[clang] [clang][ASTImporter] Only reorder fields of RecordDecls (PR #77079)

[Michael Buch via cfe-commits]

https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/77079

Prior to `e9536698720ec524cc8b72599363622bc1a31558` (https://reviews.llvm.org/D154764) we only re-ordered the fields of `RecordDecl`s. The change refactored this logic to make sure `FieldDecl`s are imported before other member decls. However, this change also widened the types of `DeclContext`s we consider for re-ordering from `RecordDecl` to anything that's a `DeclContext`. This seems to have been just a drive-by cleanup.

Internally we've seen numerous crashes in LLDB where we try to perform this re-ordering fields of `ObjCInterfaceDecl`s.

This patch restores old behaviour where we limit the re-ordering to just `RecordDecl`s.

>From 544e2b12695fa572b08abc8efdceeadd63ebbde5 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Fri, 5 Jan 2024 10:41:55 +0000
Subject: [PATCH] [clang][ASTImporter] Only reorder fields of RecordDecls

Prior to `e9536698720ec524cc8b72599363622bc1a31558`
(https://reviews.llvm.org/D154764) we only re-ordered
the fields of `RecordDecl`s. The change refactored this
logic to make sure `FieldDecl`s are imported before other
member decls. However, this change also widened the types
of `DeclContext`s we consider for re-ordering from `RecordDecl`
to anything that's a `DeclContext`. This seems to have been
just a drive-by cleanup.

Internally we've seen numerous crashes in LLDB where we try to
perform this re-ordering fields of `ObjCInterfaceDecl`s.

This patch restores old behaviour where we limit the re-ordering
to just `RecordDecl`s.
---
 clang/lib/AST/ASTImporter.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 9ffae72346f2af..f03ea6e09e8b7e 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -2034,10 +2034,14 @@ ASTNodeImporter::ImportDeclContext(DeclContext *FromDC, bool ForceImport) {
     return ToDCOrErr.takeError();
   }
 
+  const auto *FromRD = dyn_cast<RecordDecl>(FromDC);
+  if (!FromRD)
+    return ChildErrors;
+
   DeclContext *ToDC = *ToDCOrErr;
   // Remove all declarations, which may be in wrong order in the
   // lexical DeclContext and then add them in the proper order.
-  for (auto *D : FromDC->decls()) {
+  for (auto *D : FromRD->decls()) {
     if (!MightNeedReordering(D))
       continue;
 
@@ -2055,7 +2059,7 @@ ASTNodeImporter::ImportDeclContext(DeclContext *FromDC, bool ForceImport) {
   }
 
   // Import everything else.
-  for (auto *From : FromDC->decls()) {
+  for (auto *From : FromRD->decls()) {
     if (MightNeedReordering(From))
       continue;