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Improve comments on TyCtxt and GlobalCtxt.

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This commit is contained in:
Nicholas Nethercote 2023-02-10 10:26:24 +11:00
parent 789dd0b2a2
commit c625880a41
1 changed files with 12 additions and 0 deletions
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12
compiler/rustc_middle/src/ty/context.rs
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@ -478,6 +478,17 @@ impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
/// [rustc dev guide] for more details. /// [rustc dev guide] for more details.
/// ///
/// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/ty.html /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/ty.html
///
/// An implementation detail: `TyCtxt` is a wrapper type for [GlobalCtxt],
/// which is the struct that actually holds all the data. `TyCtxt` derefs to
/// `GlobalCtxt`, and in practice `TyCtxt` is passed around everywhere, and all
/// operations are done via `TyCtxt`. A `TyCtxt` is obtained for a `GlobalCtxt`
/// by calling `enter` with a closure `f`. That function creates both the
/// `TyCtxt`, and an `ImplicitCtxt` around it that is put into TLS. Within `f`:
/// - The `ImplicitCtxt` is available implicitly via TLS.
/// - The `TyCtxt` is available explicitly via the `tcx` parameter, and also
/// implicitly within the `ImplicitCtxt`. Explicit access is preferred when
/// possible.
#[derive(Copy, Clone)] #[derive(Copy, Clone)]
#[rustc_diagnostic_item = "TyCtxt"] #[rustc_diagnostic_item = "TyCtxt"]
#[rustc_pass_by_value] #[rustc_pass_by_value]
@ -493,6 +504,7 @@ impl<'tcx> Deref for TyCtxt<'tcx> {
} }
} }
/// See [TyCtxt] for details about this type.
pub struct GlobalCtxt<'tcx> { pub struct GlobalCtxt<'tcx> {
pub arena: &'tcx WorkerLocal<Arena<'tcx>>, pub arena: &'tcx WorkerLocal<Arena<'tcx>>,
pub hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>, pub hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>,