fix: Catalyst crashes

* Default initialize pointers
* Gracefully handle invalid `decl`s and show appropriate errors in output
* Check for `getDefinition` returning `nullptr`
* Fallback to enum's declaration if there's no definition

Author: mbektchiev

src/Meta/MetaEntities.h

@@ -106,8 +106,8 @@ class Meta {
     std::string name;
     std::string jsName;
     std::string fileName;
-    clang::Module* module;
-    const clang::Decl* declaration;
+    clang::Module* module = nullptr;
+    const clang::Decl* declaration = nullptr;
 
     // Availability
     Version introducedIn = UNKNOWN_VERSION;
@@ -185,8 +185,8 @@ class PropertyMeta : public Meta {
         this->type = MetaType::Property;
     }
 
-    MethodMeta* getter;
-    MethodMeta* setter;
+    MethodMeta* getter = nullptr;
+    MethodMeta* setter = nullptr;
 
     virtual void visit(MetaVisitor* visitor) override;
 };
@@ -279,7 +279,7 @@ class EnumConstantMeta : public Meta {
 
     std::string value;
 
-    bool isScoped;
+    bool isScoped = false;
 
     virtual void visit(MetaVisitor* visitor) override;
 };
@@ -310,8 +310,8 @@ class VarMeta : public Meta {
         this->type = MetaType::Var;
     }
 
-    Type* signature;
-    bool hasValue;
+    Type* signature = nullptr;
+    bool hasValue = false;
     std::string value;
 
     virtual void visit(MetaVisitor* visitor) override;

src/Meta/MetaFactory.cpp

@@ -78,6 +78,13 @@ void resetMetaAndAddToMap(std::unique_ptr<Meta>& metaPtrRef, MetaToDeclMap& meta
         metaPtrRef.reset(new T());
         metaToDecl[metaPtrRef.get()] = &decl;
     }
+    
+    if (decl.isInvalidDecl()) {
+        std::string declDump;
+        llvm::raw_string_ostream os(declDump);
+        decl.dump(os);
+        throw MetaCreationException(metaPtrRef.get(), CreationException::constructMessage("Invalid decl.", os.str()), true);
+    }
 }
 
 Meta* MetaFactory::create(const clang::Decl& decl, bool resetCached /* = false*/)
@@ -347,7 +354,7 @@ void MetaFactory::createFromInterface(const clang::ObjCInterfaceDecl& interface,
 
     // set base interface
     clang::ObjCInterfaceDecl* super = interface.getSuperClass();
-    interfaceMeta.base = (super == nullptr) ? nullptr : &this->create(*super->getDefinition())->as<InterfaceMeta>();
+    interfaceMeta.base = (super == nullptr || super->getDefinition() == nullptr) ? nullptr : &this->create(*super->getDefinition())->as<InterfaceMeta>();
 }
 
 void MetaFactory::createFromProtocol(const clang::ObjCProtocolDecl& protocol, ProtocolMeta& protocolMeta)
@@ -589,7 +596,8 @@ void MetaFactory::populateBaseClassMetaFields(const clang::ObjCContainerDecl& de
 {
     for (clang::ObjCProtocolDecl* protocol : this->getProtocols(&decl)) {
         Meta* protocolMeta;
-        if (this->tryCreate(*protocol->getDefinition(), &protocolMeta)) {
+        
+        if (protocol->getDefinition() != nullptr && this->tryCreate(*protocol->getDefinition(), &protocolMeta)) {
             baseClass.protocols.push_back(&protocolMeta->as<ProtocolMeta>());
         }
     }

src/Meta/TypeFactory.cpp

@@ -356,7 +356,8 @@ shared_ptr<Type> TypeFactory::createFromPointerType(const clang::PointerType* ty
 shared_ptr<Type> TypeFactory::createFromEnumType(const clang::EnumType* type)
 {
     Type* innerType = this->create(type->getDecl()->getIntegerType()).get();
-    EnumMeta* enumMeta = &this->_metaFactory->create(*type->getDecl()->getDefinition())->as<EnumMeta>();
+    auto& enumDecl = type->getDecl()->getDefinition() ? *type->getDecl()->getDefinition() : *type->getDecl();
+    EnumMeta* enumMeta = &this->_metaFactory->create(enumDecl)->as<EnumMeta>();
     return make_shared<EnumType>(innerType, enumMeta);
 }