AST: Clean up ExistentialLayout for ParameterizedProtocolType

Author: slavapestov

include/swift/AST/ExistentialLayout.h

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines the ExistentialLayout struct.
+// The ExistentialLayout struct describes the in-memory layout of an existential
+// type.
+//
+// It flattens and canonicalizes protocol compositions, and also expands defaults
+// for invertible protocols.
 //
 //===----------------------------------------------------------------------===//
 
@@ -33,7 +37,6 @@ struct ExistentialLayout {
     hasExplicitAnyObject = false;
     containsObjCProtocol = false;
     containsSwiftProtocol = false;
-    containsParameterized = false;
     representsAnyObject = false;
   }
 
@@ -53,9 +56,6 @@ struct ExistentialLayout {
   /// Whether any protocol members require a witness table.
   bool containsSwiftProtocol : 1;
 
-  /// Whether any protocol members are parameterized.s
-  bool containsParameterized : 1;
-
   /// Whether this layout is the canonical layout for plain-old 'AnyObject'.
   bool representsAnyObject : 1;
 
@@ -105,14 +105,18 @@ struct ExistentialLayout {
   /// calling this on a temporary is likely to be incorrect.
   ArrayRef<ProtocolDecl*> getProtocols() const && = delete;
 
+  ArrayRef<ParameterizedProtocolType *> getParameterizedProtocols() const & {
+    return parameterized;
+  }
+  /// The returned ArrayRef points to internal storage, so
+  /// calling this on a temporary is likely to be incorrect.
+  ArrayRef<ProtocolDecl*> getParameterizedProtocols() const && = delete;
+
   LayoutConstraint getLayoutConstraint() const;
 
 private:
   SmallVector<ProtocolDecl *, 4> protocols;
-
-  /// Zero or more primary associated type requirements from a
-  /// ParameterizedProtocolType
-  ArrayRef<Type> sameTypeRequirements;
+  SmallVector<ParameterizedProtocolType *, 4> parameterized;
 };
 
 }

lib/AST/Type.cpp

@@ -305,7 +305,6 @@ ExistentialLayout::ExistentialLayout(CanProtocolType type) {
   containsObjCProtocol = protoDecl->isObjC();
   containsSwiftProtocol = (!protoDecl->isObjC() &&
                            !protoDecl->isMarkerProtocol());
-  containsParameterized = false;
   representsAnyObject = false;
 
   protocols.push_back(protoDecl);
@@ -316,7 +315,6 @@ ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
   hasExplicitAnyObject = type->hasExplicitAnyObject();
   containsObjCProtocol = false;
   containsSwiftProtocol = false;
-  containsParameterized = false;
 
   auto members = type.getMembers();
   if (!members.empty() &&
@@ -331,9 +329,9 @@ ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
     if (auto protocolType = dyn_cast<ProtocolType>(member)) {
       protoDecl = protocolType->getDecl();
     } else {
-      auto parameterized = cast<ParameterizedProtocolType>(member);
-      protoDecl = parameterized->getProtocol();
-      containsParameterized = true;
+      auto *parameterizedType = member->castTo<ParameterizedProtocolType>();
+      protoDecl = parameterizedType->getProtocol();
+      parameterized.push_back(parameterizedType);
     }
     if (protoDecl->isObjC())
       containsObjCProtocol = true;
@@ -366,8 +364,7 @@ ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
 
 ExistentialLayout::ExistentialLayout(CanParameterizedProtocolType type)
     : ExistentialLayout(type.getBaseType()) {
-  sameTypeRequirements = type->getArgs();
-  containsParameterized = true;
+  parameterized.push_back(type);
 }
 
 ExistentialLayout TypeBase::getExistentialLayout() {

lib/IRGen/MetadataRequest.cpp

@@ -272,7 +272,7 @@ static bool usesExtendedExistentialMetadata(CanType type) {
   // should turn them into unparameterized protocol types.  If the
   // structure makes it to IRGen, we have to honor that decision that
   // they represent different types.
-  return layout.containsParameterized;
+  return !layout.getParameterizedProtocols().empty();
 }
 
 static std::optional<std::pair<CanExistentialType, /*depth*/ unsigned>>
@@ -2026,7 +2026,7 @@ namespace {
     llvm::Value *emitExistentialTypeMetadata(CanExistentialType type) {
       auto layout = type.getExistentialLayout();
 
-      if (layout.containsParameterized) {
+      if (!layout.getParameterizedProtocols().empty()) {
         return emitExtendedExistentialTypeMetadata(type);
       }