diff --git a/src/appendix/code-index.md b/src/appendix/code-index.md index 222c9b2db..52a7f42d6 100644 --- a/src/appendix/code-index.md +++ b/src/appendix/code-index.md @@ -29,7 +29,7 @@ Item | Kind | Short description | Chapter | `TraitDef` | struct | This struct contains a trait's definition with type information | [The `ty` modules] | [src/librustc/ty/trait_def.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/trait_def/struct.TraitDef.html) `TraitRef` | struct | The combination of a trait and its input types (e.g. `P0: Trait`) | [Trait Solving: Goals and Clauses], [Trait Solving: Lowering impls] | [src/librustc/ty/sty.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/struct.TraitRef.html) `Ty<'tcx>` | struct | This is the internal representation of a type used for type checking | [Type checking] | [src/librustc/ty/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/type.Ty.html) -`TyCtxt<'cx, 'tcx, 'tcx>` | struct | The "typing context". This is the central data structure in the compiler. It is the context that you use to perform all manner of queries | [The `ty` modules] | [src/librustc/ty/context.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/struct.TyCtxt.html) +`TyCtxt<'tcx>` | struct | The "typing context". This is the central data structure in the compiler. It is the context that you use to perform all manner of queries | [The `ty` modules] | [src/librustc/ty/context.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/struct.TyCtxt.html) [The HIR]: ../hir.html [Identifiers in the HIR]: ../hir.html#hir-id diff --git a/src/appendix/glossary.md b/src/appendix/glossary.md index a5d5bf56a..46c5c9f0f 100644 --- a/src/appendix/glossary.md +++ b/src/appendix/glossary.md @@ -25,7 +25,6 @@ early-bound lifetime | a lifetime region that is substituted at its definiti empty type | see "uninhabited type". Fat pointer | a two word value carrying the address of some value, along with some further information necessary to put the value to use. Rust includes two kinds of "fat pointers": references to slices, and trait objects. A reference to a slice carries the starting address of the slice and its length. A trait object carries a value's address and a pointer to the trait's implementation appropriate to that value. "Fat pointers" are also known as "wide pointers", and "double pointers". free variable | a "free variable" is one that is not bound within an expression or term; see [the background chapter for more](./background.html#free-vs-bound) -'gcx | the lifetime of the global arena ([see more](../ty.html)) generics | the set of generic type parameters defined on a type or item HIR | the High-level IR, created by lowering and desugaring the AST ([see more](../hir.html)) HirId | identifies a particular node in the HIR by combining a def-id with an "intra-definition offset". diff --git a/src/compiler-debugging.md b/src/compiler-debugging.md index 0126c2503..8f3a331aa 100644 --- a/src/compiler-debugging.md +++ b/src/compiler-debugging.md @@ -48,7 +48,7 @@ stack backtrace: If you want line numbers for the stack trace, you can enable `debug = true` in your config.toml and rebuild the compiler (`debuginfo-level = 1` will also add -line numbers, but `debug = true` gives full debuginfo). Then the backtrace will +line numbers, but `debug = true` gives full debuginfo). Then the backtrace will look like this: ```text @@ -129,11 +129,11 @@ note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. stack backtrace: (~~~ IRRELEVANT PART OF BACKTRACE REMOVED BY ME ~~~) - 7: rustc::traits::error_reporting::>::report_selection_error + 7: rustc::traits::error_reporting::> + ::report_selection_error at /home/user/rust/src/librustc/traits/error_reporting.rs:823 - 8: rustc::traits::error_reporting::>::report_fulfillment_errors + 8: rustc::traits::error_reporting::> + ::report_fulfillment_errors at /home/user/rust/src/librustc/traits/error_reporting.rs:160 at /home/user/rust/src/librustc/traits/error_reporting.rs:112 9: rustc_typeck::check::FnCtxt::select_obligations_where_possible diff --git a/src/conventions.md b/src/conventions.md index d9f462a05..a941ebff9 100644 --- a/src/conventions.md +++ b/src/conventions.md @@ -141,8 +141,7 @@ to the compiler. - `cx` tends to be short for "context" and is often used as a suffix. For example, `tcx` is a common name for the [Typing Context][tcx]. -- [`'tcx` and `'gcx`][tcx] are used as the lifetime names for the Typing - Context. +- [`'tcx`][tcx] is used as the lifetim names for the Typing Context. - Because `crate` is a keyword, if you need a variable to represent something crate-related, often the spelling is changed to `krate`. diff --git a/src/mir/visitor.md b/src/mir/visitor.md index ad00bc3f1..a5e8e9a0b 100644 --- a/src/mir/visitor.md +++ b/src/mir/visitor.md @@ -15,7 +15,7 @@ state you will need while processing MIR: ```rust,ignore struct MyVisitor<...> { - tcx: TyCtxt<'cx, 'tcx, 'tcx>, + tcx: TyCtxt<'tcx>, ... } ``` diff --git a/src/profiling/with_perf.md b/src/profiling/with_perf.md index 2634cc260..7582eece5 100644 --- a/src/profiling/with_perf.md +++ b/src/profiling/with_perf.md @@ -272,9 +272,9 @@ Tree : : | rustc_mir::borrow_check::nll::type_check::type_check_internal (13% total, 0% self) : : : | core::ops::function::FnOnce::call_once (5% total, 0% self) : : : : | rustc_mir::borrow_check::nll::type_check::liveness::generate (5% total, 3% self) -: : : | as rustc::mir::visit::Visitor<'tcx>>::visit_mir (3% total, 0% self) +: : : | as rustc::mir::visit::Visitor<'tcx>>::visit_mir (3% total, 0% self) : | rustc::mir::visit::Visitor::visit_mir (8% total, 6% self) -: | as rustc_mir::dataflow::DataflowResultsConsumer<'cx, 'tcx>>::visit_statement_entry (5% total, 0% self) +: | as rustc_mir::dataflow::DataflowResultsConsumer<'cx, 'tcx>>::visit_statement_entry (5% total, 0% self) : | rustc_mir::dataflow::do_dataflow (3% total, 0% self) ``` @@ -321,7 +321,7 @@ Tree | matched `{do_mir_borrowck}` (100% total, 0% self) : | rustc_mir::borrow_check::nll::compute_regions (47% total, 0% self) [...] : | rustc::mir::visit::Visitor::visit_mir (19% total, 15% self) [...] -: | as rustc_mir::dataflow::DataflowResultsConsumer<'cx, 'tcx>>::visit_statement_entry (13% total, 0% self) [...] +: | as rustc_mir::dataflow::DataflowResultsConsumer<'cx, 'tcx>>::visit_statement_entry (13% total, 0% self) [...] : | rustc_mir::dataflow::do_dataflow (8% total, 1% self) [...] ``` diff --git a/src/query.md b/src/query.md index 4d80187aa..4ab1d079e 100644 --- a/src/query.md +++ b/src/query.md @@ -82,17 +82,15 @@ on how that works). Providers always have the same signature: ```rust,ignore -fn provider<'cx, 'tcx>(tcx: TyCtxt<'cx, 'tcx, 'tcx>, - key: QUERY_KEY) - -> QUERY_RESULT -{ +fn provider<'tcx>( + tcx: TyCtxt<'tcx>, + key: QUERY_KEY, +) -> QUERY_RESULT { ... } ``` -Providers take two arguments: the `tcx` and the query key. Note also -that they take the *global* tcx (i.e. they use the `'tcx` lifetime -twice), rather than taking a tcx with some active inference context. +Providers take two arguments: the `tcx` and the query key. They return the result of the query. #### How providers are setup @@ -103,7 +101,7 @@ is basically a big list of function pointers: ```rust,ignore struct Providers { - type_of: for<'cx, 'tcx> fn(TyCtxt<'cx, 'tcx, 'tcx>, DefId) -> Ty<'tcx>, + type_of: for<'tcx> fn(TyCtxt<'tcx>, DefId) -> Ty<'tcx>, ... } ``` @@ -144,7 +142,7 @@ pub fn provide(providers: &mut Providers) { }; } -fn fubar<'cx, 'tcx>(tcx: TyCtxt<'cx, 'tcx>, key: DefId) -> Fubar<'tcx> { ... } +fn fubar<'tcx>(tcx: TyCtxt<'tcx>, key: DefId) -> Fubar<'tcx> { ... } ``` N.B. Most of the `rustc_*` crates only provide **local diff --git a/src/ty.md b/src/ty.md index d9979bc0b..72405d297 100644 --- a/src/ty.md +++ b/src/ty.md @@ -11,63 +11,19 @@ compiler. It is the context that you use to perform all manner of queries. The struct `TyCtxt` defines a reference to this shared context: ```rust,ignore -tcx: TyCtxt<'a, 'gcx, 'tcx> -// -- ---- ---- -// | | | -// | | innermost arena lifetime (if any) -// | "global arena" lifetime -// lifetime of this reference +tcx: TyCtxt<'tcx> +// ---- +// | +// arena lifetime ``` -As you can see, the `TyCtxt` type takes three lifetime parameters. -These lifetimes are perhaps the most complex thing to understand about -the tcx. During Rust compilation, we allocate most of our memory in +As you can see, the `TyCtxt` type takes a lifetime parameter. +During Rust compilation, we allocate most of our memory in **arenas**, which are basically pools of memory that get freed all at -once. When you see a reference with a lifetime like `'tcx` or `'gcx`, +once. When you see a reference with a lifetime like `'tcx`, you know that it refers to arena-allocated data (or data that lives as long as the arenas, anyhow). -We use two distinct levels of arenas. The outer level is the "global -arena". This arena lasts for the entire compilation: so anything you -allocate in there is only freed once compilation is basically over -(actually, when we shift to executing LLVM). - -To reduce peak memory usage, when we do type inference, we also use an -inner level of arena. These arenas get thrown away once type inference -is over. This is done because type inference generates a lot of -"throw-away" types that are not particularly interesting after type -inference completes, so keeping around those allocations would be -wasteful. - -Often, we wish to write code that explicitly asserts that it is not -taking place during inference. In that case, there is no "local" -arena, and all the types that you can access are allocated in the -global arena. To express this, the idea is to use the same lifetime -for the `'gcx` and `'tcx` parameters of `TyCtxt`. Just to be a touch -confusing, we tend to use the name `'tcx` in such contexts. Here is an -example: - -```rust,ignore -fn not_in_inference<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) { - // ---- ---- - // Using the same lifetime here asserts - // that the innermost arena accessible through - // this reference *is* the global arena. -} -``` - -In contrast, if we want to code that can be usable during type inference, then -you need to declare a distinct `'gcx` and `'tcx` lifetime parameter: - -```rust,ignore -fn maybe_in_inference<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, def_id: DefId) { - // ---- ---- - // Using different lifetimes here means that - // the innermost arena *may* be distinct - // from the global arena (but doesn't have to be). -} -``` - ### Allocating and working with types Rust types are represented using the `Ty<'tcx>` defined in the `ty` diff --git a/src/type-inference.md b/src/type-inference.md index d94c06379..d4734525f 100644 --- a/src/type-inference.md +++ b/src/type-inference.md @@ -50,9 +50,8 @@ function and disposed of after it returns. [ty-ch]: ty.html -Within the closure, `infcx` has the type `InferCtxt<'cx, 'gcx, 'tcx>` -for some fresh `'cx` and `'tcx` – the latter corresponds to the lifetime of -this temporary arena, and the `'cx` is the lifetime of the `InferCtxt` itself. +Within the closure, `infcx` has the type `InferCtxt<'cx, 'tcx>` for some +fresh `'cx`, while `'tcx` is the same as outside the inference context. (Again, see the [`ty` chapter][ty-ch] for more details on this setup.) The `tcx.infer_ctxt` method actually returns a builder, which means