How to read the rust-lang source code smoothly?

when i wanna read the rust-lang core crate with vscode, the rust-analizer plugin report:
foundduplicate lang item unsafe_cell
the lang item is first defined in crate core. [which is the current project i read now]

1 first definition in core loaded from /Users/brettkk/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib/libcore-908209eee60fb642.rlib

2 second definition in the local crate (core)rustcE0152

of course, I know why dumplicated. one is that I clone the rust-lang crate and going to read the core library code; another is that i have installed the rust.....

but how to read the core libray code smoothly?

No guarantees, but this might help: