rust/tests/ui/structs/default-field-values/invalid-const.rs

#![feature(default_field_values, generic_const_exprs)]
#![allow(incomplete_features)]

pub struct Bat {
    pub bax: u8 = panic!("asdf"),
    //~^ ERROR evaluation of constant value failed
}

pub struct Baz<const C: u8> {
    pub bax: u8 = 130 + C, // ok
    pub bat: u8 = 130 + 130,
    //~^ ERROR evaluation of `Baz::<C>::bat::{constant#0}` failed
    pub bay: u8 = 1, // ok
}

fn main() {}
Introduce `default_field_values` feature Initial implementation of `#[feature(default_field_values]`, proposed in https://github.com/rust-lang/rfcs/pull/3681. Support default fields in enum struct variant Allow default values in an enum struct variant definition: ```rust pub enum Bar { Foo { bar: S = S, baz: i32 = 42 + 3, } } ``` Allow using `..` without a base on an enum struct variant ```rust Bar::Foo { .. } ``` `#[derive(Default)]` doesn't account for these as it is still gating `#[default]` only being allowed on unit variants. Support `#[derive(Default)]` on enum struct variants with all defaulted fields ```rust pub enum Bar { #[default] Foo { bar: S = S, baz: i32 = 42 + 3, } } ``` Check for missing fields in typeck instead of mir_build. Expand test with `const` param case (needs `generic_const_exprs` enabled). Properly instantiate MIR const The following works: ```rust struct S<A> { a: Vec<A> = Vec::new(), } S::<i32> { .. } ``` Add lint for default fields that will always fail const-eval We allow this to happen for API writers that might want to rely on users' getting a compile error when using the default field, different to the error that they would get when the field isn't default. We could change this to always error instead of being a lint, if we wanted. This will not catch errors for partially evaluated consts, like when the expression relies on a const parameter. Suggestions when encountering `Foo { .. }` without `#[feature(default_field_values)]`: - Suggest adding a base expression if there are missing fields. - Suggest enabling the feature if all the missing fields have optional values. - Suggest removing `..` if there are no missing fields. 2024-08-24 17:22:48 +00:00			`#![feature(default_field_values, generic_const_exprs)]`
			`#![allow(incomplete_features)]`

			`pub struct Bat {`
			`pub bax: u8 = panic!("asdf"),`
			`//~^ ERROR evaluation of constant value failed`
			`}`

			`pub struct Baz<const C: u8> {`
			`pub bax: u8 = 130 + C, // ok`
			`pub bat: u8 = 130 + 130,`
			//~^ ERROR evaluation of `Baz::<C>::bat::{constant#0}` failed
			`pub bay: u8 = 1, // ok`
			`}`

			`fn main() {}`