rust/tests/ui/generic-const-items/evaluatable-bounds.fixed
Esteban Küber 6b24fdf811 Provide structured suggestion for unconstrained generic constant
```
error: unconstrained generic constant
  --> $DIR/const-argument-if-length.rs:18:10
   |
LL |     pad: [u8; is_zst::<T>()],
   |          ^^^^^^^^^^^^^^^^^^^
   |
help: try adding a `where` bound
   |
LL | pub struct AtLeastByte<T: ?Sized> where [(); is_zst::<T>()]: {
   |                                   ++++++++++++++++++++++++++
```

Detect when the constant expression isn't `usize` and suggest casting:

```
error: unconstrained generic constant
 --> f300.rs:6:10
  |
6 |     bb::<{!N}>();
  |          ^^^^
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs:3539:36
  |
help: try adding a `where` bound
  |
5 | fn b<const N: bool>() where [(); {!N} as usize]: {
  |                       ++++++++++++++++++++++++++
```

Fix #122395.
2024-03-21 00:03:59 +00:00

26 lines
621 B
Rust

// This is a regression test for issue #104400.
//@ run-rustfix
// Test that we can constrain generic const items that appear inside associated consts by
// adding a (makeshift) "evaluatable"-bound to the item, after applying the suggestion.
#![feature(generic_const_items, generic_const_exprs)]
#![allow(incomplete_features)]
trait Trait {
const LEN: usize;
const ARRAY: [i32; Self::LEN] where [(); Self::LEN]:; //~ ERROR unconstrained generic constant
}
impl Trait for () {
const LEN: usize = 2;
const ARRAY: [i32; Self::LEN] = [360, 720];
}
fn main() {
let [_, _] = <() as Trait>::ARRAY;
}