rust/tests/ui/const-generics/issues/issue-84659.rs

//@ run-rustfix
#![allow(incomplete_features, dead_code, unused_braces)]
#![feature(generic_const_exprs)]

trait Bar<const N: usize> {}

trait Foo<'a> {
    const N: usize;
    type Baz: Bar<{ Self::N }>;
    //~^ ERROR: unconstrained generic constant
}

fn main() {}
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. 2024-03-20 19:03:59 -05:00			`//@ run-rustfix`
			`#![allow(incomplete_features, dead_code, unused_braces)]`
E-not-needs-test 2021-09-02 15:20:51 -05:00			`#![feature(generic_const_exprs)]`

			`trait Bar<const N: usize> {}`

			`trait Foo<'a> {`
			`const N: usize;`
			`type Baz: Bar<{ Self::N }>;`
			`//~^ ERROR: unconstrained generic constant`
			`}`

			`fn main() {}`