syntax_data: {"ast_node_type":"other","tokens":[{"end":89,"kind":"keyword","start":0,"text":"real_source_base_dir(\"lib/rustlib/rustc-src/rust\","}]}
source_snippet:         real_source_base_dir("lib/rustlib/rustc-src/rust", "compiler/rustc/src/main.rs");
context_before:         // This is the location used by the `rustc-dev` `rustup` component.