[clang] [clang-repl] fix CleanUpPTU by removing decl according to C implicitly FuncitonDecl. (PR #178648)

[Yanzuo Liu via cfe-commits]

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@@ -182,6 +183,30 @@ void IncrementalParser::CleanUpPTU(TranslationUnitDecl *MostRecentTU) {
     }
   }
 
+  auto *ECCD = S.getASTContext().getExternCContextDecl();
+  if (auto *Map = ECCD->getPrimaryContext()->getLookupPtr()) {
+    for (auto &&[Key, List] : *Map) {
+      DeclContextLookupResult R = List.getLookupResult();
+      std::vector<NamedDecl *> NamedDeclsToRemove;
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zwuis wrote:

Use `SmallVector`.

https://llvm.org/docs/CodingStandards.html#c-standard-library

https://github.com/llvm/llvm-project/pull/178648