TypeCheckType: Unconditionally warn about missing existential any until a future language mode

include/swift/AST/Decl.h

@@ -5580,12 +5580,6 @@ class ProtocolDecl final : public NominalTypeDecl {
   ///   value requirement.
   bool hasSelfOrAssociatedTypeRequirements() const;
 
-  /// Determine whether an existential type constrained by this protocol must
-  /// be written using `any` syntax.
-  ///
-  /// \Note This method takes language feature state into account.
-  bool existentialRequiresAny() const;
-
   /// Returns a list of protocol requirements that must be assessed to
   /// determine a concrete's conformance effect polymorphism kind.
   PolymorphicEffectRequirementList getPolymorphicEffectRequirements(

include/swift/AST/DiagnosticGroups.def

@@ -27,6 +27,7 @@ GROUP(Unsafe, "Unsafe.md")
 GROUP(UnknownWarningGroup, "UnknownWarningGroup.md")
 GROUP(PreconcurrencyImport, "PreconcurrencyImport.md")
 GROUP(StrictLanguageFeatures, "StrictLanguageFeatures.md")
+GROUP(ExistentialAny, "ExistentialAny.md")
 
 #define UNDEFINE_DIAGNOSTIC_GROUPS_MACROS
 #include "swift/AST/DefineDiagnosticGroupsMacros.h"

include/swift/AST/DiagnosticsSema.def

@@ -5839,11 +5839,12 @@ ERROR(any_not_existential,none,
 ERROR(incorrect_optional_any,none,
       "optional 'any' type must be written %0",
       (Type))
-ERROR(existential_requires_any,none,
-      "use of %select{protocol |}2%0 as a type must be written %1",
-      (Type, Type, bool))
-ERROR(inverse_requires_any,none,
-      "constraint that suppresses conformance requires 'any'", ())
+
+GROUPED_ERROR(existential_requires_any,ExistentialAny,none,
+              "use of %select{protocol |}2%0 as a type must be written %1",
+              (Type, Type, bool))
+GROUPED_ERROR(inverse_requires_any,ExistentialAny,none,
+              "constraint that suppresses conformance requires 'any'", ())
 
 ERROR(nonisolated_mutable_storage,none,
       "'nonisolated' cannot be applied to mutable stored properties",

lib/AST/Decl.cpp

@@ -6958,13 +6958,6 @@ bool ProtocolDecl::hasSelfOrAssociatedTypeRequirements() const {
                            resultForCycle);
 }
 
-bool ProtocolDecl::existentialRequiresAny() const {
-  if (getASTContext().LangOpts.hasFeature(Feature::ExistentialAny))
-    return true;
-
-  return hasSelfOrAssociatedTypeRequirements();
-}
-
 ArrayRef<AssociatedTypeDecl *>
 ProtocolDecl::getPrimaryAssociatedTypes() const {
   return evaluateOrDefault(getASTContext().evaluator,

lib/Sema/TypeCheckType.cpp

@@ -907,11 +907,15 @@ static Type applyGenericArguments(Type type,
     auto parameterized =
         ParameterizedProtocolType::get(ctx, protoType, argTys);
 
+    // FIXME: Can this not be done in ExistentialTypeSyntaxChecker?
     if (resolution.getOptions().isConstraintImplicitExistential() &&
         !ctx.LangOpts.hasFeature(Feature::ImplicitSome)) {
-      diags.diagnose(loc, diag::existential_requires_any, parameterized,
-                     ExistentialType::get(parameterized),
-                     /*isAlias=*/isa<TypeAliasType>(type.getPointer()));
+      diags
+          .diagnose(loc, diag::existential_requires_any, parameterized,
+                    ExistentialType::get(parameterized),
+                    /*isAlias=*/isa<TypeAliasType>(type.getPointer()))
+          .warnUntilSwiftVersion(7);
+
       return ErrorType::get(ctx);
     }
 
@@ -6171,18 +6175,15 @@ namespace {
 /// written syntax.
 class ExistentialTypeSyntaxChecker : public ASTWalker {
   ASTContext &Ctx;
-  bool checkStatements;
+  const bool checkStatements;
   bool hitTopStmt;
-  bool warnUntilSwift7;
 
   unsigned exprCount = 0;
   llvm::SmallVector<TypeRepr *, 4> reprStack;
 
 public:
-  ExistentialTypeSyntaxChecker(ASTContext &ctx, bool checkStatements,
-                               bool warnUntilSwift7 = false)
-      : Ctx(ctx), checkStatements(checkStatements), hitTopStmt(false),
-        warnUntilSwift7(warnUntilSwift7) {}
+  ExistentialTypeSyntaxChecker(ASTContext &ctx, bool checkStatements)
+      : Ctx(ctx), checkStatements(checkStatements), hitTopStmt(false) {}
 
