Improve attribute range handling for attributed function types in selection

This fix clangd/clangd#2488

Author: quanzhuo

clang-tools-extra/clangd/Selection.cpp

@@ -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);
+          return;
+        }
+      }
     }
     claimRange(getSourceRange(N), Result);
   }

clang-tools-extra/clangd/unittests/SelectionTests.cpp

@@ -311,6 +311,15 @@ TEST(SelectionTest, CommonAncestor) {
       {"[[void foo^()]];", "FunctionProtoTypeLoc"},
       {"[[^void foo^()]];", "FunctionDecl"},
       {"[[void ^foo()]];", "FunctionDecl"},
+      // Tricky case: with function attributes, the AttributedTypeLoc's range
+      // includes the function name, but we want the name to be associated with
+      // the FunctionDecl.
+      {"struct X { [[void ^foo() [[clang::lifetimebound]]]]; };",
+       "FunctionDecl"},
+      {"struct X { [[void ^foo() const [[clang::lifetimebound]]]]; };",
+       "FunctionDecl"},
+      {"struct X { [[const int* ^Get() const [[clang::lifetimebound]]]]; };",
+       "FunctionDecl"},
       // Tricky case: two VarDecls share a specifier.
       {"[[int ^a]], b;", "VarDecl"},
       {"[[int a, ^b]];", "VarDecl"},