Allow the mangler to disregard inverses

Author: Azoy

include/swift/AST/ExistentialLayout.h

@@ -125,7 +125,11 @@ struct ExistentialLayout {
   /// Whether this existential needs to have an extended existential shape. This
   /// is relevant for the mangler to mangle as a symbolic link where possible
   /// and for IRGen directly emitting some existentials.
-  bool needsExtendedShape() const;
+  ///
+  /// If 'allowInverses' is false, then regardless of if this existential layout
+  /// has inverse requirements those will not influence the need for having a
+  /// shape.
+  bool needsExtendedShape(bool allowInverses = true) const;
 
 private:
   SmallVector<ProtocolDecl *, 4> protocols;

lib/AST/ASTMangler.cpp

@@ -1613,19 +1613,17 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
       // ExtendedExistentialTypeShapes consider existential metatypes to
       // be part of the existential, so if we're symbolically referencing
       // shapes, we need to handle that at this level.
-      if (EMT->getExistentialLayout().needsExtendedShape()) {
+      if (EMT->getExistentialLayout().needsExtendedShape(AllowInverses)) {
         auto referent = SymbolicReferent::forExtendedExistentialTypeShape(EMT);
         if (canSymbolicReference(referent)) {
           appendSymbolicExtendedExistentialType(referent, EMT, sig, forDecl);
           return;
         }
-      }
 
-      if (EMT->getInstanceType()->isExistentialType() &&
-          EMT->hasParameterizedExistential())
         appendConstrainedExistential(EMT->getInstanceType(), sig, forDecl);
-      else
+      } else {
         appendType(EMT->getInstanceType(), sig, forDecl);
+      }
 
       if (EMT->hasRepresentation()) {
         appendOperator("Xm",
@@ -1678,8 +1676,7 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
           return appendType(strippedTy, sig, forDecl);
       }
 
-      if (PCT->hasParameterizedExistential()
-          || (PCT->hasInverse() && AllowInverses))
+      if (PCT->getExistentialLayout().needsExtendedShape(AllowInverses))
         return appendConstrainedExistential(PCT, sig, forDecl);
 
       // We mangle ProtocolType and ProtocolCompositionType using the
@@ -1693,7 +1690,8 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
 
     case TypeKind::Existential: {
       auto *ET = cast<ExistentialType>(tybase);
-      if (ET->getExistentialLayout().needsExtendedShape()) {
+
+      if (ET->getExistentialLayout().needsExtendedShape(AllowInverses)) {
         auto referent = SymbolicReferent::forExtendedExistentialTypeShape(ET);
         if (canSymbolicReference(referent)) {
           appendSymbolicExtendedExistentialType(referent, ET, sig, forDecl);
@@ -1703,6 +1701,7 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
         return appendConstrainedExistential(ET->getConstraintType(), sig,
                                             forDecl);
       }
+
       return appendType(ET->getConstraintType(), sig, forDecl);
     }
 

lib/AST/Type.cpp

@@ -435,11 +435,11 @@ Type ExistentialLayout::getSuperclass() const {
   return Type();
 }
 
-bool ExistentialLayout::needsExtendedShape() const {
+bool ExistentialLayout::needsExtendedShape(bool allowInverses) const {
   if (!getParameterizedProtocols().empty())
     return true;
 
-  if (hasInverses())
+  if (allowInverses && hasInverses())
     return true;
 
   return false;