Macro assert_tokens_eq 

macro_rules! assert_tokens_eq {
    ($a:expr, $b:expr$(, $($arg:tt)*)?) => { ... };
    ($a:expr, str $b:literal$(, $($arg:tt)*)?) => { ... };
}

Helper macro that asserts that two entities implementing ToTokens result in the same TokenStream. Used in tests to ensure that the output of parsing is as expected. This macro allows two forms:

• The first form takes two expressions, both expressions are converted into canonical strings with .tokens_to_string() to be compared.
• The second form takes a string literal prefixed with str as second parameter. This string literal is then taken literally for the comparison.

The later form is used for testing Joint punctuation and whitespace placement.