   MacroWalking getMacroWalkingBehavior() const override {
     return MacroWalking::ArgumentsAndExpansion;
@@ -6215,7 +6216,7 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
   }
 
   PostWalkAction walkToTypeReprPost(TypeRepr *T) override {
-    assert(reprStack.back() == T);
+    ASSERT(reprStack.back() == T);
     reprStack.pop_back();
     return Action::Continue();
   }
@@ -6339,14 +6340,13 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
     diag.fixItReplace(replacementT->getSourceRange(), fix);
   }
 
-  /// Returns a Boolean value indicating whether the type representation being
-  /// visited, assuming it is a constraint type demanding `any` or `some`, is
-  /// missing either keyword.
-  bool isAnyOrSomeMissing() const {
-    assert(isa<DeclRefTypeRepr>(reprStack.back()));
+  /// Returns a Boolean value indicating whether the currently visited
+  /// `DeclRefTypeRepr` node has a `some` or `any` keyword that applies to it.
+  bool currentNodeHasAnyOrSomeKeyword() const {
+    ASSERT(isa<DeclRefTypeRepr>(reprStack.back()));
 
     if (reprStack.size() < 2) {
-      return true;
+      return false;
     }
 
     auto it = reprStack.end() - 1;
@@ -6356,7 +6356,7 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
         break;
       }
 
-      // Look through parens, inverses, metatypes, and compositions.
+      // Look through parens, inverses, `.Type` metatypes, and compositions.
       if ((*it)->isParenType() || isa<InverseTypeRepr>(*it) ||
           isa<CompositionTypeRepr>(*it) || isa<MetatypeTypeRepr>(*it)) {
         continue;
@@ -6365,84 +6365,119 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
       break;
     }
 
-    return !(isa<OpaqueReturnTypeRepr>(*it) || isa<ExistentialTypeRepr>(*it));
+    return isa<OpaqueReturnTypeRepr>(*it) || isa<ExistentialTypeRepr>(*it);
   }
 
-  void checkDeclRefTypeRepr(DeclRefTypeRepr *T) const {
-    assert(!T->isInvalid());
+  /// Returns the behavior with which to diagnose a missing `any` or `some`
+  /// keyword.
+  ///
+  /// \param constraintTy The constraint type that is missing the keyword.
+  /// \param isInverted Whether the constraint type is an object of an `~`
+  ///  inversion.
+  static bool shouldDiagnoseMissingAnyOrSomeKeyword(Type constraintTy,
+                                                    bool isInverted,
+                                                    ASTContext &ctx) {
+    // `Any` and `AnyObject` are always exempt from `any` syntax.
+    if (constraintTy->isAny() || constraintTy->isAnyObject()) {
+      return false;
+    }
 
-    if (Ctx.LangOpts.hasFeature(Feature::ImplicitSome)) {
-      return;
+    // A missing `any` or `some` is always diagnosed if this feature is enabled.
+    if (ctx.LangOpts.hasFeature(Feature::ExistentialAny)) {
+      return true;
     }
 
-    // Backtrack the stack, looking just through parentheses and metatypes. If
-    // we find an inverse (which always requires `any`), diagnose it specially.
-    if (reprStack.size() > 1) {
-      auto it = reprStack.end() - 2;
-      while (it != reprStack.begin() &&
-             ((*it)->isParenType() || isa<MetatypeTypeRepr>(*it))) {
-        --it;
-        continue;
+    // If the type is inverted, a missing `any` or `some` is always diagnosed.
+    if (isInverted) {
+      return true;
+    }
+
+    // If one of the protocols is inverted, a missing `any` or `some` is
+    // always diagnosed.
+    if (auto *PCT = constraintTy->getAs<ProtocolCompositionType>()) {
+      if (!PCT->getInverses().empty()) {
+        return true;
       }
+    }
 
-      if (auto *inverse = dyn_cast<InverseTypeRepr>(*it);
-          inverse && isAnyOrSomeMissing()) {
-        auto diag = Ctx.Diags.diagnose(inverse->getTildeLoc(),
-                                       diag::inverse_requires_any);
-        diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-        emitInsertAnyFixit(diag, T);
-        return;
+    // If one of the protocols has "Self or associated type" requirements,
+    // a missing `any` or `some` is always diagnosed.
+    auto layout = constraintTy->getExistentialLayout();
+    for (auto *protoDecl : layout.getProtocols()) {
+      if (protoDecl->hasSelfOrAssociatedTypeRequirements()) {
+        return true;
       }
     }
 
