[clang] [clang-tools-extra] [clangd] Autocomplete fixes for methods (PR #165916)

[Hippolyte Melica via cfe-commits]

etyloppihacilem wrote:

Hi, thanks for your review, I added comments, removed the unused code block (which I manually tested) and changed a few names.

https://github.com/llvm/llvm-project/pull/165916