Diagnose Availability for Parameterized Existential Types

include/swift/AST/ASTContext.h

@@ -868,6 +868,10 @@ class ASTContext final {
   /// swift_isUniquelyReferenced functions.
   AvailabilityContext getObjCIsUniquelyReferencedAvailability();
 
+  /// Get the runtime availability of metadata manipulation runtime functions
+  /// for extended existential types.
+  AvailabilityContext getParameterizedExistentialRuntimeAvailability();
+
   /// Get the runtime availability of features introduced in the Swift 5.2
   /// compiler for the target platform.
   AvailabilityContext getSwift52Availability();

include/swift/AST/DiagnosticsSema.def

@@ -5589,6 +5589,11 @@ ERROR(availability_concurrency_only_version_newer, none,
       "concurrency is only available in %0 %1 or newer",
       (StringRef, llvm::VersionTuple))
 
+ERROR(availability_parameterized_protocol_only_version_newer, none,
+      "runtime support for parameterized protocol types is only available in "
+      "%0 %1 or newer",
+      (StringRef, llvm::VersionTuple))
+
 NOTE(availability_guard_with_version_check, none,
      "add 'if #available' version check", ())
 

include/swift/AST/Types.h

@@ -163,7 +163,10 @@ class RecursiveTypeProperties {
     /// type sequence
     HasTypeSequence = 0x1000,
 
-    Last_Property = HasTypeSequence
+    /// This type contains a parameterized existential type \c any P<T>.
+    HasParameterizedExistential = 0x2000,
+
+    Last_Property = HasParameterizedExistential
   };
   enum { BitWidth = countBitsUsed(Property::Last_Property) };
 
@@ -223,6 +226,12 @@ class RecursiveTypeProperties {
 
   bool hasTypeSequence() const { return Bits & HasTypeSequence; }
 
+  /// Does a type with these properties structurally contain a
+  /// parameterized existential type?
+  bool hasParameterizedExistential() const {
+    return Bits & HasParameterizedExistential;
+  }
+
   /// Returns the set of properties present in either set.
   friend RecursiveTypeProperties operator|(Property lhs, Property rhs) {
     return RecursiveTypeProperties(unsigned(lhs) | unsigned(rhs));
@@ -626,6 +635,11 @@ class alignas(1 << TypeAlignInBits) TypeBase
     return getRecursiveProperties().hasTypeSequence();
   }
 
+  /// Determine whether the type involves a parameterized existential type.
+  bool hasParameterizedExistential() const {
+    return getRecursiveProperties().hasParameterizedExistential();
+  }
+
   /// Determine whether the type involves the given opened existential
   /// archetype.
   bool hasOpenedExistentialWithRoot(const OpenedArchetypeType *root) const;

lib/AST/ASTContext.cpp

@@ -3441,6 +3441,8 @@ ExistentialMetatypeType::get(Type T, Optional<MetatypeRepresentation> repr,
     T = existential->getConstraintType();
 
   auto properties = T->getRecursiveProperties();
+  if (T->is<ParameterizedProtocolType>())
+    properties |= RecursiveTypeProperties::HasParameterizedExistential;
   auto arena = getArena(properties);
 
   unsigned reprKey;
@@ -3536,7 +3538,7 @@ isAnyFunctionTypeCanonical(ArrayRef<AnyFunctionType::Param> params,
 static RecursiveTypeProperties
 getGenericFunctionRecursiveProperties(ArrayRef<AnyFunctionType::Param> params,
                                       Type result) {
-  static_assert(RecursiveTypeProperties::BitWidth == 13,
+  static_assert(RecursiveTypeProperties::BitWidth == 14,
                 "revisit this if you add new recursive type properties");
   RecursiveTypeProperties properties;
 
@@ -4139,7 +4141,7 @@ CanSILFunctionType SILFunctionType::get(
   void *mem = ctx.Allocate(bytes, alignof(SILFunctionType));
 
