Parser for Rust source code is a major Rust crate for parsing Rust source code (token streams) into a syntax tree (AST) that procedural macros can inspect or transform. The primary target is macro authors: you can parse TokenStreams into syn::File, syn::Item, syn::Expr, syn::Type, etc. It offers rich data structures, fine-grained parsing, span tracking (for error reporting), traversal and mutation APIs (visit, fold, visit_mut), printing back to tokens, and strong feature-gating so you only compile what you need. ...