https://doc.rust-lang.org/reference
https://doc.rust-lang.org/nightly/reference/
https://github.com/rust-lang-nursery/reference

https://doc.rust-lang.org/stable/grammar.html

https://doc.rust-lang.org/reference/introduction.html
https://doc.rust-lang.org/reference/statements-and-expressions.html
https://doc.rust-lang.org/reference/statements.html
https://doc.rust-lang.org/reference/expressions.html
https://doc.rust-lang.org/reference/expressions/operator-expr.html