Cannot use `tiny_vec!` with one non-constant element

[TonalidadeHidrica]

The following code tries to create a TinyVec with a single element, but it fails at the tiny_vec!. (playground)

use tinyvec::{TinyVec, tiny_vec};

fn main() {
    let a = 1;
    let _: TinyVec<[u8; 4]> = tiny_vec![a];
}

   Compiling playground v0.0.1 (/playground)
error[E0435]: attempt to use a non-constant value in a constant
 --> src/main.rs:5:41
  |
5 |     let _: TinyVec<[u8; 4]> = tiny_vec![a];
  |                                         ^ non-constant value
  |
help: consider using `const` instead of `let`
  |
4 |     const a: /* Type */ = 1;
  |     ~~~~~  ++++++++++++

For more information about this error, try `rustc --explain E0435`.
error: could not compile `playground` (bin "playground") due to 1 previous error

This does not seem to happen for zero or two elements, or when the type is declared on its left (tiny_vec![ [u8; 4] => a ]).

[pr2502]

the problem appears to be with the pattern here https://github.com/Lokathor/tinyvec/blob/main/src/tinyvec.rs#L56-L61 getting a priority over the next branch. for a quick an dirty fix you can wrap a in braces to disambiguate it as an expression and not a type.

use tinyvec::{TinyVec, tiny_vec};

fn main() {
    let a = 1;
    let _: TinyVec<[u8; 4]> = tiny_vec![{a}];
}

[Lokathor]

We've had occasional problems with this macro before, and unfortunately I think the answer is that it just "is what it is" at this point. If we try to reorder the macro arms then it probably breaks someone.

We should probably document this on the macro at least, even if we can't fix it fully.