6b24fdf811
```
error: unconstrained generic constant
--> $DIR/const-argument-if-length.rs:18:10
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LL | pad: [u8; is_zst::<T>()],
| ^^^^^^^^^^^^^^^^^^^
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help: try adding a `where` bound
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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
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6 | bb::<{!N}>();
| ^^^^
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs:3539:36
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help: try adding a `where` bound
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5 | fn b<const N: bool>() where [(); {!N} as usize]: {
| ++++++++++++++++++++++++++
```
Fix #122395.
14 lines
292 B
Rust
14 lines
292 B
Rust
//@ run-rustfix
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#![feature(generic_const_exprs, adt_const_params)]
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#![allow(incomplete_features, dead_code)]
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struct FieldElement<const N: &'static str> {
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n: [u64; num_limbs(N)],
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//~^ ERROR unconstrained generic constant
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}
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const fn num_limbs(_: &str) -> usize {
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0
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}
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fn main() {}
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