[clang-tools-extra] [include-cleaner] Handle symbols from system headers. (PR #66089)

[kadir çetinkaya via cfe-commits]

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@@ -188,6 +290,20 @@ llvm::SmallVector<Hinted<Header>> findHeaders(const SymbolLocation &Loc,
     OptionalFileEntryRef FE = SM.getFileEntryRefForID(FID);
     if (!FE)
       return {};
+
+    if (SrcMgr::isSystem(
+            SM.getSLocEntry(FID).getFile().getFileCharacteristic())) {
+      if (auto MappingHeader = SystemIncludeMap::get().mapHeader(FE->getName());
+          !MappingHeader.empty()) {
+        for (auto &Header : MappingHeader)
+          Results.emplace_back(Header, Hints::PublicHeader);
+        assert(!Results.empty());
+        Results.front().Hint |= Hints::PreferredHeader;
+        // FIXME: should we include the original header as well?
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kadircet wrote:

yes, i think we should treat these similar to IWYU private -> public mappings.

https://github.com/llvm/llvm-project/pull/66089