[PATCH] D110810: [clang][ASTImporter] Simplify code of attribute import [NFC].

Fri Oct 1 04:41:14 PDT 2021

steakhal added inline comments.

================
Comment at: clang/lib/AST/ASTImporter.cpp:8530-8531

+  // Get the result of the previous import attempt (can be used only once).
+  llvm::Expected<Attr *> getResult() {
+    if (Err)
----------------
aaron.ballman wrote:
> steakhal wrote:
> > If it can be used only once, we should mark this function as an `r-value` function.
> > There is a similar macro already defined as `LLVM_LVALUE_FUNCTION`.
> > 
> > Later, when you would actually call this function, you need to `std::move()` the object, signifying that the original object gets destroyed in the process.
> > 
> > @aaron.ballman Do you think we need to define `LLVM_RVALUE_FUNCTION` or we can simply use the `&&` in the function declaration?
> > I've seen that you tried to substitute all `LLVM_LVALUE_FUNCTION` macros in the past. What's the status on this?
> The expected pattern is:
> ```
> #if LLVM_HAS_RVALUE_REFERENCE_THIS
>   void func() && {
>   }
> #endif
> ```
> https://github.com/llvm/llvm-project/blob/main/clang/include/clang/ASTMatchers/ASTMatchersInternal.h#L609 (and elsewhere). However, I note that there are some unprotected uses (such as https://github.com/llvm/llvm-project/blob/main/clang/lib/Tooling/Syntax/BuildTree.cpp#L437) and so it may be a sign that we're fine to remove `LLVM_HAS_RVALUE_REFERENCE_THIS` because all our supported compilers do the right thing?
You tried to eliminate that on Jan 22, 2020 with rGdfe9f130e07c929d21f8122272077495de531a38.
But according to git blame, the BuildTree.cpp#L437 was committed on Jul 9, 2019 with rG9b3f38f99085e2bbf9db01bb00d4c6d837f0fc00.
I'm confused.

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https://reviews.llvm.org/D110810