[AST] Allocate PlaceholderTypes in the correct arena

include/swift/AST/Types.h

@@ -173,7 +173,13 @@ class RecursiveTypeProperties {
     /// This type contains an ElementArchetype.
     HasElementArchetype = 0x4000,
 
-    Last_Property = HasElementArchetype
+    /// Whether the type is allocated in the constraint solver arena. This can
+    /// differ from \c HasTypeVariable for types such as placeholders, which do
+    /// not have type variables, but we still want to allocate in the solver if
+    /// they have a type variable originator.
+    SolverAllocated = 0x8000,
+
+    Last_Property = SolverAllocated
   };
   enum { BitWidth = countBitsUsed(Property::Last_Property) };
 
@@ -224,6 +230,12 @@ class RecursiveTypeProperties {
   /// opened element archetype?
   bool hasElementArchetype() const { return Bits & HasElementArchetype; }
 
+  /// Whether the type is allocated in the constraint solver arena. This can
+  /// differ from \c hasTypeVariable() for types such as placeholders, which
+  /// do not have type variables, but we still want to allocate in the solver if
+  /// they have a type variable originator.
+  bool isSolverAllocated() const { return Bits & SolverAllocated; }
+
   /// Does a type with these properties structurally contain a local
   /// archetype?
   bool hasLocalArchetype() const {
@@ -501,6 +513,8 @@ class alignas(1 << TypeAlignInBits) TypeBase
   }
 
   void setRecursiveProperties(RecursiveTypeProperties properties) {
+    assert(!(properties.hasTypeVariable() && !properties.isSolverAllocated()) &&
+           "type variables must be solver allocated!");
     Bits.TypeBase.Properties = properties.getBits();
     assert(Bits.TypeBase.Properties == properties.getBits() && "Bits dropped!");
   }
@@ -6714,8 +6728,9 @@ TypeVariableType : public TypeBase {
   // type is opaque.
 
   TypeVariableType(const ASTContext &C, unsigned ID)
-    : TypeBase(TypeKind::TypeVariable, &C,
-               RecursiveTypeProperties::HasTypeVariable) {
+      : TypeBase(TypeKind::TypeVariable, &C,
+                 RecursiveTypeProperties::HasTypeVariable |
+                     RecursiveTypeProperties::SolverAllocated) {
     // Note: the ID may overflow (current limit is 2^20 - 1).
     Bits.TypeVariableType.ID = ID;
     if (Bits.TypeVariableType.ID != ID) {
@@ -6774,6 +6789,8 @@ DEFINE_EMPTY_CAN_TYPE_WRAPPER(TypeVariableType, Type)
 /// because the expression is ambiguous. This type is only used by the
 /// constraint solver and transformed into UnresolvedType to be used in AST.
 class PlaceholderType : public TypeBase {
+  // NOTE: If you add a new Type-based originator, you'll need to update the
+  // recursive property logic in PlaceholderType::get.
   using Originator =
       llvm::PointerUnion<TypeVariableType *, DependentMemberType *, VarDecl *,
                          ErrorExpr *, PlaceholderTypeRepr *>;

lib/AST/ASTContext.cpp

@@ -430,6 +430,7 @@ struct ASTContext::Implementation {
     llvm::DenseMap<Type, InOutType*> InOutTypes;
     llvm::DenseMap<std::pair<Type, void*>, DependentMemberType *>
       DependentMemberTypes;
+    llvm::DenseMap<void *, PlaceholderType *> PlaceholderTypes;
     llvm::DenseMap<Type, DynamicSelfType *> DynamicSelfTypes;
     llvm::DenseMap<std::pair<EnumDecl*, Type>, EnumType*> EnumTypes;
     llvm::DenseMap<std::pair<StructDecl*, Type>, StructType*> StructTypes;
@@ -1811,9 +1812,8 @@ bool ASTContext::hadError() const {
 
 /// Retrieve the arena from which we should allocate storage for a type.
 static AllocationArena getArena(RecursiveTypeProperties properties) {
-  bool hasTypeVariable = properties.hasTypeVariable();
-  return hasTypeVariable ? AllocationArena::ConstraintSolver
-                         : AllocationArena::Permanent;
+  return properties.isSolverAllocated() ? AllocationArena::ConstraintSolver
+                                        : AllocationArena::Permanent;
 }
 
 void ASTContext::addSearchPath(StringRef searchPath, bool isFramework,
@@ -3117,15 +3117,43 @@ Type ErrorType::get(Type originalType) {
   void *mem = ctx.Allocate(sizeof(ErrorType) + sizeof(Type),
                            alignof(ErrorType), arena);
   RecursiveTypeProperties properties = RecursiveTypeProperties::HasError;
-  if (originalProperties.hasTypeVariable())
-    properties |= RecursiveTypeProperties::HasTypeVariable;
+
+  // We need to preserve the solver allocated bit, to ensure any wrapping
+  // types are solver allocated too.
+  if (originalProperties.isSolverAllocated())
+    properties |= RecursiveTypeProperties::SolverAllocated;
+
   return entry = new (mem) ErrorType(ctx, originalType, properties);
 }
 