+    return false;
+  }
+
+  void checkDeclRefTypeRepr(DeclRefTypeRepr *T) const {
+    if (Ctx.LangOpts.hasFeature(Feature::ImplicitSome)) {
+      return;
+    }
+
     auto *decl = T->getBoundDecl();
     if (!decl) {
       return;
     }
 
-    if (auto *proto = dyn_cast<ProtocolDecl>(decl)) {
-      if (proto->existentialRequiresAny() && isAnyOrSomeMissing()) {
-        auto diag =
-            Ctx.Diags.diagnose(T->getNameLoc(), diag::existential_requires_any,
-                               proto->getDeclaredInterfaceType(),
-                               proto->getDeclaredExistentialType(),
-                               /*isAlias=*/false);
-        diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-        emitInsertAnyFixit(diag, T);
+    if (!isa<ProtocolDecl>(decl) && !isa<TypeAliasDecl>(decl)) {
+      return;
+    }
+
+    // If there is already an `any` or `some` that applies to this node,
+    // move on.
+    if (currentNodeHasAnyOrSomeKeyword()) {
+      return;
+    }
+
+    const auto type = decl->getDeclaredInterfaceType();
+
+    // A type alias may need to be prefixed with `any` only if it stands for a
+    // constraint type.
+    if (isa<TypeAliasDecl>(decl) && !type->isConstraintType()) {
+      return;
+    }
+
+    // First, consider the possibility of the current node being an object of
+    // an inversion, e.g. `~(Copyable)`.
+    // Climb up the stack, looking just through parentheses and `.Type`
+    // metatypes.
+    // If we find an inversion, we will diagnose it specially.
+    InverseTypeRepr *const outerInversion = [&] {
+      if (reprStack.size() < 2) {
+        return (InverseTypeRepr *)nullptr;
       }
-    } else if (auto *alias = dyn_cast<TypeAliasDecl>(decl)) {
-      auto type = Type(alias->getDeclaredInterfaceType()->getDesugaredType());
-
-      // If this is a type alias to a constraint type, the type
-      // alias name must be prefixed with 'any' to be used as an
-      // existential type.
-      if (type->isConstraintType() && !type->isAny() && !type->isAnyObject()) {
-        bool diagnose = false;
-
-        // Look for protocol members that require 'any'.
-        auto layout = type->getExistentialLayout();
-        for (auto *protoDecl : layout.getProtocols()) {
-          if (protoDecl->existentialRequiresAny()) {
-            diagnose = true;
-            break;
-          }
-        }
 
-        // If inverses are present, require 'any' too.
-        if (auto *PCT = type->getAs<ProtocolCompositionType>())
-          diagnose |= !PCT->getInverses().empty();
-
-        if (diagnose && isAnyOrSomeMissing()) {
-          auto diag = Ctx.Diags.diagnose(
-              T->getNameLoc(), diag::existential_requires_any,
-              alias->getDeclaredInterfaceType(),
-              ExistentialType::get(alias->getDeclaredInterfaceType()),
-              /*isAlias=*/true);
-          diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-          emitInsertAnyFixit(diag, T);
-        }
+      auto it = reprStack.end() - 2;
+      while (it != reprStack.begin() &&
+             ((*it)->isParenType() || isa<MetatypeTypeRepr>(*it))) {
+        --it;
+        continue;
       }
+
+      return dyn_cast<InverseTypeRepr>(*it);
+    }();
+
+    if (!shouldDiagnoseMissingAnyOrSomeKeyword(
+            type, /*isInverted=*/outerInversion, this->Ctx)) {
+      return;
+    }
+
+    std::optional<InFlightDiagnostic> diag;
+    if (outerInversion) {
+      diag.emplace(Ctx.Diags.diagnose(outerInversion->getTildeLoc(),
+                                      diag::inverse_requires_any));
+    } else {
+      diag.emplace(Ctx.Diags.diagnose(T->getNameLoc(),
+                                      diag::existential_requires_any, type,
+                                      ExistentialType::get(type),
+                                      /*isAlias=*/isa<TypeAliasDecl>(decl)));
     }
+
+    diag->warnUntilSwiftVersion(7);
+    emitInsertAnyFixit(*diag, T);
   }
 
 public:
@@ -6516,14 +6551,7 @@ void TypeChecker::checkExistentialTypes(ASTContext &ctx, Stmt *stmt,
   if (DC->isInSwiftinterface())
     return;
 
