Fixes #924 Add context to dated information

Author: igaray

src/SUMMARY.md

@@ -107,7 +107,6 @@
         - [Lowering to logic](./traits/lowering-to-logic.md)
         - [Goals and clauses](./traits/goals-and-clauses.md)
         - [Canonical queries](./traits/canonical-queries.md)
-        - [Lowering module in rustc](./traits/lowering-module.md)
 - [Type checking](./type-checking.md)
     - [Method Lookup](./method-lookup.md)
     - [Variance](./variance.md)

src/about-this-guide.md

@@ -30,10 +30,25 @@ There are six parts to this guide:
 [p5]: ./part-5-intro.md
 [app]: ./appendix/background.md
 
-The Guide itself is of course open-source as well, and the sources can
-be found at the [GitHub repository]. If you find any mistakes in the
-guide, please file an issue about it, or even better, open a PR
-with a correction!
+### Constant change
+
+Keep in mind that `rustc` is a real production-quality product, being worked upon continuously by a
+sizeable set of contributors.
+As such, it has its fair share of codebase churn and technical debt.
+In addition, many of the ideas discussed throughout this guide are idealized designs that are not
+fully realized yet.
+All this makes keeping this guide completely up to date on everything very hard!
+
+The Guide itself is of course open-source as well, and the sources can be found at the
+[GitHub repository].
+If you find any mistakes in the guide, please file an issue about it, or even better, open a PR with
+a correction!
+
+If you do contribute to the guide, please see the corresponding
+[subsection on writing documentation](contributing.md#writing-documentation).
+
+> “‘All conditioned things are impermanent’ — when one sees this with wisdom, one turns away from
+> suffering.” _The Dhammapada, verse 277_
 
 ## Other places to find information
 

src/backend/backend-agnostic.md

@@ -1,8 +1,7 @@
 # Backend Agnostic Codegen
 
-In the future, it would be nice to allow other codegen backends (e.g.
-[Cranelift]). To this end, `rustc_codegen_ssa` provides an
-abstract interface for all backends to implement.
+As of January 2021, `rustc_codegen_ssa` provides an abstract interface for all backends to
+implement, to allow other codegen backends (e.g. [Cranelift]).
 
 [Cranelift]: https://github.com/bytecodealliance/wasmtime/tree/HEAD/cranelift
 

src/borrow_check/region_inference/member_constraints.md

@@ -92,8 +92,9 @@ member constraints come in.
 ## Choices are always lifetime parameters
 
 At present, the "choice" regions from a member constraint are always
-lifetime parameters from the current function. This falls out from the
-placement of impl Trait, though in the future it may not be the case.
+lifetime parameters from the current function. As of January 2021,
+this falls out from the placement of impl Trait, though in the future
+it may not be the case.
 We take some advantage of this fact, as it simplifies the current
 code. In particular, we don't have to consider a case like `'0 member
 of ['1, 'static]`, in which the value of both `'0` and `'1` are being

src/contributing.md

@@ -407,6 +407,11 @@ repo][rdgrepo]. The issue tracker in that repo is also a great way to find
 things that need doing. There are issues for beginners and advanced compiler
 devs alike!
 
+When contributing text to the guide, please contextualize the information in some time period.
+E.g. instead of writing _"Currently, ..."_, or _"In the future, ..."_, consider writing
+_"As of January 2021, ..."_.
+
+
 [rdg]: https://rustc-dev-guide.rust-lang.org/
 [rdgrepo]: https://github.com/rust-lang/rustc-dev-guide
 

src/diagnostics/lintstore.md

@@ -15,9 +15,11 @@ Unfortunately, a lot of the documentation we have refers to both of these as jus
 
 First, we have the lint declarations themselves: this is where the name and default lint level and
 other metadata come from. These are normally defined by way of the [`declare_lint!`] macro, which
-boils down to a static with type `&rustc_session::lint::Lint`. We lint against direct declarations
-without the use of the macro today (though this may change in the future, as the macro is somewhat
-unwieldy to add new fields to, like all macros by example).
+boils down to a static with type `&rustc_session::lint::Lint`.
+
+As of January 2021, we lint against direct declarations without the use of the macro today
+(although this may change in the future, as the macro is somewhat unwieldy to add new fields to,
+like all macros by example).
 
 Lint declarations don't carry any "state" - they are merely global identifers and descriptions of
 lints. We assert at runtime that they are not registered twice (by lint name).

src/overview.md

@@ -15,7 +15,6 @@ So first, let's look at what the compiler does to your code. For now, we will
 avoid mentioning how the compiler implements these steps except as needed;
 we'll talk about that later.
 
-
 - The compile process begins when a user writes a Rust source program in text
   and invokes the `rustc` compiler on it. The work that the compiler needs to
   perform is defined by command-line options. For example, it is possible to
@@ -159,17 +158,6 @@ satisfy/optimize for. For example,
 So, as you read through the rest of the guide, keep these things in mind. They
 will often inform decisions that we make.
 
-### Constant change
-
-Keep in mind that `rustc` is a real production-quality product.
-As such, it has its fair share of codebase churn and technical debt. A lot of
-the designs discussed throughout this guide are idealized designs that are not
-fully realized yet. And things keep changing so that it is hard to keep this
-guide completely up to date on everything!
-
-The compiler definitely has rough edges, but because of its design it is able
-to keep up with the requirements above.
-
 ### Intermediate representations
 
 As with most compilers, `rustc` uses some intermediate representations (IRs) to

src/parallel-rustc.md

@@ -1,9 +1,10 @@
 # Parallel Compilation
 
 Most of the compiler is not parallel. This represents an opportunity for
-improving compiler performance. Much effort has been put into parallelizing
-`rustc`, but it is still pretty early days for this work. There is a lot of
-design and correctness work that needs to be done.
+improving compiler performance.
+
+As of January 2021, work on explicitly parallelizing the compiler has stalled.
+There is a lot of design and correctness work that needs to be done.
 
 One can try out the current parallel compiler work by enabling it in the
 `config.toml`.

src/profiling.md

@@ -90,5 +90,5 @@ The llvm-lines output is affected by several options.
 
 MIR optimizations have little impact. Compared to the default `RUSTFLAGS="-Z mir-opt-level=1"`,
 level 0 adds 0.3GB and level 2 removes 0.2GB.
-Inlining currently only happens in LLVM, but this might change in the future.
+As of January 2021, inlining currently only happens in LLVM but this might change in the future.
 

src/queries/profiling.md

@@ -86,8 +86,8 @@ The trace of the queries has a formal structure; see
 We style this formal structure as follows:
 
 - **Timed passes:** Green boxes, when present (via `-Z time-passes`), represent
-  _timed passes_ in the compiler. In future versions, these passes may be
-  replaced by queries, explained below.
+  _timed passes_ in the compiler. As of January 2021 these passes are not queries, but may be
+  replaced by queries in future versions.
 - **Labels:** Some green and red boxes are labeled with text. Where they are
   present, the labels give the following information:
   - The [query's _provider_](#queries), sans its _key_ and its _result_, which