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