Tuple error message unhelpful when more than 12 elements

[mdinger]

12 element tuple works:

fn main() {
    let tup = (1,2,3,4,5,6,7,8,9,10,11,12);
    println!("{}", tup.val0());
}

13 element tuple doesn't:

fn main() {
    let tup = (1,2,3,4,5,6,7,8,9,10,11,12,13);
    println!("{}", tup.val0());
}

The error message is not helpful. It should state that tuples don't support more than 12 elements:

<anon>:3:24: 3:30 error: type `(<generic integer #0>,<generic integer #1>,<generic integer #2>,<generic integer #3>,<generic integer #4>,<generic integer #5>,<generic integer #6>,<generic integer #7>,<generic integer #8>,<generic integer #9>,<generic integer #10>,<generic integer #11>,<generic integer #12>)` does not implement any method in scope named `val0`
<anon>:3     println!("{}", tup.val0());
                                ^~~~~~
<anon>:3:20: 3:30 error: cannot determine a type for this bounded type parameter: unconstrained type
<anon>:3     println!("{}", tup.val0());
                            ^~~~~~~~~~
note: in expansion of format_args!
<std macros>:2:23: 2:77 note: expansion site
<std macros>:1:1: 3:2 note: in expansion of println!
<anon>:3:5: 3:32 note: expansion site
playpen: application terminated with error code 101

[huonw]

Tuples do support more than 12 elements, it's just the traits providing methods like val0 in the standard library are only (manually) implemented for tuples upto 12 elements.

E.g. this works fine

fn main() {
    let t = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20);
    let (x, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _)  = t;
    println!("{}", x);
}

(That said those traits are a hack.)

[mdinger]

Thanks for your clarifying. I'll close because the premise was wrong.