[clang] [clang-repl] Fix assertion failure in CleanUpPTU() (PR #85378)

[Stefan Gränitz via cfe-commits]

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@@ -375,16 +375,22 @@ void IncrementalParser::CleanUpPTU(PartialTranslationUnit &PTU) {
   TranslationUnitDecl *MostRecentTU = PTU.TUPart;
   TranslationUnitDecl *FirstTU = MostRecentTU->getFirstDecl();
   if (StoredDeclsMap *Map = FirstTU->getPrimaryContext()->getLookupPtr()) {
-    for (auto I = Map->begin(); I != Map->end(); ++I) {
-      StoredDeclsList &List = I->second;
+    for (auto &&[Key, List] : *Map) {
       DeclContextLookupResult R = List.getLookupResult();
+      std::vector<NamedDecl *> NamedDeclsToRemove;
+      bool RemoveAll = true;
       for (NamedDecl *D : R) {
-        if (D->getTranslationUnitDecl() == MostRecentTU) {
+        if (D->getTranslationUnitDecl() == MostRecentTU)
+          NamedDeclsToRemove.push_back(D);
+        else
+          RemoveAll = false;
+      }
+      if (LLVM_LIKELY(RemoveAll)) {
+        Map->erase(Key);
+      } else {
+        for (NamedDecl *D : NamedDeclsToRemove)
           List.remove(D);
-        }
       }
-      if (List.isNull())
-        Map->erase(I);
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weliveindetail wrote:

It happens above on `RemoveAll`. If we find that all `NamedDecl`s must be removed from `List`, we can just remove `List` from `Map` directly right? (Instead of removing all `NamedDeclsToRemove` from `List` first.)

https://github.com/llvm/llvm-project/pull/85378