AST: Hack around edge case due to broken abstract conformance representation

A substitution map might store an abstract conformance even if the
replacement type is an archetype that conforms concretely via a
superclass requirement.

This is because when we build the substitution map, if the archetype
is represented by a type parameter, we don't have enough information
to know if it will conform abstractly or concretely.

Author: slavapestov

lib/AST/SubstitutionMap.cpp

@@ -638,6 +638,9 @@ SubstitutionMap::combineSubstitutionMaps(SubstitutionMap firstSubMap,
       // Some combination of storing substitution maps in BoundGenericTypes
       // as well as for method overrides would solve this, but for now, just
       // punt to module lookup.
+      if (substType->isTypeParameter())
+        return ProtocolConformanceRef(proto);
+
       return proto->getParentModule()->lookupConformance(substType, proto);
     });
 }

lib/AST/Type.cpp

@@ -4428,10 +4428,12 @@ operator()(CanType dependentType, Type conformingReplacementType,
 ProtocolConformanceRef LookUpConformanceInSubstitutionMap::
 operator()(CanType dependentType, Type conformingReplacementType,
            ProtocolDecl *conformedProtocol) const {
-  // Lookup conformances for opened existential.
-  if (conformingReplacementType->isOpenedExistential()) {
+  // Lookup conformances for archetypes that conform concretely
+  // via a superclass.
+  if (auto archetypeType = conformingReplacementType->getAs<ArchetypeType>()) {
     return conformedProtocol->getModuleContext()->lookupConformance(
-        conformingReplacementType, conformedProtocol);
+        conformingReplacementType, conformedProtocol,
+        /*allowMissing=*/true);
   }
   return Subs.lookupConformance(dependentType, conformedProtocol);
 }

test/SILGen/vtable_generic_signature.swift

@@ -3,9 +3,11 @@
 
 protocol P {}
 protocol Q : P {}
+class C : P {}
 
 class ConcreteBase {
   func f<U : Q>(_: U) {}
+  func g<U : C>(_: U) {}
 }
 
 class ConcreteDerivedFromConcreteBase : ConcreteBase {
@@ -37,6 +39,10 @@ func call<T, U : P>(_ t: T, _ u: U) {
   GenericDerivedFromGenericBase<T>().f(u)
 }
 
+class ConcreteDerived: ConcreteBase {
+  override func g<U : P>(_: U) {}
+}
+
 // All the vtable thunks should traffic in <U where U : Q>, because that's
 // what the base method declares.
 
@@ -47,19 +53,22 @@ func call<T, U : P>(_ t: T, _ u: U) {
 
 // CHECK-LABEL: sil_vtable ConcreteBase {
 // CHECK-NEXT:   #ConcreteBase.f: <U where U : Q> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature12ConcreteBaseC1fyyxAA1QRzlF
+// CHECK-NEXT:   #ConcreteBase.g: <U where U : C> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature12ConcreteBaseC1gyyxAA1CCRbzlF
 // CHECK-NEXT:   #ConcreteBase.init!allocator: (ConcreteBase.Type) -> () -> ConcreteBase : @$s24vtable_generic_signature12ConcreteBaseCACycfC
 // CHECK-NEXT:   #ConcreteBase.deinit!deallocator: @$s24vtable_generic_signature12ConcreteBaseCfD
 // CHECK-NEXT: }
 
 // CHECK-LABEL: sil_vtable ConcreteDerivedFromConcreteBase {
 // CHECK-NEXT:   #ConcreteBase.f: <U where U : Q> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature019ConcreteDerivedFromD4BaseC1fyyxAA1PRzlFAA0dG0CADyyxAA1QRzlFTV [override]
+// CHECK-NEXT:   #ConcreteBase.g: <U where U : C> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature12ConcreteBaseC1gyyxAA1CCRbzlF
 // CHECK-NEXT:   #ConcreteBase.init!allocator: (ConcreteBase.Type) -> () -> ConcreteBase : @$s24vtable_generic_signature019ConcreteDerivedFromD4BaseCACycfC [override]
 // CHECK-NEXT:   #ConcreteDerivedFromConcreteBase.f: <U where U : P> (ConcreteDerivedFromConcreteBase) -> (U) -> () : @$s24vtable_generic_signature019ConcreteDerivedFromD4BaseC1fyyxAA1PRzlF
 // CHECK-NEXT:   #ConcreteDerivedFromConcreteBase.deinit!deallocator: @$s24vtable_generic_signature019ConcreteDerivedFromD4BaseCfD
 // CHECK-NEXT: }
 
 // CHECK-LABEL: sil_vtable GenericDerivedFromConcreteBase {
 // CHECK-NEXT:   #ConcreteBase.f: <U where U : Q> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature30GenericDerivedFromConcreteBaseC1fyyqd__AA1PRd__lFAA0gH0CADyyxAA1QRzlFTV [override]
+// CHECK-NEXT:   #ConcreteBase.g: <U where U : C> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature12ConcreteBaseC1gyyxAA1CCRbzlF
 // CHECK-NEXT:   #ConcreteBase.init!allocator: (ConcreteBase.Type) -> () -> ConcreteBase : @$s24vtable_generic_signature30GenericDerivedFromConcreteBaseCACyxGycfC [override]
 // CHECK-NEXT:   #GenericDerivedFromConcreteBase.f: <T><U where U : P> (GenericDerivedFromConcreteBase<T>) -> (U) -> () : @$s24vtable_generic_signature30GenericDerivedFromConcreteBaseC1fyyqd__AA1PRd__lF
 // CHECK-NEXT:   #GenericDerivedFromConcreteBase.deinit!deallocator: @$s24vtable_generic_signature30GenericDerivedFromConcreteBaseCfD
@@ -84,3 +93,11 @@ func call<T, U : P>(_ t: T, _ u: U) {
 // CHECK-NEXT:   #GenericDerivedFromGenericBase.f: <T><U where U : P> (GenericDerivedFromGenericBase<T>) -> (U) -> () : @$s24vtable_generic_signature018GenericDerivedFromD4BaseC1fyyqd__AA1PRd__lF
 // CHECK-NEXT:   #GenericDerivedFromGenericBase.deinit!deallocator: @$s24vtable_generic_signature018GenericDerivedFromD4BaseCfD
 // CHECK-NEXT: }
+
+// CHECK-LABEL: sil_vtable ConcreteDerived {
+// CHECK-NEXT:   #ConcreteBase.f: <U where U : Q> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature12ConcreteBaseC1fyyxAA1QRzlF [inherited]
+// CHECK-NEXT:   #ConcreteBase.g: <U where U : C> (ConcreteBase) -> (U) -> () : @$s24vtable_generic_signature15ConcreteDerivedC1gyyxAA1PRzlFAA0D4BaseCADyyxAA1CCRbzlFTV [override]
+// CHECK-NEXT:   #ConcreteBase.init!allocator: (ConcreteBase.Type) -> () -> ConcreteBase : @$s24vtable_generic_signature15ConcreteDerivedCACycfC [override]
+// CHECK-NEXT:   #ConcreteDerived.g: <U where U : P> (ConcreteDerived) -> (U) -> () : @$s24vtable_generic_signature15ConcreteDerivedC1gyyxAA1PRzlF
+// CHECK-NEXT:   #ConcreteDerived.deinit!deallocator: @$s24vtable_generic_signature15ConcreteDerivedCfD  // ConcreteDerived.__deallocating_deinit
+// CHECK-NEXT: }