syntax_data: {"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"real_source_base_dir(\"lib/rustlib/src/rust\","}]}
source_snippet:         real_source_base_dir("lib/rustlib/src/rust", "library/std/src/lib.rs");
context_before:         // This is the location used by the `rust-src` `rustup` component.