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Add a comment warning against using associated type defaults <3

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Maybe Waffle 2022-12-16 15:10:48 +00:00
parent 7e79c575e9
commit 452c745518
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8
compiler/rustc_middle/src/query/keys.rs
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@ -15,6 +15,14 @@ use rustc_span::{Span, DUMMY_SP};
/// The `Key` trait controls what types can legally be used as the key
/// for a query.
pub trait Key: Sized {
// N.B. Most of the keys down below have `type CacheSelector = DefaultCacheSelector<Self>;`,
// it would be reasonable to use associated type defaults, to remove the duplication...
//
// ...But r-a doesn't support them yet and using a default here causes r-a to not infer
// return types of queries which is very annoying. Thus, until r-a support associated
// type defaults, plese restrain from using them here <3
//
// r-a issue: <https://github.com/rust-lang/rust-analyzer/issues/13693>
type CacheSelector;
/// Given an instance of this key, what crate is it referring to?