rust/tests/ui/const-generics/generic_const_exprs/abstract-const-as-cast-2.stderr
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

36 lines
1.4 KiB
Plaintext

error: unconstrained generic constant
--> $DIR/abstract-const-as-cast-2.rs:7:25
|
LL | struct Foo<const N: u8>([u8; N as usize])
| ^^^^^^^^^^^^^^^^
|
help: try adding a `where` bound
|
LL | Evaluatable<{N as u128}>:, [(); N as usize]:;
| +++++++++++++++++++
error: unconstrained generic constant
--> $DIR/abstract-const-as-cast-2.rs:13:26
|
LL | struct Foo2<const N: u8>(Evaluatable::<{N as u128}>) where Evaluatable<{N as usize as u128 }>:;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: try adding a `where` bound
|
LL | struct Foo2<const N: u8>(Evaluatable::<{N as u128}>) where Evaluatable<{N as usize as u128 }>:, [(); {N as u128} as usize]:;
| +++++++++++++++++++++++++++++
error: unconstrained generic constant
--> $DIR/abstract-const-as-cast-2.rs:17:25
|
LL | struct Bar<const N: u8>([u8; (N + 2) as usize]) where [(); (N + 1) as usize]:;
| ^^^^^^^^^^^^^^^^^^^^^^
|
help: try adding a `where` bound
|
LL | struct Bar<const N: u8>([u8; (N + 2) as usize]) where [(); (N + 1) as usize]:, [(); (N + 2) as usize]:;
| +++++++++++++++++++++++++
error: aborting due to 3 previous errors