 Type PlaceholderType::get(ASTContext &ctx, Originator originator) {
   assert(originator);
-  return new (ctx, AllocationArena::Permanent)
-      PlaceholderType(ctx, originator, RecursiveTypeProperties::HasPlaceholder);
+
+  auto originatorProps = [&]() -> RecursiveTypeProperties {
+    if (auto *tv = originator.dyn_cast<TypeVariableType *>())
+      return tv->getRecursiveProperties();
+
+    if (auto *depTy = originator.dyn_cast<DependentMemberType *>())
+      return depTy->getRecursiveProperties();
+
+    return RecursiveTypeProperties();
+  }();
+  auto arena = getArena(originatorProps);
+
+  auto &cache = ctx.getImpl().getArena(arena).PlaceholderTypes;
+  auto &entry = cache[originator.getOpaqueValue()];
+  if (entry)
+    return entry;
+
+  RecursiveTypeProperties properties = RecursiveTypeProperties::HasPlaceholder;
+
+  // We need to preserve the solver allocated bit, to ensure any wrapping
+  // types are solver allocated too.
+  if (originatorProps.isSolverAllocated())
+    properties |= RecursiveTypeProperties::SolverAllocated;
+
+  entry = new (ctx, arena) PlaceholderType(ctx, originator, properties);
+  return entry;
 }
 
 BuiltinIntegerType *BuiltinIntegerType::get(BuiltinIntegerWidth BitWidth,
@@ -3943,7 +3971,7 @@ isAnyFunctionTypeCanonical(ArrayRef<AnyFunctionType::Param> params,
 static RecursiveTypeProperties
 getGenericFunctionRecursiveProperties(ArrayRef<AnyFunctionType::Param> params,
                                       Type result) {
-  static_assert(RecursiveTypeProperties::BitWidth == 15,
+  static_assert(RecursiveTypeProperties::BitWidth == 16,
                 "revisit this if you add new recursive type properties");
   RecursiveTypeProperties properties;
 
@@ -4604,7 +4632,7 @@ CanSILFunctionType SILFunctionType::get(
   void *mem = ctx.Allocate(bytes, alignof(SILFunctionType));
 
   RecursiveTypeProperties properties;
-  static_assert(RecursiveTypeProperties::BitWidth == 15,
+  static_assert(RecursiveTypeProperties::BitWidth == 16,
                 "revisit this if you add new recursive type properties");
   for (auto &param : params)
     properties |= param.getInterfaceType()->getRecursiveProperties();

lib/Sema/CSApply.cpp

@@ -8475,8 +8475,8 @@ namespace {
       exprType = solution.simplifyType(exprType);
       // assert((!expr->getType() || expr->getType()->isEqual(exprType)) &&
       //       "Mismatched types!");
-      assert(!exprType->hasTypeVariable() &&
-             "Should not write type variable into expression!");
+      assert(!exprType->getRecursiveProperties().isSolverAllocated() &&
+             "Should not write solver allocated type into expression!");
       assert(!exprType->hasPlaceholder() &&
              "Should not write type placeholders into expression!");
       expr->setType(exprType);
@@ -8486,8 +8486,10 @@ namespace {
           Type componentType;
           if (cs.hasType(kp, i)) {
             componentType = solution.simplifyType(cs.getType(kp, i));
-            assert(!componentType->hasTypeVariable() &&
-                   "Should not write type variable into key-path component");
+            assert(
+                !componentType->getRecursiveProperties().isSolverAllocated() &&
+                "Should not write solver allocated type into key-path "
+                "component!");
             assert(!componentType->hasPlaceholder() &&
                    "Should not write type placeholder into key-path component");
             kp->getMutableComponents()[i].setComponentType(componentType);

test/Constraints/rdar44770297.swift

@@ -8,4 +8,8 @@ func foo<T: P>(_: () throws -> T) -> T.A? { // expected-note {{where 'T' = 'Neve
   fatalError()
 }
 
-let _ = foo() {fatalError()} & nil // expected-error {{global function 'foo' requires that 'Never' conform to 'P'}}
+let _ = foo() {fatalError()} & nil
+// expected-error@-1 {{global function 'foo' requires that 'Never' conform to 'P'}}
+// expected-error@-2 {{value of optional type 'Never.A?' must be unwrapped to a value of type 'Never.A'}}
+// expected-note@-3 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
+// expected-note@-4 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}

validation-test/Sema/type_checker_crashers_fixed/issue-65360.swift

@@ -13,7 +13,8 @@ let _: () -> Void = {
   // expected-error@-1 {{cannot convert value of type 'Any?' to specified type '(_, _)}}
 }
 
-let _: () -> Void = { // expected-error {{unable to infer closure type in the current context}}
+let _: () -> Void = {
   for case (0)? in [a] {}
   for case (0, 0) in [a] {}
+  // expected-error@-1 {{cannot convert value of type 'Any?' to expected element type '(_, _)'}}
 }