rust/tests/ui/const-generics/defaults/generic-expr-default.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

25 lines
953 B
Plaintext

error: unconstrained generic constant
--> $DIR/generic-expr-default.rs:5:54
|
LL | pub fn needs_evaluatable_bound<const N1: usize>() -> Foo<N1> {
| ^^^^^^^
|
help: try adding a `where` bound
|
LL | pub fn needs_evaluatable_bound<const N1: usize>() -> Foo<N1> where [(); { N + 1 }]: {
| ++++++++++++++++++++++
error: unconstrained generic constant
--> $DIR/generic-expr-default.rs:14:58
|
LL | fn needs_evaluatable_bound_alias<T, const N: usize>() -> FooAlias<N>
| ^^^^^^^^^^^
|
help: try adding a `where` bound
|
LL | fn needs_evaluatable_bound_alias<T, const N: usize>() -> FooAlias<N> where [(); { N + 1 }]:
| ++++++++++++++++++++++
error: aborting due to 2 previous errors