[PATCH] D75492: [modernize-use-using] Don't diagnose typedefs in `extern "C"` DeclContexts

[George Burgess IV via Phabricator via cfe-commits]

george.burgess.iv created this revision.
george.burgess.iv added a reviewer: aaron.ballman.

If code is shared between C and C++, converting a `typedef` to a `using` isn't possible. Being more conservative about emitting these lints in `extern "C"` blocks seems like a good compromise to me.


https://reviews.llvm.org/D75492

Files:
  clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
  clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
@@ -278,3 +278,7 @@
 // CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use 'using' instead of 'typedef'
 // CHECK-FIXES: using EnumT2_CheckTypedefImpactFromAnotherFile = enum { ea2, eb2 };
 
+extern "C" {
+typedef int Type;
+// No messages expected, since this code may be shared verbatim with C.
+}
Index: clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
+++ clang-tools-extra/clang-tidy/modernize/UseUsingCheck.cpp
@@ -48,6 +48,9 @@
   if (StartLoc.isMacroID() && IgnoreMacros)
     return;
 
+  if (MatchedDecl->getDeclContext()->isExternCContext())
+    return;
+
   static const char *UseUsingWarning = "use 'using' instead of 'typedef'";
 
   // Warn at StartLoc but do not fix if there is macro or array.


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