Merge pull request #41742 from slavapestov/fix-find-existential-self-references

AST: Fix mistake with generic signature in findExistentialSelfReferences()

Author: slavapestov

include/swift/AST/Decl.h

@@ -2693,8 +2693,7 @@ class ValueDecl : public Decl {
   /// property, or the uncurried result type of a method/subscript, e.g.
   /// '() -> () -> Self'.
   GenericParameterReferenceInfo findExistentialSelfReferences(
-      Type baseTy, const DeclContext *useDC,
-      bool treatNonResultCovariantSelfAsInvariant) const;
+      Type baseTy, bool treatNonResultCovariantSelfAsInvariant) const;
 };
 
 /// This is a common base class for declarations which declare a type.

lib/AST/Decl.cpp

@@ -4085,9 +4085,9 @@ GenericParameterReferenceInfo swift::findGenericParameterReferences(
 }
 
 GenericParameterReferenceInfo ValueDecl::findExistentialSelfReferences(
-    Type baseTy, const DeclContext *useDC,
-    bool treatNonResultCovariantSelfAsInvariant) const {
+    Type baseTy, bool treatNonResultCovariantSelfAsInvariant) const {
   assert(baseTy->isExistentialType());
+  assert(!baseTy->hasTypeParameter());
 
   // Types never refer to 'Self'.
   if (isa<TypeDecl>(this))
@@ -4099,9 +4099,12 @@ GenericParameterReferenceInfo ValueDecl::findExistentialSelfReferences(
   if (type->hasError())
     return GenericParameterReferenceInfo();
 
-  const auto sig =
-      getASTContext().getOpenedArchetypeSignature(baseTy,
-                                                  useDC->getGenericSignatureOfContext());
+  // Note: a non-null GenericSignature would violate the invariant that
+  // the protocol 'Self' type referenced from the requirement's interface
+  // type is the same as the existential 'Self' type.
+  auto sig = getASTContext().getOpenedArchetypeSignature(baseTy,
+      GenericSignature());
+
   auto genericParam = sig.getGenericParams().front();
   return findGenericParameterReferences(
       this, sig, genericParam, treatNonResultCovariantSelfAsInvariant, None);

lib/Sema/ConstraintSystem.cpp

@@ -6107,7 +6107,7 @@ bool ConstraintSystem::isMemberAvailableOnExistential(
   // 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->getModuleScopeContext(),
+      baseTy,
       /*treatNonResultCovariantSelfAsInvariant=*/false);
   if (info.selfRef > TypePosition::Covariant ||
       info.assocTypeRef > TypePosition::Covariant) {

lib/Sema/TypeCheckDecl.cpp

@@ -681,7 +681,7 @@ ExistentialRequiresAnyRequest::evaluate(Evaluator &evaluator,
     // For value members, look at their type signatures.
     if (auto valueMember = dyn_cast<ValueDecl>(member)) {
       const auto info = valueMember->findExistentialSelfReferences(
-          decl->getDeclaredInterfaceType(), decl,
+          decl->getDeclaredInterfaceType(),
           /*treatNonResultCovariantSelfAsInvariant=*/false);
       if (info.selfRef > TypePosition::Covariant || info.assocTypeRef) {
         return true;

lib/Sema/TypeCheckProtocol.cpp

@@ -1043,7 +1043,7 @@ swift::matchWitness(WitnessChecker::RequirementEnvironmentCache &reqEnvCache,
         // the default witness for 'Collection.Iterator', which is defined
         // as 'IndexingIterator<Self>'.
         const auto selfRefInfo = req->findExistentialSelfReferences(
-            proto->getDeclaredInterfaceType(), dc,
+            proto->getDeclaredInterfaceType(),
             /*treatNonResultCovariantSelfAsInvariant=*/true);
         if (!selfRefInfo.assocTypeRef) {
           covariantSelf = classDecl;
@@ -4065,7 +4065,7 @@ void ConformanceChecker::checkNonFinalClassWitness(ValueDecl *requirement,
   // Check whether this requirement uses Self in a way that might
   // prevent conformance from succeeding.
   const auto selfRefInfo = requirement->findExistentialSelfReferences(
-      Proto->getDeclaredInterfaceType(), DC,
+      Proto->getDeclaredInterfaceType(),
       /*treatNonResultCovariantSelfAsInvariant=*/true);
 
   if (selfRefInfo.selfRef == TypePosition::Invariant) {

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_class12UsesDefaultsCyqd__GAA03HasD0A2aEP16hasDefaultTakesTyy1TQzFTW : $@convention(witness_method: HasDefaults) <τ_0_0><τ_1_0 where τ_0_0 : UsesDefaults<τ_1_0>, τ_1_0 : Barable> (@in_guaranteed UsesDefaults<τ_1_0>, @in_guaranteed τ_0_0) -> ()
+// CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyxGAA03HasD0A2aEP16hasDefaultTakesTyy1TQzFTW : $@convention(witness_method: HasDefaults) <τ_0_0 where τ_0_0 : Barable> (@in_guaranteed UsesDefaults<τ_0_0>, @in_guaranteed UsesDefaults<τ_0_0>) -> ()
 // CHECK: [[FN:%.*]] = function_ref @$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]]<τ_0_0>(
+// CHECK: apply [[FN]]<UsesDefaults<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_class12UsesDefaultsCyqd__GAA03HasD0A2aEP23hasDefaultGenericTakesTyy1TQz_qd__tAA7FooableRd__lFTW : $@convention(witness_method: HasDefaults) <τ_0_0><τ_1_0 where τ_0_0 : UsesDefaults<τ_1_0>, τ_1_0 : Barable><τ_2_0 where τ_2_0 : Fooable> (@in_guaranteed UsesDefaults<τ_1_0>, @guaranteed τ_2_0, @in_guaranteed τ_0_0) -> ()
+// // CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s15witnesses_class12UsesDefaultsCyxGAA03HasD0A2aEP23hasDefaultGenericTakesTyy1TQz_qd__tAA7FooableRd__lFTW : $@convention(witness_method: HasDefaults) <τ_0_0 where τ_0_0 : Barable><τ_1_0 where τ_1_0 : Fooable> (@in_guaranteed UsesDefaults<τ_0_0>, @guaranteed τ_1_0, @in_guaranteed UsesDefaults<τ_0_0>) -> ()
 // CHECK: [[FN:%.*]] = function_ref @$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]]<τ_0_0, τ_2_0>(
+// CHECK: apply [[FN]]<UsesDefaults<τ_0_0>, τ_1_0>(
 // CHECK: return
 
 protocol ReturnsCovariantSelf {