Fix order of adding keys for typedefs (#557)

This fixes brunsli: `BrotliDecoderState` is a typedef over `struct
BrotliDecoderStateStruct` and `struct BrotliDecoderStateStruct` is
forward declared in another TU.

Author: lucic71

cpp2rust/converter/rules/rules_loader.cpp

@@ -159,6 +159,7 @@ class RuleUsageCollector
     AddKey(TypeKey(type));
     if (const auto *alias =
             llvm::dyn_cast<clang::TypedefType>(type.getTypePtr())) {
+      AddKey(DeclKey(alias->getDecl()));
       if (const auto *record = llvm::dyn_cast<clang::RecordDecl>(
               alias->getDecl()->getDeclContext())) {
         AddKey(ClassKey(record));

cpp2rust/rule_preprocessing/cpp_rule_indexer.cpp

@@ -215,12 +215,18 @@ std::string ExprKey(clang::ASTContext &ctx, const clang::Decl *rule) {
 
 std::string TypeKey(const clang::TypedefNameDecl *rule) {
   auto type = rule->getUnderlyingType();
+  for (auto pointee = type;; pointee = pointee->getPointeeType()) {
+    if (auto alias = pointee->getAs<clang::TypedefType>();
+        alias && !pointee->isDependentType()) {
+      return RulesLoader::DeclKey(alias->getDecl());
+    }
+    if (!pointee->isPointerType() && !pointee->isReferenceType()) {
+      break;
+    }
+  }
   if (auto key = RulesLoader::TypeKey(type); !key.empty()) {
     return key;
   }
-  if (!type->isDependentType() && type->getAs<clang::TypedefType>()) {
-    return RulesLoader::TypeKey(type);
-  }
   while (type->isPointerType() || type->isReferenceType()) {
     type = type->getPointeeType();
   }