[iopq]

Here is a simpler syntax:

   fn accumulate tuples: &[(&'a Str, &Fn(i32) -> Bool)], i: i32 -> t
   where
        t: Monoid + From &'a Str + From String,

this is how Haskell with lifetimes and borrowing would look like (if arguments were not curried)

[Rusky]

This is arguably less readable, because it's missing some delimiters for your eyes to latch onto.

It's also not realistically parseable- the Haskell/Ocaml-like removal of <>s and ()s relies on application being left-associative, and if you read this under that rule you've changed the meaning (e.g. `From &'a Str`).

[olavk]

I like removing superfluous punctuation, but if parentheses are removed from method signatures than they should also be removed from invocations, which in turn comes with its own set of readability issues. I'm not a fan of the $ operator in Haskell, for example.