[clang-tools-extra] [clang-reorder-fields] Prevent rewriting unsupported cases (PR #142149)

[Vladimir Vuksanovic via cfe-commits]

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@@ -50,6 +50,55 @@ static const RecordDecl *findDefinition(StringRef RecordName,
   return selectFirst<RecordDecl>("recordDecl", Results);
 }
 
+static bool isSafeToRewrite(const RecordDecl *Decl, const ASTContext &Context) {
+  // Don't attempt to rewrite if there is a declaration like 'int a, b;'.
+  SourceLocation LastTypeLoc;
+  for (const auto &Field : Decl->fields()) {
+    SourceLocation TypeLoc =
+        Field->getTypeSourceInfo()->getTypeLoc().getBeginLoc();
+    if (LastTypeLoc.isValid() && TypeLoc == LastTypeLoc)
+      return false;
+    LastTypeLoc = TypeLoc;
+  }
+
+  // Don't attempt to rewrite if a single macro expansion creates multiple
+  // fields.
+  SourceLocation LastMacroLoc;
+  for (const auto &Field : Decl->fields()) {
+    if (!Field->getLocation().isMacroID())
+      continue;
+    SourceLocation MacroLoc =
+        Context.getSourceManager().getExpansionLoc(Field->getLocation());
+    if (LastMacroLoc.isValid() && MacroLoc == LastMacroLoc)
+      return false;
+    LastMacroLoc = MacroLoc;
+  }
+
+  // Skip if there are preprocessor directives present.
+  const SourceManager &SM = Context.getSourceManager();
+  std::pair<FileID, unsigned> FileAndOffset =
+      SM.getDecomposedLoc(Decl->getSourceRange().getBegin());
+  unsigned EndOffset = SM.getFileOffset(Decl->getSourceRange().getEnd());
+  StringRef SrcBuffer = SM.getBufferData(FileAndOffset.first);
+  Lexer L(SM.getLocForStartOfFile(FileAndOffset.first), Context.getLangOpts(),
+          SrcBuffer.data(), SrcBuffer.data() + FileAndOffset.second,
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vvuksanovic wrote:

I agree. Changed the range and added a test.

https://github.com/llvm/llvm-project/pull/142149