Change the constructor of salsa::Id to const fn
#440
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bors r+ makes sense! |
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440: Change the constructor of `salsa::Id` to const fn r=nikomatsakis a=Y-Nak This change is motivated to allow interned structs to have default const instances and prefill them in db initialization. A specific example is managing symbols as a salsa interned struct in a compiler implementation. By declaring keywords as `const` symbols, we can handle keywords without going through their internal representation as rustc does (ref: [rustc_span::symbol](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/symbol.rs)). Conceptually, it'd look like the one below. ```rust #[salsa::interned] pub struct Symbol { data: String, } const SELF_SYM: Symbol = Symbol(salsa::Id::from_u32(1)) ... /// This function is called in db initialization. fn prefill(db: &dyn HirDb) { Symbol::new(db, "self".to_string()); ... } ``` Co-authored-by: Yoshitomo Nakanishi <yurayura.rounin.3@gmail.com>
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Build failed:
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The build failure originated from the trybuild test failure. This is because of the change of the error message emitted from rustc. I fixed it in the latest commit. |
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bors r+ |
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Build succeeded: |
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This change is motivated to allow interned structs to have default const instances and prefill them in db initialization.
A specific example is managing symbols as a salsa interned struct in a compiler implementation. By declaring keywords as
constsymbols, we can handle keywords without going through their internal representation as rustc does (ref: rustc_span::symbol).Conceptually, it'd look like the one below.