Do not hard error on broken constants in type aliases #82700
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rust-highfive
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lcnr
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Mar 2, 2021
| @@ -311,7 +311,19 @@ pub fn eval_to_allocation_raw_provider<'tcx>( | |||
| // <https://github.com/rust-lang/rust/issues/71800>. | |||
| let emit_as_lint = if let Some(def) = def.as_local() { | |||
| // (Associated) consts only emit a lint, since they might be unused. | |||
| matches!(tcx.def_kind(def.did.to_def_id()), DefKind::Const | DefKind::AssocConst) | |||
| matches!(tcx.def_kind(def.did.to_def_id()), DefKind::Const | DefKind::AssocConst) || { | |||
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afaict this also only emits this as a lint even if we are using the associated const which doesn't seem desirable to me
what's the result for the following with this change?
type Foo = [u8; 0 - 1];
fn foo() -> Foo {
todo!()
}and
struct Q<const N: usize>;
type Foo = Q<{0 - 1}>;
impl Default for Foo {
fn default() -> Self {
Q
}
}There was a problem hiding this comment.
Yes, these will become future incompat lints, too
|
Oh no, why does this error reporting logic just keep becoming more bespoke. :( What is the long-term plan for this? |
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crlf0710
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Interpreting the thumbs up and comment on https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/erroneous.20constants.20in.20type.20alias/near/229492342 as we don't need this and can just hard error |
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In #69741 @estebank was adding WF checks to type aliases. This will evaluate all constants in a type alias, which wasn't happening before, so that would be a breaking change. Thus I proactively excluded these constants from the hard error list, and we instead emit the future incompat lint. More context: #69741 (comment)
r? @lcnr
cc @rust-lang/wg-const-eval