6b24fdf811
```
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.
55 lines
1.9 KiB
Plaintext
55 lines
1.9 KiB
Plaintext
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>()]: {
|
|
| ++++++++++++++++++++++++++
|
|
|
|
error[E0277]: the size for values of type `T` cannot be known at compilation time
|
|
--> $DIR/const-argument-if-length.rs:16:12
|
|
|
|
|
LL | pub struct AtLeastByte<T: ?Sized> {
|
|
| - this type parameter needs to be `Sized`
|
|
LL | value: T,
|
|
| ^ doesn't have a size known at compile-time
|
|
|
|
|
= note: only the last field of a struct may have a dynamically sized type
|
|
= help: change the field's type to have a statically known size
|
|
help: consider removing the `?Sized` bound to make the type parameter `Sized`
|
|
|
|
|
LL - pub struct AtLeastByte<T: ?Sized> {
|
|
LL + pub struct AtLeastByte<T> {
|
|
|
|
|
help: borrowed types always have a statically known size
|
|
|
|
|
LL | value: &T,
|
|
| +
|
|
help: the `Box` type always has a statically known size and allocates its contents in the heap
|
|
|
|
|
LL | value: Box<T>,
|
|
| ++++ +
|
|
|
|
error[E0277]: the size for values of type `T` cannot be known at compilation time
|
|
--> $DIR/const-argument-if-length.rs:7:28
|
|
|
|
|
LL | pub const fn is_zst<T: ?Sized>() -> usize {
|
|
| - this type parameter needs to be `Sized`
|
|
LL | if std::mem::size_of::<T>() == 0 {
|
|
| ^ doesn't have a size known at compile-time
|
|
|
|
|
note: required by an implicit `Sized` bound in `std::mem::size_of`
|
|
--> $SRC_DIR/core/src/mem/mod.rs:LL:COL
|
|
help: consider removing the `?Sized` bound to make the type parameter `Sized`
|
|
|
|
|
LL - pub const fn is_zst<T: ?Sized>() -> usize {
|
|
LL + pub const fn is_zst<T>() -> usize {
|
|
|
|
|
|
|
error: aborting due to 3 previous errors
|
|
|
|
For more information about this error, try `rustc --explain E0277`.
|