Unable to find libstd under RUST_SRC_PATH. #1139

% racer complete std::io::B
Unable to find libstd under RUST_SRC_PATH. N.B. RUST_SRC_PATH variable needs to point to the src directory inside a rust checkout e.g. "/home/foouser/src/rust/src". Current value ""/nix/store/fjghknnd4x9zpgx6hxznaiw6c7y0jr2s-rust-1.47.0-2020-10-07-18bf6b4f0/lib/rustlib/src/rust/library/libstd""

I use nix Mozilla-rust-overlay stable

nixpkgs.latest.rustChannels.stable.rust.override {
extensions = [ #
# "lldb-preview"
"clippy-preview"
# "miri-preview"
"rls-preview"
# "rust-analyzer-preview"
"rustfmt-preview"
"llvm-tools-preview"
"rust-analysis"
"rust-std"
"rustc-dev"
# "rustc-docs"
"rust-src"
]

Thanks