Add a Facility to Compute an Opened Archetype's Self Parameter

Author: CodaFi

include/swift/AST/Types.h

@@ -5746,6 +5746,15 @@ class OpenedArchetypeType final : public ArchetypeType,
          ArrayRef<ProtocolDecl *> conformsTo, Type superclass,
          LayoutConstraint layout);
 
+public:
+  /// Compute the parameter that serves as the \c Self type for an opened
+  /// archetype from the given declaration context.
+  ///
+  /// For protocol extensions, this type is the context's \c Self type. For
+  /// all other contexts, this type is a generic parameter one level deeper
+  /// than the deepest generic context depth.
+  static Type getSelfInterfaceTypeFromContext(const DeclContext *useDC);
+
 public:
   /// Get or create an archetype that represents the opened type
   /// of an existential value.

lib/AST/ASTContext.cpp

@@ -4423,9 +4423,8 @@ CanTypeWrapper<OpenedArchetypeType> OpenedArchetypeType::getNew(
     ArrayRef<ProtocolDecl *> conformsTo, Type superclass,
     LayoutConstraint layout) {
   // FIXME: It'd be great if all of our callers could submit interface types.
-  // But the constraint solver submits archetypes when trying to issue checks
-  // against members of existential types. For now, we'll work around them by
-  // forcing an interface type.
+  // But the constraint solver submits archetypes when e.g. trying to issue
+  // checks against members of existential types.
   //  assert((!superclass || !superclass->hasArchetype())
   //         && "superclass must be interface type");
   auto arena = AllocationArena::Permanent;
@@ -4444,11 +4443,9 @@ CanTypeWrapper<OpenedArchetypeType> OpenedArchetypeType::getNew(
 CanTypeWrapper<OpenedArchetypeType>
 OpenedArchetypeType::get(CanType existential, const DeclContext *useDC,
                          Optional<UUID> knownID) {
-  Type interfaceType = GenericTypeParamType::get(
-      /*isTypeSequence=*/false,
-      /*depth*/ useDC->getGenericContextDepth() + 1, /*index*/ 0,
-      existential->getASTContext());
-  return get(existential, interfaceType, useDC, knownID);
+  return get(existential,
+             OpenedArchetypeType::getSelfInterfaceTypeFromContext(useDC),
+             useDC, knownID);
 }
 
 CanOpenedArchetypeType OpenedArchetypeType::get(CanType existential,
@@ -4511,10 +4508,9 @@ CanType OpenedArchetypeType::getAny(CanType existential, Type interfaceType,
 
 CanType OpenedArchetypeType::getAny(CanType existential,
                                     const DeclContext *useDC) {
-  Type interfaceType = GenericTypeParamType::get(
-      /*isTypeSequence=*/false, useDC->getGenericContextDepth() + 1, 0,
-      existential->getASTContext());
-  return getAny(existential, interfaceType, useDC);
+  return getAny(existential,
+                OpenedArchetypeType::getSelfInterfaceTypeFromContext(useDC),
+                useDC);
 }
 
 void SubstitutionMap::Storage::Profile(
@@ -5191,6 +5187,18 @@ CanGenericSignature ASTContext::getSingleGenericParameterSignature() const {
   return canonicalSig;
 }
 
+Type OpenedArchetypeType::getSelfInterfaceTypeFromContext(const DeclContext *useDC) {
+  auto typeContext = useDC->getInnermostTypeContext();
+  if (typeContext && typeContext->getSelfProtocolDecl()) {
+    return typeContext->getProtocolSelfType();
+  } else {
+    return GenericTypeParamType::get(
+        /*isTypeSequence=*/false,
+        /*depth*/ useDC->getGenericContextDepth() + 1, /*index*/ 0,
+        useDC->getASTContext());
+  }
+}
+
 CanGenericSignature
 ASTContext::getOpenedArchetypeSignature(Type type, const DeclContext *useDC) {
   assert(type->isExistentialType());
@@ -5218,14 +5226,21 @@ ASTContext::getOpenedArchetypeSignature(Type type, const DeclContext *useDC) {
   if (found != getImpl().ExistentialSignatures.end())
     return found->second;
 