-  // Previously we missed this diagnostic on 'catch' statements, downgrade
-  // to a warning until Swift 7.
-  auto downgradeUntilSwift7 = false;
-  if (auto *CS = dyn_cast<CaseStmt>(stmt))
-    downgradeUntilSwift7 = CS->getParentKind() == CaseParentKind::DoCatch;
-
-  ExistentialTypeSyntaxChecker checker(ctx, /*checkStatements=*/true,
-                                       downgradeUntilSwift7);
+  ExistentialTypeSyntaxChecker checker(ctx, /*checkStatements=*/true);
   stmt->walk(checker);
 }
 

test/Generics/inverse_generics.swift

@@ -475,8 +475,8 @@ func checkExistentials() {
 
 typealias NotCopyable = ~Copyable
 typealias EmptyComposition = ~Copyable & ~Escapable
-func test(_ t: borrowing NotCopyable) {} // expected-error {{use of 'NotCopyable' (aka '~Copyable') as a type must be written 'any NotCopyable'}}
-func test(_ t: borrowing EmptyComposition) {} // expected-error {{use of 'EmptyComposition' (aka '~Copyable & ~Escapable') as a type must be written 'any EmptyComposition' (aka 'any ~Copyable & ~Escapable')}}
+func test(_ t: borrowing NotCopyable) {} // expected-warning {{use of 'NotCopyable' (aka '~Copyable') as a type must be written 'any NotCopyable'}}
+func test(_ t: borrowing EmptyComposition) {} // expected-warning {{use of 'EmptyComposition' (aka '~Copyable & ~Escapable') as a type must be written 'any EmptyComposition' (aka 'any ~Copyable & ~Escapable')}}
 
 typealias Copy = Copyable
 func test(_ z1: Copy, _ z2: Copyable) {}

test/Macros/macros_diagnostics.swift

@@ -196,8 +196,8 @@ struct MyStruct<T: MyProto> {
 
 struct SomeType {
   #genericUnary<Equatable>(0 as Hashable)
-  // expected-error@-1{{use of protocol 'Equatable' as a type must be written 'any Equatable'}}
-  // expected-error@-2{{use of protocol 'Hashable' as a type must be written 'any Hashable'}}
+  // expected-warning@-1{{use of protocol 'Equatable' as a type must be written 'any Equatable'}}
+  // expected-warning@-2{{use of protocol 'Hashable' as a type must be written 'any Hashable'}}
   // expected-error@-3{{external macro implementation type}}
 }
 

test/Macros/top_level_freestanding.swift

@@ -107,12 +107,12 @@ func testGlobalVariable() {
 
 // expected-note @+1 6 {{in expansion of macro 'anonymousTypes' here}}
 #anonymousTypes(causeErrors: true) { "foo" }
-// DIAG_BUFFERS-DAG: @__swiftmacro_9MacroUser0033top_level_freestandingswift_DbGHjfMX108_0_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf0_{{.*}}: error: use of protocol 'Equatable' as a type must be written 'any Equatable'
-// DIAG_BUFFERS-DAG: @__swiftmacro_9MacroUser00142___swiftmacro_9MacroUser0033top_level_freestandingswift_DbGHjfMX108_0_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf0_swift_DAIABdjIbfMX23_2_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll27introduceTypeCheckingErrorsfMf_{{.*}}: error: use of protocol 'Hashable' as a type must be written 'any Hashable'
+// DIAG_BUFFERS-DAG: @__swiftmacro_9MacroUser0033top_level_freestandingswift_DbGHjfMX108_0_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf0_{{.*}}: warning: use of protocol 'Equatable' as a type must be written 'any Equatable'
+// DIAG_BUFFERS-DAG: @__swiftmacro_9MacroUser00142___swiftmacro_9MacroUser0033top_level_freestandingswift_DbGHjfMX108_0_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll14anonymousTypesfMf0_swift_DAIABdjIbfMX23_2_33_082AE7CFEFA6960C804A9FE7366EB5A0Ll27introduceTypeCheckingErrorsfMf_{{.*}}: warning: use of protocol 'Hashable' as a type must be written 'any Hashable'
 
 // expected-note @+1 2 {{in expansion of macro 'anonymousTypes' here}}
 #anonymousTypes { () -> String in
-  // expected-error @+1 {{use of protocol 'Equatable' as a type must be written 'any Equatable'}}
+  // expected-warning @+1 {{use of protocol 'Equatable' as a type must be written 'any Equatable'}}
   _ = 0 as Equatable
   return "foo"
 }

test/decl/nested/protocol.swift

@@ -237,7 +237,7 @@ extension OuterProtocol {
 
 struct ConformsToOuterProtocol : OuterProtocol {
   typealias Hen = Int
-  func f() { let _ = InnerProtocol.self } // expected-error {{use of protocol 'InnerProtocol' as a type must be written 'any InnerProtocol'}}
+  func f() { let _ = InnerProtocol.self } // expected-warning {{use of protocol 'InnerProtocol' as a type must be written 'any InnerProtocol'}}
 }
 
 extension OuterProtocol {