tree-sitter-rust

Rust grammar for tree-sitter

Features

• Speed - When initially parsing a file, tree-sitter-rust takes around twice as long as Rustc's hand-coded parser.

  $ wc -l examples/ast.rs
    2157 examples/ast.rs
  
  $ rustc -Z ast-json-noexpand -Z time-passes examples/ast.rs | head -n1
    time: 0.007	parsing # (7 ms)
  
  $ tree-sitter parse examples/ast.rs --quiet --time
    examples/ast.rs	16 ms

  But if you edit the file after parsing it, this parser can generally update the previous existing syntax tree to reflect your edit in less than a millisecond, thanks to Tree-sitter's incremental parsing system.

• Token tree parsing - The content of a macro definition or macro invocation is treated by the Rust parser as a token tree - a sequence of tokens with no structure except for the matching of the delimiters (), [], and {}. In practice though, many arguments to macros are valid rust expressions or declarations. For code analysis tasks like syntax highlighting, it's useful to understand the structure of this code.

  Tree-sitter-rust attempts to parse the contents of token trees as expressions and declarations, falling back to unstructured token sequences if it can't find a structured interpretation. Because of Tree-sitter's efficient ambiguity handling, this additional parsing adds only a small performance cost.

References

• The Rust Grammar Reference - The grammar reference provides chapters that formally define the language grammar.
• The Rust Reference - While Rust does not have a specification, the reference tries to describe its working in detail. It tends to be out of date.
• Syntax Index - This appendix from The Book contains examples of all syntax in Rust cross-referenced with the section of The Book that describes it.