-  auto depth = useDC->getGenericContextDepth() + 1;
-  auto genericParam =
-      GenericTypeParamType::get(/*type sequence*/ false,
-                                /*depth*/ depth, /*index*/ 0, *this);
+  GenericSignature outerSignature;
+  auto *typeContext = useDC->getInnermostTypeContext();
+  if (typeContext && typeContext->getSelfProtocolDecl()) {
+    outerSignature = GenericSignature();
+  } else {
+    outerSignature = useDC->getGenericSignatureOfContext();
+  }
+
+  auto genericParam = OpenedArchetypeType::getSelfInterfaceTypeFromContext(useDC)
+                        ->getCanonicalType()->getAs<GenericTypeParamType>();
+
   Requirement requirement(RequirementKind::Conformance, genericParam,
                           constraint);
   auto genericSig = buildGenericSignature(
-      *this, useDC->getGenericSignatureOfContext().getCanonicalSignature(),
+      *this, outerSignature.getCanonicalSignature(),
       {genericParam}, {requirement});
 
   CanGenericSignature canGenericSig(genericSig);

lib/AST/Decl.cpp

@@ -2926,7 +2926,7 @@ CanType ValueDecl::getOverloadSignatureType() const {
                                     /*topLevelFunction=*/true, isMethod,
                                     /*isInitializer=*/isa<ConstructorDecl>(afd),
                                     getNumCurryLevels())
-        ->getMinimalCanonicalType(afd);
+        ->getCanonicalType();
   }
 
   if (isa<AbstractStorageDecl>(this)) {
@@ -2942,22 +2942,22 @@ CanType ValueDecl::getOverloadSignatureType() const {
                                    /*topLevelFunction=*/true,
                                    /*isMethod=*/false,
                                    /*isInitializer=*/false, getNumCurryLevels())
-              ->getMinimalCanonicalType(getDeclContext());
+              ->getCanonicalType();
     }
 
     // We want to curry the default signature type with the 'self' type of the
     // given context (if any) in order to ensure the overload signature type
     // is unique across different contexts, such as between a protocol extension
     // and struct decl.
     return defaultSignatureType->addCurriedSelfType(getDeclContext())
-        ->getMinimalCanonicalType(getDeclContext());
+        ->getCanonicalType();
   }
 
   if (isa<EnumElementDecl>(this)) {
     auto mappedType = mapSignatureFunctionType(
         getASTContext(), getInterfaceType(), /*topLevelFunction=*/false,
         /*isMethod=*/false, /*isInitializer=*/false, getNumCurryLevels());
-    return mappedType->getMinimalCanonicalType(getDeclContext());
+    return mappedType->getCanonicalType();
   }
 
   // Note: If you add more cases to this function, you should update the

lib/AST/Type.cpp

@@ -4017,7 +4017,12 @@ CanType ProtocolCompositionType::getMinimalCanonicalType(
   Type superclass;
   llvm::SmallVector<Type, 2> MinimalMembers;
   bool MinimalHasExplicitAnyObject = false;
+  auto ifaceTy = OpenedArchetypeType::getSelfInterfaceTypeFromContext(useDC);
   for (const auto &Req : Reqs) {
+    if (!Req.getFirstType()->isEqual(ifaceTy)) {
+      continue;
+    }
+
     switch (Req.getKind()) {
     case RequirementKind::Superclass:
       assert((!superclass || superclass->isEqual(Req.getSecondType()))
@@ -4035,7 +4040,7 @@ CanType ProtocolCompositionType::getMinimalCanonicalType(
     }
   }
 
-  // Ensure any superclass bounds appears first regardless of its order among
+  // Ensure superclass bounds appear first regardless of their order among
   // the signature's requirements.
   if (superclass)
     MinimalMembers.insert(MinimalMembers.begin(), superclass->getCanonicalType());

lib/SIL/Utils/MemoryLocations.cpp

@@ -200,7 +200,7 @@ void MemoryLocations::analyzeLocation(SILValue loc) {
   SubLocationMap subLocationMap;
   if (!analyzeLocationUsesRecursively(loc, currentLocIdx, collectedVals,
                                       subLocationMap)) {
-    //    locations.truncate(currentLocIdx);
+    locations.truncate(currentLocIdx);
     for (SILValue V : collectedVals) {
       addr2LocIdx.erase(V);
     }

lib/Sema/ConstraintSystem.cpp

@@ -6020,7 +6020,7 @@ void ConstraintSystem::maybeProduceFallbackDiagnostic(
 /// Because opened archetypes are not part of the surface language, these
 /// constraints render the member inaccessible.
 static bool doesMemberHaveUnfulfillableConstraintsWithExistentialBase(
-    Type baseTy, const ValueDecl *member) {
+    Type baseTy, const ValueDecl *member, const DeclContext *useDC) {
   const auto sig =
       member->getInnermostDeclContext()->getGenericSignatureOfContext();
 
