Infinite loop with syn::parse_str::<syn::Expr>("q^0:");

[catenacyber]

You can reproduce this bug with default features by calling
syn::parse_str::<syn::Expr>("q^0:");

This bug does not happen with feature full as this case seems handled here https://github.com/dtolnay/syn/blob/master/src/expr.rs#L1355

A fix could be to remove the check for input.peek(Token![as]) at https://github.com/dtolnay/syn/blob/master/src/expr.rs#L1402
(but I am not sure if it breaks other things)

[dtolnay]

Thanks! I published a fix in 1.0.66.