[NFC] Unify helpers for checking for ObjC generics

There were two differently-named and slightly differently-implemented checks on nominal type decls. Clean this up a bit.

Author: beccadax

include/swift/AST/Decl.h

@@ -3979,7 +3979,7 @@ class ClassDecl final : public NominalTypeDecl {
   /// Returns true if the decl uses the Objective-C generics model.
   ///
   /// This is true of imported Objective-C classes.
-  bool usesObjCGenericsModel() const {
+  bool isTypeErasedGenericClass() const {
     return hasClangNode() && isGenericContext() && isObjC();
   }
 

lib/AST/Decl.cpp

@@ -2919,7 +2919,8 @@ bool ValueDecl::isObjCDynamicInGenericClass() const {
   if (!classDecl)
     return false;
 
-  return classDecl->isGenericContext() && !classDecl->usesObjCGenericsModel();
+  return classDecl->isGenericContext()
+             && !classDecl->isTypeErasedGenericClass();
 }
 
 bool ValueDecl::shouldUseObjCMethodReplacement() const {
@@ -4190,7 +4191,7 @@ bool NominalTypeDecl::isTypeErasedGenericClass() const {
   // ObjC classes are type erased.
   // TODO: Unless they have magic methods...
   if (auto clas = dyn_cast<ClassDecl>(this))
-    return clas->hasClangNode() && clas->isGenericContext();
+    return clas->isTypeErasedGenericClass();
   return false;
 }
 

lib/IRGen/GenProto.cpp

@@ -418,7 +418,7 @@ void PolymorphicConvention::considerParameter(SILParameterInfo param,
         // sources of metadata.
         CanType objTy = metatypeTy.getInstanceType();
         if (auto classDecl = objTy->getClassOrBoundGenericClass())
-          if (classDecl->usesObjCGenericsModel())
+          if (classDecl->isTypeErasedGenericClass())
             return;
 
         considerNewTypeSource(MetadataSource::Kind::Metadata,

lib/SIL/IR/SILFunctionType.cpp

@@ -1766,7 +1766,7 @@ static bool isPseudogeneric(SILDeclRef c) {
   if (!dc) return false;
 
   auto classDecl = dc->getSelfClassDecl();
-  return (classDecl && classDecl->usesObjCGenericsModel());
+  return (classDecl && classDecl->isTypeErasedGenericClass());
 }
 
 /// Update the result type given the foreign error convention that we will be

lib/SIL/Utils/DynamicCasts.cpp

@@ -603,12 +603,12 @@ swift::classifyDynamicCast(ModuleDecl *M,
     if (targetClass) {
       // Imported Objective-C generics don't check the generic parameters, which
       // are lost at runtime.
-      if (sourceClass->usesObjCGenericsModel()) {
+      if (sourceClass->isTypeErasedGenericClass()) {
 
         if (sourceClass == targetClass)
           return DynamicCastFeasibility::WillSucceed;
 
-        if (targetClass->usesObjCGenericsModel()) {
+        if (targetClass->isTypeErasedGenericClass()) {
           // If both classes are ObjC generics, the cast may succeed if the
           // classes are related, irrespective of their generic parameters.
 

lib/SIL/Verifier/SILVerifier.cpp

@@ -4030,7 +4030,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
       require(instClass,
               "upcast must convert a class metatype to a class metatype");
 
-      if (instClass->usesObjCGenericsModel()) {
+      if (instClass->isTypeErasedGenericClass()) {
         require(instClass->getDeclaredTypeInContext()
                   ->isBindableToSuperclassOf(opInstTy),
                 "upcast must cast to a superclass or an existential metatype");
@@ -4063,7 +4063,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     auto ToClass = ToTy.getClassOrBoundGenericClass();
     require(ToClass,
             "upcast must convert a class instance to a class type");
-      if (ToClass->usesObjCGenericsModel()) {
+      if (ToClass->isTypeErasedGenericClass()) {
         require(ToClass->getDeclaredTypeInContext()
                   ->isBindableToSuperclassOf(FromTy.getASTType()),
                 "upcast must cast to a superclass or an existential metatype");