@@ -6057,7 +6057,7 @@ static bool doesMemberHaveUnfulfillableConstraintsWithExistentialBase(
       return Action::Stop;
     }
   } isDependentOnSelfWalker(member->getASTContext().getOpenedArchetypeSignature(
-      baseTy, member->getDeclContext()));
+      baseTy, useDC));
 
   for (const auto &req : sig.getRequirements()) {
     switch (req.getKind()) {
@@ -6099,8 +6099,13 @@ bool ConstraintSystem::isMemberAvailableOnExistential(
 
   // If the type of the member references 'Self' or a 'Self'-rooted associated
   // type in non-covariant position, we cannot reference the member.
+  //
+  // N.B. We pass the module context because this check does not care about the
+  // the actual signature of the opened archetype in context, rather it cares
+  // about whether you can "hold" `baseTy.member` properly in the abstract.
   const auto info = member->findExistentialSelfReferences(
-      baseTy, DC, /*treatNonResultCovariantSelfAsInvariant=*/false);
+      baseTy, DC->getModuleScopeContext(),
+      /*treatNonResultCovariantSelfAsInvariant=*/false);
   if (info.selfRef > TypePosition::Covariant ||
       info.assocTypeRef > TypePosition::Covariant) {
     return false;
@@ -6113,7 +6118,8 @@ bool ConstraintSystem::isMemberAvailableOnExistential(
   }
 
   if (doesMemberHaveUnfulfillableConstraintsWithExistentialBase(baseTy,
-                                                                member)) {
+                                                                member,
+                                                                DC)) {
     return false;
   }
 

test/SILGen/witnesses_class.swift

@@ -84,9 +84,9 @@ class UsesDefaults<X : Barable> : HasDefaults {}
 
 // Invariant Self, since type signature contains an associated type:
 
-// CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyxGAA03HasD0A2aEP16hasDefaultTakesTyy1TQzFTW : $@convention(witness_method: HasDefaults) <τ_0_0 where τ_0_0 : Barable> (@in_guaranteed UsesDefaults<τ_0_0>, @in_guaranteed UsesDefaults<τ_0_0>) -> ()
+// CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyqd__GAA03HasD0A2aEP16hasDefaultTakesTyy1TQzFTW : $@convention(witness_method: HasDefaults) <τ_0_0><τ_1_0 where τ_0_0 : UsesDefaults<τ_1_0>, τ_1_0 : Barable> (@in_guaranteed UsesDefaults<τ_1_0>, @in_guaranteed τ_0_0) -> ()
 // CHECK: [[FN:%.*]] = function_ref @$s15witnesses_class11HasDefaultsPAAE16hasDefaultTakesTyy1TQzF : $@convention(method) <τ_0_0 where τ_0_0 : HasDefaults> (@in_guaranteed τ_0_0.T, @in_guaranteed τ_0_0) -> ()
-// CHECK: apply [[FN]]<UsesDefaults<τ_0_0>>(
+// CHECK: apply [[FN]]<τ_0_0>(
 // CHECK: return
 
 // Covariant Self:
@@ -98,9 +98,9 @@ class UsesDefaults<X : Barable> : HasDefaults {}
 
 // Invariant Self, since type signature contains an associated type:
 
-// CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyxGAA03HasD0A2aEP23hasDefaultGenericTakesTyy1TQz_qd__tAA7FooableRd__lFTW : $@convention(witness_method: HasDefaults) <τ_0_0 where τ_0_0 : Barable><τ_1_0 where τ_1_0 : Fooable> (@in_guaranteed UsesDefaults<τ_0_0>, @guaranteed τ_1_0, @in_guaranteed UsesDefaults<τ_0_0>) -> ()
+// CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyqd__GAA03HasD0A2aEP23hasDefaultGenericTakesTyy1TQz_qd__tAA7FooableRd__lFTW : $@convention(witness_method: HasDefaults) <τ_0_0><τ_1_0 where τ_0_0 : UsesDefaults<τ_1_0>, τ_1_0 : Barable><τ_2_0 where τ_2_0 : Fooable> (@in_guaranteed UsesDefaults<τ_1_0>, @guaranteed τ_2_0, @in_guaranteed τ_0_0) -> ()
 // CHECK: [[FN:%.*]] = function_ref @$s15witnesses_class11HasDefaultsPAAE23hasDefaultGenericTakesTyy1TQz_qd__tAA7FooableRd__lF : $@convention(method) <τ_0_0 where τ_0_0 : HasDefaults><τ_1_0 where τ_1_0 : Fooable> (@in_guaranteed τ_0_0.T, @guaranteed τ_1_0, @in_guaranteed τ_0_0) -> ()
-// CHECK: apply [[FN]]<UsesDefaults<τ_0_0>, τ_1_0>(
+// CHECK: apply [[FN]]<τ_0_0, τ_2_0>(
 // CHECK: return
 
 protocol ReturnsCovariantSelf {