[clang-tools-extra] [clangd] Implement fold range for #pragma region (PR #168177)

[kadir çetinkaya via cfe-commits]

kadircet wrote:

hi, looks like this broke c++20 build bots, can you PTAL ? https://lab.llvm.org/buildbot/#/builders/108/builds/20160

https://github.com/llvm/llvm-project/pull/168177