Xfrontend -sil-verify-all) | %FileCheck %s
-// RUN: %target-run-simple-swift(-O -Xfrontend -sil-verify-all) | %FileCheck %s
+// RUN: %target-run-simple-swift(-Xfrontend -sil-verify-all -Xfrontend -disable-availability-checking) | %FileCheck %s
+// RUN: %target-run-simple-swift(-O -Xfrontend -sil-verify-all -Xfrontend -disable-availability-checking) | %FileCheck %s
 
 // REQUIRES: executable_test
 

test/SILOptimizer/moveonly_borrowing_switch_yield.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -parse-as-library -O -emit-sil -verify %s
+// RUN: %target-swift-frontend -parse-as-library -O -emit-sil -verify %s -disable-availability-checking
 
 extension List {
     var peek: Element {
@@ -13,30 +13,8 @@ extension List {
     }
 }
 
-struct MyPointer<Wrapped: ~Copyable>: Copyable {
-    var v: UnsafeMutablePointer<Int>
-
-    static func allocate(capacity: Int) -> Self {
-        fatalError()
-    }
-
-    func initialize(to: consuming Wrapped) {
-    }
-    func deinitialize(count: Int) {
-    }
-    func deallocate() {
-    }
-    func move() -> Wrapped {
-        fatalError()
-    }
-
-    var pointee: Wrapped {
-        _read { fatalError() }
-    }
-}
-
 struct Box<Wrapped: ~Copyable>: ~Copyable {
-    private let _pointer: MyPointer<Wrapped>
+    private let _pointer: UnsafeMutablePointer<Wrapped>
     
     init(_ element: consuming Wrapped) {
         _pointer = .allocate(capacity: 1)

test/SILOptimizer/moveonly_consuming_switch.swift

@@ -1,27 +1,7 @@
-// RUN: %target-swift-frontend -emit-sil -verify %s
-
-// TODO: Remove this and just use the real `UnsafeMutablePointer` when
-// noncopyable type support has been upstreamed.
-struct MyPointer<Wrapped: ~Copyable>: Copyable {
-    var v: UnsafeMutablePointer<Int>
-
-    static func allocate(capacity: Int) -> Self {
-        fatalError()
-    }
-
-    func initialize(to: consuming Wrapped) {
-    }
-    func deinitialize(count: Int) {
-    }
-    func deallocate() {
-    }
-    func move() -> Wrapped {
-        fatalError()
-    }
-}
+// RUN: %target-swift-frontend -emit-sil -verify %s -disable-availability-checking
 
 struct Box<Wrapped: ~Copyable>: ~Copyable {
-    private let _pointer: MyPointer<Wrapped>
+    private let _pointer: UnsafeMutablePointer<Wrapped>
     
     init(_ element: consuming Wrapped) {
         _pointer = .allocate(capacity: 1)