   RecursiveTypeProperties properties;
-  static_assert(RecursiveTypeProperties::BitWidth == 13,
+  static_assert(RecursiveTypeProperties::BitWidth == 14,
                 "revisit this if you add new recursive type properties");
   for (auto &param : params)
     properties |= param.getInterfaceType()->getRecursiveProperties();
@@ -4257,6 +4259,8 @@ Type ExistentialType::get(Type constraint, bool forceExistential) {
   assert(constraint->isConstraintType());
 
   auto properties = constraint->getRecursiveProperties();
+  if (constraint->is<ParameterizedProtocolType>())
+    properties |= RecursiveTypeProperties::HasParameterizedExistential;
   auto arena = getArena(properties);
 
   auto &entry = C.getImpl().getArena(arena).ExistentialTypes[constraint];

lib/AST/Availability.cpp

@@ -394,6 +394,11 @@ AvailabilityContext ASTContext::getObjCIsUniquelyReferencedAvailability() {
   return getSwift56Availability();
 }
 
+AvailabilityContext
+ASTContext::getParameterizedExistentialRuntimeAvailability() {
+  return getSwift57Availability();
+}
+
 AvailabilityContext ASTContext::getSwift52Availability() {
   auto target = LangOpts.Target;
 

lib/Sema/TypeCheckAvailability.cpp

@@ -15,11 +15,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "TypeCheckAvailability.h"
+#include "MiscDiagnostics.h"
 #include "TypeCheckConcurrency.h"
-#include "TypeChecker.h"
 #include "TypeCheckObjC.h"
-#include "MiscDiagnostics.h"
+#include "TypeChecker.h"
 #include "swift/AST/ASTWalker.h"
+#include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/Initializer.h"
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/Pattern.h"
@@ -2773,6 +2774,74 @@ bool isSubscriptReturningString(const ValueDecl *D, ASTContext &Context) {
   return resultTy->isString();
 }
 
+static bool diagnosePotentialParameterizedProtocolUnavailability(
+    SourceRange ReferenceRange, const DeclContext *ReferenceDC,
+    const UnavailabilityReason &Reason) {
+  ASTContext &Context = ReferenceDC->getASTContext();
+
+  auto RequiredRange = Reason.getRequiredOSVersionRange();
+  {
+    auto Err = Context.Diags.diagnose(
+        ReferenceRange.Start,
+        diag::availability_parameterized_protocol_only_version_newer,
+        prettyPlatformString(targetPlatform(Context.LangOpts)),
+        Reason.getRequiredOSVersionRange().getLowerEndpoint());
+
+    // Direct a fixit to the error if an existing guard is nearly-correct
+    if (fixAvailabilityByNarrowingNearbyVersionCheck(
+            ReferenceRange, ReferenceDC, RequiredRange, Context, Err))
+      return true;
+  }
+  fixAvailability(ReferenceRange, ReferenceDC, RequiredRange, Context);
+  return true;
+}
+
+bool swift::diagnoseParameterizedProtocolAvailability(
+    SourceRange ReferenceRange, const DeclContext *ReferenceDC) {
+  // Check the availability of parameterized existential runtime support.
+  ASTContext &ctx = ReferenceDC->getASTContext();
+  if (ctx.LangOpts.DisableAvailabilityChecking)
+    return false;
+
+  if (!shouldCheckAvailability(ReferenceDC->getAsDecl()))
+    return false;
+
+  auto runningOS = TypeChecker::overApproximateAvailabilityAtLocation(
+      ReferenceRange.Start, ReferenceDC);
+  auto availability = ctx.getParameterizedExistentialRuntimeAvailability();
+  if (!runningOS.isContainedIn(availability)) {
+    return diagnosePotentialParameterizedProtocolUnavailability(
+        ReferenceRange, ReferenceDC,
+        UnavailabilityReason::requiresVersionRange(
+            availability.getOSVersion()));
+  }
+  return false;
+}
+
+static void
+maybeDiagParameterizedExistentialErasure(ErasureExpr *EE,
+                                         const ExportContext &Where) {
+  if (auto *OE = dyn_cast<OpaqueValueExpr>(EE->getSubExpr())) {
+    auto *OAT = OE->getType()->getAs<OpenedArchetypeType>();
+    if (!OAT)
+      return;
+
+    auto opened = OAT->getGenericEnvironment()->getOpenedExistentialType();
+    if (!opened || !opened->hasParameterizedExistential())
+      return;
+
+    (void)diagnoseParameterizedProtocolAvailability(EE->getLoc(),
+                                                    Where.getDeclContext());
+  }
+
+  if (EE->getType() &&
+      EE->getType()->isAny() &&
+      EE->getSubExpr()->getType()->hasParameterizedExistential()) {
+    (void)diagnoseParameterizedProtocolAvailability(EE->getLoc(),
+                                                    Where.getDeclContext());
+  }
+}
+
 bool swift::diagnoseExplicitUnavailability(
     const ValueDecl *D,
     SourceRange R,
@@ -2989,6 +3058,17 @@ class ExprAvailabilityWalker : public ASTWalker {
       diagnoseDeclRefAvailability(Context.getRegexDecl(), Range);
       diagnoseDeclRefAvailability(RLE->getInitializer(), Range);
     }
+    if (auto *EE = dyn_cast<ErasureExpr>(E)) {
+      maybeDiagParameterizedExistentialErasure(EE, Where);
+    }
+    if (auto *CC = dyn_cast<ExplicitCastExpr>(E)) {
+      if (!isa<CoerceExpr>(CC) &&
+          CC->getCastType()->hasParameterizedExistential()) {
+        SourceLoc loc = CC->getCastTypeRepr() ? CC->getCastTypeRepr()->getLoc()
+                                              : E->getLoc();
+        diagnoseParameterizedProtocolAvailability(loc, Where.getDeclContext());
+      }
+    }
     if (auto KP = dyn_cast<KeyPathExpr>(E)) {
       maybeDiagKeyPath(KP);
     }
@@ -3749,7 +3829,12 @@ class ProblematicTypeFinder : public TypeDeclFinder {
 
