[clang-tools-extra] [clang-doc] Clean up implementation with better casting (PR #202060)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi updated https://github.com/llvm/llvm-project/pull/202060

>From 048c7f87e7ab4a9646557746a995c065090d09eb Mon Sep 17 00:00:00 2001
From: Paul Kirth <pk1574 at gmail.com>
Date: Fri, 5 Jun 2026 22:26:47 -0700
Subject: [PATCH] [clang-doc] Clean up implementation with better casting

Having access to RTTI style casting lets us use slightly nicer
structures to clean up the overly complicated dispatch logic in merging
and other places.
---
 .../clang-doc/Representation.cpp              | 70 +++++--------------
 1 file changed, 19 insertions(+), 51 deletions(-)

diff --git a/clang-tools-extra/clang-doc/Representation.cpp b/clang-tools-extra/clang-doc/Representation.cpp
index 9c13f6bfa566d..414b5a2377bcf 100644
--- a/clang-tools-extra/clang-doc/Representation.cpp
+++ b/clang-tools-extra/clang-doc/Representation.cpp
@@ -180,70 +180,38 @@ void mergeUnkeyed<CommentInfo>(DocList<CommentInfo> &Target,
   }
 }
 
+template <typename T>
+static llvm::Error mergeTypedInfo(Info *&Reduced, Info *NewInfo,
+                                  llvm::BumpPtrAllocator &Arena) {
+  if (!Reduced)
+    Reduced = allocatePtr<T>(Arena, NewInfo->USR);
+  cast<T>(Reduced)->merge(std::move(*cast<T>(NewInfo)));
+  return llvm::Error::success();
+}
+
 llvm::Error mergeSingleInfo(doc::Info *&Reduced, doc::Info *NewInfo,
                             llvm::BumpPtrAllocator &Arena) {
-  if (!Reduced) {
-    switch (NewInfo->IT) {
-    case InfoType::IT_namespace:
-      Reduced = allocatePtr<NamespaceInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_record:
-      Reduced = allocatePtr<RecordInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_enum:
-      Reduced = allocatePtr<EnumInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_function:
-      Reduced = allocatePtr<FunctionInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_typedef:
-      Reduced = allocatePtr<TypedefInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_concept:
-      Reduced = allocatePtr<ConceptInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_variable:
-      Reduced = allocatePtr<VarInfo>(Arena, NewInfo->USR);
-      break;
-    case InfoType::IT_friend:
-      Reduced = allocatePtr<FriendInfo>(Arena, NewInfo->USR);
-      break;
-    default:
-      return llvm::createStringError(llvm::inconvertibleErrorCode(),
-                                     "unknown info type");
-    }
-  }
-
-  if (Reduced->IT != NewInfo->IT)
+  if (Reduced && Reduced->IT != NewInfo->IT)
     return llvm::createStringError(llvm::inconvertibleErrorCode(),
                                    "info types mismatch");
 
-  switch (Reduced->IT) {
+  switch (NewInfo->IT) {
   case InfoType::IT_namespace:
-    cast<NamespaceInfo>(Reduced)->merge(
-        std::move(*cast<NamespaceInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<NamespaceInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_record:
-    cast<RecordInfo>(Reduced)->merge(std::move(*cast<RecordInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<RecordInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_enum:
-    cast<EnumInfo>(Reduced)->merge(std::move(*cast<EnumInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<EnumInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_function:
-    cast<FunctionInfo>(Reduced)->merge(std::move(*cast<FunctionInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<FunctionInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_typedef:
-    cast<TypedefInfo>(Reduced)->merge(std::move(*cast<TypedefInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<TypedefInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_concept:
-    cast<ConceptInfo>(Reduced)->merge(std::move(*cast<ConceptInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<ConceptInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_variable:
-    cast<VarInfo>(Reduced)->merge(std::move(*cast<VarInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<VarInfo>(Reduced, NewInfo, Arena);
   case InfoType::IT_friend:
-    cast<FriendInfo>(Reduced)->merge(std::move(*cast<FriendInfo>(NewInfo)));
-    break;
+    return mergeTypedInfo<FriendInfo>(Reduced, NewInfo, Arena);
   default:
     return llvm::createStringError(llvm::inconvertibleErrorCode(),
                                    "unknown info type");