Support type inference for fold, method and array

example: fold

let a = vec![1, 2, 3];

// the sum of all of the elements of a
let sum = a.iter().fold(0, |acc/*: {int} (should be)*/, &x| acc + x);

assert_eq!(sum, 6);

example: method

let a = vec!["1", "2", "4"];

// the sum of all of the elements of a
let as_strings = a.iter().map(ToString::to_string);
    //^ Map<Iter<&str>, ToString::to_string> (should be)

example: array

let a = ["1", "2", "4"];

// the sum of all of the elements of a
let iter = a.iter();
    //^ Iter<&str> (should be)

[vlad20012]

“array” issue was fixed by #1664 “method” will be fixed by #1767 “fold” seems to work now, but I don’t completely know what commit fixed it

[vlad20012]

@farodin91 Uh, now understand. Your example was too ambigous =) Yes, acc inference faild. Ok