     ModuleDecl *useModule = Where.getDeclContext()->getParentModule();
     auto subs = ty->getContextSubstitutionMap(useModule, ty->getDecl());
-    (void) diagnoseSubstitutionMapAvailability(Loc, subs, Where);
+    (void)diagnoseSubstitutionMapAvailability(
+        Loc, subs, Where,
+        /*depTy=*/Type(),
+        /*replacementTy=*/Type(),
+        /*useConformanceAvailabilityErrorsOption=*/false,
+        /*suppressParameterizationCheckForOptional=*/ty->isOptional());
     return Action::Continue;
   }
 
@@ -3781,6 +3866,19 @@ class ProblematicTypeFinder : public TypeDeclFinder {
       }
     }
 
+    if (auto *TT = T->getAs<TupleType>()) {
+      for (auto component : TT->getElementTypes()) {
+        // Let the walker find inner tuple types, we only want to diagnose
+        // non-compound components.
+        if (component->is<TupleType>())
+          continue;
+
+        if (component->hasParameterizedExistential())
+          (void)diagnoseParameterizedProtocolAvailability(
+              Loc, Where.getDeclContext());
+      }
+    }
+
     return TypeDeclFinder::walkToTypePost(T);
   }
 };
@@ -3895,14 +3993,27 @@ swift::diagnoseSubstitutionMapAvailability(SourceLoc loc,
                                            SubstitutionMap subs,
                                            const ExportContext &where,
                                            Type depTy, Type replacementTy,
-                                           bool useConformanceAvailabilityErrorsOption) {
+                                           bool useConformanceAvailabilityErrorsOption,
+                                           bool suppressParameterizationCheckForOptional) {
   bool hadAnyIssues = false;
   for (ProtocolConformanceRef conformance : subs.getConformances()) {
     if (diagnoseConformanceAvailability(loc, conformance, where,
                                         depTy, replacementTy,
                                         useConformanceAvailabilityErrorsOption))
       hadAnyIssues = true;
   }
+
+  // If we're looking at \c (any P)? (or any other depth of optional) then
+  // there's no availability problem.
+  if (suppressParameterizationCheckForOptional)
+    return hadAnyIssues;
+
+  for (auto replacement : subs.getReplacementTypes()) {
+    if (replacement->hasParameterizedExistential())
+      if (diagnoseParameterizedProtocolAvailability(loc,
+                                                    where.getDeclContext()))
+        hadAnyIssues = true;
+  }
   return hadAnyIssues;
 }
 

