[PATCH] D154328: [AST] Add API to iterate already loaded specializations

[Jonas Hahnfeld via Phabricator via cfe-commits]

Hahnfeld added a comment.

Right, it's not ideal to land APIs without usage in Clang itself... The context is, once again, ROOT and the Cling interpreter (where we are already using this API via downstream patches): When unloading a "transaction" (now `PartialTranslationUnit` in `clang-repl`) we need to "unload" all contained declarations, ie make the code generator forget that it had already emitted them. For templates, this is a bit tricky so we need to iterate specializations without triggering more deserialization. This will get important with D41416 <https://reviews.llvm.org/D41416> where we only load needed specializations.

When playing a bit earlier this week, I learned that the problem related to "unloading" of template specializations can be observed upstream in `clang-repl`:

  clang-repl> template <typename T> void f() {}
  clang-repl> f<int>();
  clang-repl> %undo
  clang-repl> template <> void f<int>() {}
  In file included from <<< inputs >>>:1:
  input_line_3:1:18: error: explicit specialization of 'f<int>' after instantiation
      1 | template <> void f<int>() {}
        |                  ^
  input_line_2:1:1: note: implicit instantiation first required here
      1 | f<int>();
        | ^
  error: Parsing failed.

Let me see if I can come up a fix for that in `clang-repl` that would then need this API. But for now, it's also fine for us if the patch stays pending in review, still better than completely disconnected local commits...


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D154328/new/

https://reviews.llvm.org/D154328