[clang-tools-extra] Improve attribute range handling for attributed function types in sel… (PR #163926)

[Quan Zhuo via cfe-commits]

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@@ -958,6 +958,18 @@ class SelectionVisitor : public RecursiveASTVisitor<SelectionVisitor> {
         claimRange(SourceRange(FTL.getLParenLoc(), FTL.getEndLoc()), Result);
         return;
       }
+      if (auto ATL = TL->getAs<AttributedTypeLoc>()) {
+        // For attributed function types like `int foo() [[attr]]`, the
+        // AttributedTypeLoc's range includes the function name. We want to
+        // allow the function name to be associated with the FunctionDecl
+        // rather than the AttributedTypeLoc, so we only claim the attribute
+        // range itself.
+        if (ATL.getModifiedLoc().getAs<FunctionTypeLoc>()) {
+          // Only claim the attribute's source range, not the whole type.
+          claimRange(ATL.getLocalSourceRange(), Result);
----------------
quanzhuo wrote:

The `RecursiveASTVisitor` automatically traverses the inner type of `AttributedTypeLoc`. Looking at the RAV implementation in RecursiveASTVisitor.h:

```cpp
DEF_TRAVERSE_TYPELOC(AttributedType,
                     { TRY_TO(TraverseTypeLoc(TL.getModifiedLoc())); })
```

This means when we visit an `AttributedTypeLoc`, the RAV will automatically traverse its `ModifiedLoc` (the inner `FunctionTypeLoc`). 

So the flow is:
1. We encounter `AttributedTypeLoc` and only claim the attribute's source range
2. RAV automatically traverses the inner `FunctionTypeLoc` 
3. The existing special handling for `FunctionTypeLoc` (lines 957-959) claims the parameter list range

If we claim the function's parameter list in the `AttributedTypeLoc` handler as suggested, it would be claimed twice: once in the `AttributedTypeLoc` case and again when the inner `FunctionTypeLoc` is traversed.

https://github.com/llvm/llvm-project/pull/163926