lib/Sema/TypeCheckAvailability.h

@@ -224,13 +224,14 @@ diagnoseConformanceAvailability(SourceLoc loc,
                                 Type replacementTy=Type(),
                                 bool useConformanceAvailabilityErrorsOption = false);
 
-bool
-diagnoseSubstitutionMapAvailability(SourceLoc loc,
-                                    SubstitutionMap subs,
-                                    const ExportContext &context,
-                                    Type depTy=Type(),
-                                    Type replacementTy=Type(),
-                                    bool useConformanceAvailabilityErrorsOption = false);
+bool diagnoseSubstitutionMapAvailability(
+    SourceLoc loc,
+    SubstitutionMap subs, 
+    const ExportContext &context,
+    Type depTy = Type(),
+    Type replacementTy = Type(),
+    bool useConformanceAvailabilityErrorsOption = false,
+    bool suppressParameterizationCheckForOptional = false);
 
 /// Diagnose uses of unavailable declarations. Returns true if a diagnostic
 /// was emitted.
@@ -267,6 +268,11 @@ bool diagnoseExplicitUnavailability(
     const ExportContext &where,
     bool useConformanceAvailabilityErrorsOption = false);
 
+/// Diagnose uses of the runtime features of parameterized protools. Returns
+/// \c true if a diagnostic was emitted.
+bool diagnoseParameterizedProtocolAvailability(SourceRange loc,
+                                               const DeclContext *DC);
+
 /// Check if \p decl has a introduction version required by -require-explicit-availability
 void checkExplicitAvailability(Decl *decl);
 

lib/Sema/TypeCheckProtocol.cpp

@@ -4919,6 +4919,17 @@ void ConformanceChecker::ensureRequirementsAreSatisfied() {
   if (where.isImplicit())
     return;
 
+  Conformance->forEachTypeWitness([&](const AssociatedTypeDecl *assoc,
+                                      Type type, TypeDecl *typeDecl) -> bool {
+    // Make sure any associated type witnesses don't make reference to a
+    // parameterized existential type, or we're going to have trouble at
+    // runtime.
+    if (type->hasParameterizedExistential())
+      (void)diagnoseParameterizedProtocolAvailability(typeDecl->getLoc(),
+                                                      where.getDeclContext());
+    return false;
+  });
+
   for (auto req : proto->getRequirementSignature().getRequirements()) {
     if (req.getKind() == RequirementKind::Conformance) {
       auto depTy = req.getFirstType();

test/Constraints/parameterized_existential_metatypes.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-parameterized-existential-types
+// RUN: %target-typecheck-verify-swift -enable-parameterized-existential-types -disable-availability-checking
 //
 // FIXME: Merge this file with existential_metatypes.swift once -enable-parameterized-existential-types becomes the default
 

test/Interpreter/parameterized_existentials.swift

@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-Xfrontend -enable-parameterized-existential-types)
+// RUN: %target-run-simple-swift(-Xfrontend -enable-parameterized-existential-types -Xfrontend -disable-availability-checking)
 // REQUIRES: executable_test
 
 // This test requires the new existential shape metadata accessors which are 

test/RemoteAST/parameterized_existentials.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-remoteast-test -enable-parameterized-existential-types %s | %FileCheck %s
+// RUN: %target-swift-remoteast-test -enable-parameterized-existential-types -disable-availability-checking %s | %FileCheck %s
 
 // REQUIRES: swift-remoteast-test
 

test/SILGen/parameterized_existentials.swift

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

test/SILOptimizer/cast_folding_parameterized_protocol.swift

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