lib/Sema/TypeCheckCaptures.cpp

@@ -108,7 +108,7 @@ class FindCapturedVars : public ASTWalker {
         // don't need to visit them.
         if (ObjC) {
           if (auto clas = dyn_cast_or_null<ClassDecl>(ty->getAnyNominal())) {
-            if (clas->usesObjCGenericsModel()) {
+            if (clas->isTypeErasedGenericClass()) {
               return Action::SkipChildren;
             }
           }
@@ -530,7 +530,7 @@ class FindCapturedVars : public ASTWalker {
         return false;
 
       if (auto clas = dyn_cast_or_null<ClassDecl>(toTy->getAnyNominal())) {
-        if (clas->usesObjCGenericsModel()) {
+        if (clas->isTypeErasedGenericClass()) {
           return false;
         }
       }
@@ -658,7 +658,7 @@ void TypeChecker::computeCaptures(AnyFunctionRef AFR) {
   // their context.
   if (AFD && finder.hasGenericParamCaptures()) {
     if (auto Clas = AFD->getParent()->getSelfClassDecl()) {
-      if (Clas->usesObjCGenericsModel()) {
+      if (Clas->isTypeErasedGenericClass()) {
         AFD->diagnose(diag::objc_generic_extension_using_type_parameter);
 
         // If it's possible, suggest adding @objc.

lib/Sema/TypeCheckConstraints.cpp

@@ -1857,7 +1857,7 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
   // classes. This may be necessary to force-fit ObjC APIs that depend on
   // covariance, or for APIs where the generic parameter annotations in the
   // ObjC headers are inaccurate.
-  if (clas && clas->usesObjCGenericsModel()) {
+  if (clas && clas->isTypeErasedGenericClass()) {
     if (fromType->getClassOrBoundGenericClass() == clas)
       return CheckedCastKind::ValueCast;
   }

lib/Sema/TypeCheckDeclObjC.cpp

@@ -553,7 +553,7 @@ static bool checkObjCInExtensionContext(const ValueDecl *value,
                 ->getModuleContext()
                 ->isImplicitDynamicEnabled())
           return false;
-        if (!classDecl->usesObjCGenericsModel()) {
+        if (!classDecl->isTypeErasedGenericClass()) {
           softenIfAccessNote(value, reason.getAttr(),
             value->diagnose(diag::objc_in_generic_extension,
                             classDecl->isGeneric())

lib/Sema/TypeCheckProtocol.cpp

@@ -1993,7 +1993,7 @@ checkIndividualConformance(NormalProtocolConformance *conformance,
     if (auto ext = dyn_cast<ExtensionDecl>(DC)) {
       if (auto classDecl = ext->getSelfClassDecl()) {
         if (classDecl->isGenericContext()) {
-          if (!classDecl->usesObjCGenericsModel()) {
+          if (!classDecl->isTypeErasedGenericClass()) {
             C.Diags.diagnose(ComplainLoc,
                              diag::objc_protocol_in_generic_extension,
                              classDecl->isGeneric(), T, ProtoType);
@@ -2014,7 +2014,7 @@ checkIndividualConformance(NormalProtocolConformance *conformance,
     // types for any obj-c ones.
     while (nestedType) {
       if (auto clas = nestedType->getClassOrBoundGenericClass()) {
-        if (clas->usesObjCGenericsModel()) {
+        if (clas->isTypeErasedGenericClass()) {
           C.Diags.diagnose(ComplainLoc,
                            diag::objc_generics_cannot_conditionally_conform, T,
                            ProtoType);
@@ -3014,7 +3014,7 @@ bool ConformanceChecker::checkObjCTypeErasedGenerics(
   auto classDecl = Adoptee->getClassOrBoundGenericClass();
   if (!classDecl) return false;
 
-  if (!classDecl->usesObjCGenericsModel()) return false;
+  if (!classDecl->isTypeErasedGenericClass()) return false;
 
   // Concrete types are okay.
   if (!type->getCanonicalType()->hasTypeParameter()) return false;