reorg docs

2 files changed, 263 insertions, 268 deletions

diff --git a/docs/dev/README.md b/docs/dev/README.md
index 2896d333e..18c53d5c0 100644
--- a/docs/dev/README.md
+++ b/docs/dev/README.md
@@ -50,277 +50,85 @@ We use bors-ng to enforce the [not rocket science](https://graydon2.dreamwidth.o
 
 You can run `cargo xtask install-pre-commit-hook` to install git-hook to run rustfmt on commit.
 
-# Code organization
-
-All Rust code lives in the `crates` top-level directory, and is organized as a
-single Cargo workspace. The `editors` top-level directory contains code for
-integrating with editors. Currently, it contains the plugin for VS Code (in
-TypeScript). The `docs` top-level directory contains both developer and user
-documentation.
-
-We have some automation infra in Rust in the `xtask` package. It contains
-stuff like formatting checking, code generation and powers `cargo xtask install`.
-The latter syntax is achieved with the help of cargo aliases (see `.cargo`
-directory).
-
 # Launching rust-analyzer
 
-Debugging the language server can be tricky: LSP is rather chatty, so driving it
-from the command line is not really feasible, driving it via VS Code requires
-interacting with two processes.
+Debugging the language server can be tricky.
+LSP is rather chatty, so driving it from the command line is not really feasible, driving it via VS Code requires interacting with two processes.
 
-For this reason, the best way to see how rust-analyzer works is to find a
-relevant test and execute it (VS Code includes an action for running a single
-test).
+For this reason, the best way to see how rust-analyzer works is to find a relevant test and execute it.
+VS Code & Emacs include an action for running a single test.
 
-However, launching a VS Code instance with a locally built language server is
-possible. There's **"Run Extension (Debug Build)"** launch configuration for this.
+Launching a VS Code instance with a locally built language server is also possible.
+There's **"Run Extension (Debug Build)"** launch configuration for this in VS Code.
 
-In general, I use one of the following workflows for fixing bugs and
-implementing features.
+In general, I use one of the following workflows for fixing bugs and implementing features:
 
-If the problem concerns only internal parts of rust-analyzer (i.e. I don't need
-to touch the `rust-analyzer` crate or TypeScript code), there is a unit-test for it.
-So, I use **Rust Analyzer: Run** action in VS Code to run this single test, and
-then just do printf-driven development/debugging. As a sanity check after I'm
-done, I use `cargo xtask install --server` and **Reload Window** action in VS
-Code to sanity check that the thing works as I expect.
+If the problem concerns only internal parts of rust-analyzer (i.e. I don't need to touch the `rust-analyzer` crate or TypeScript code), there is a unit-test for it.
+So, I use **Rust Analyzer: Run** action in VS Code to run this single test, and then just do printf-driven development/debugging.
+As a sanity check after I'm done, I use `cargo xtask install --server` and **Reload Window** action in VS Code to verify that the thing works as I expect.
 
-If the problem concerns only the VS Code extension, I use **Run Installed Extension**
-launch configuration from `launch.json`. Notably, this uses the usual
-`rust-analyzer` binary from `PATH`. For this, it is important to have the following
-in your `settings.json` file:
+If the problem concerns only the VS Code extension, I use **Run Installed Extension** launch configuration from `launch.json`.
+Notably, this uses the usual `rust-analyzer` binary from `PATH`.
+For this, it is important to have the following in your `settings.json` file:
 ```json
 {
     "rust-analyzer.serverPath": "rust-analyzer"
 }
 ```
-After I am done with the fix, I use `cargo
-xtask install --client-code` to try the new extension for real.
-
-If I need to fix something in the `rust-analyzer` crate, I feel sad because it's
-on the boundary between the two processes, and working there is slow. I usually
-just `cargo xtask install --server` and poke changes from my live environment.
-Note that this uses `--release`, which is usually faster overall, because
-loading stdlib into debug version of rust-analyzer takes a lot of time. To speed
-things up, sometimes I open a temporary hello-world project which has
-`"rust-analyzer.withSysroot": false` in `.code/settings.json`. This flag causes
-rust-analyzer to skip loading the sysroot, which greatly reduces the amount of
-things rust-analyzer needs to do, and makes printf's more useful. Note that you
-should only use the `eprint!` family of macros for debugging: stdout is used for LSP
-communication, and `print!` would break it.
-
-If I need to fix something simultaneously in the server and in the client, I
-feel even more sad. I don't have a specific workflow for this case.
-
-Additionally, I use `cargo run --release -p rust-analyzer -- analysis-stats
-path/to/some/rust/crate` to run a batch analysis. This is primarily useful for
-performance optimizations, or for bug minimization.
-
-# Code Style & Review Process
-
-Our approach to "clean code" is two-fold:
-
-* We generally don't block PRs on style changes.
-* At the same time, all code in rust-analyzer is constantly refactored.
-
-It is explicitly OK for a reviewer to flag only some nits in the PR, and then send a follow-up cleanup PR for things which are easier to explain by example, cc-ing the original author.
-Sending small cleanup PRs (like renaming a single local variable) is encouraged.
-
-## Scale of Changes
-
-Everyone knows that it's better to send small & focused pull requests.
-The problem is, sometimes you *have* to, eg, rewrite the whole compiler, and that just doesn't fit into a set of isolated PRs.
-
-The main things to keep an eye on are the boundaries between various components.
-There are three kinds of changes:
-
-1. Internals of a single component are changed.
-   Specifically, you don't change any `pub` items.
-   A good example here would be an addition of a new assist.
-
-2. API of a component is expanded.
-   Specifically, you add a new `pub` function which wasn't there before.
-   A good example here would be expansion of assist API, for example, to implement lazy assists or assists groups.
-
-3. A new dependency between components is introduced.
-   Specifically, you add a `pub use` reexport from another crate or you add a new line to the `[dependencies]` section of `Cargo.toml`.
-   A good example here would be adding reference search capability to the assists crates.
-
-For the first group, the change is generally merged as long as:
-
-* it works for the happy case,
-* it has tests,
-* it doesn't panic for the unhappy case.
-
-For the second group, the change would be subjected to quite a bit of scrutiny and iteration.
-The new API needs to be right (or at least easy to change later).
-The actual implementation doesn't matter that much.
-It's very important to minimize the amount of changed lines of code for changes of the second kind.
-Often, you start doing a change of the first kind, only to realise that you need to elevate to a change of the second kind.
-In this case, we'll probably ask you to split API changes into a separate PR.
-
-Changes of the third group should be pretty rare, so we don't specify any specific process for them.
-That said, adding an innocent-looking `pub use` is a very simple way to break encapsulation, keep an eye on it!
-
-Note: if you enjoyed this abstract hand-waving about boundaries, you might appreciate
-https://www.tedinski.com/2018/02/06/system-boundaries.html
-
-## Crates.io Dependencies
-
-We try to be very conservative with usage of crates.io dependencies.
-Don't use small "helper" crates (exception: `itertools` is allowed).
-If there's some general reusable bit of code you need, consider adding it to the `stdx` crate.
-
-## Minimal Tests
-
-Most tests in rust-analyzer start with a snippet of Rust code.
-This snippets should be minimal -- if you copy-paste a snippet of real code into the tests, make sure to remove everything which could be removed.
-There are many benefits to this:
-
-* less to read or to scroll past
-* easier to understand what exactly is tested
-* less stuff printed during printf-debugging
-* less time to run test
-
-It also makes sense to format snippets more compactly (for example, by placing enum defitions like `enum E { Foo, Bar }` on a single line),
-as long as they are still readable.
-
-## Order of Imports
-
-We separate import groups with blank lines
+After I am done with the fix, I use `cargo xtask install --client-code` to try the new extension for real.
 
-```rust
-mod x;
-mod y;
+If I need to fix something in the `rust-analyzer` crate, I feel sad because it's on the boundary between the two processes, and working there is slow.
+I usually just `cargo xtask install --server` and poke changes from my live environment.
+Note that this uses `--release`, which is usually faster overall, because loading stdlib into debug version of rust-analyzer takes a lot of time.
+To speed things up, sometimes I open a temporary hello-world project which has `"rust-analyzer.withSysroot": false` in `.code/settings.json`.
+This flag causes rust-analyzer to skip loading the sysroot, which greatly reduces the amount of things rust-analyzer needs to do, and makes printf's more useful.
+Note that you should only use the `eprint!` family of macros for debugging: stdout is used for LSP communication, and `print!` would break it.
 
-use std::{ ... }
-
-use crate_foo::{ ... }
-use crate_bar::{ ... }
-
-use crate::{}
-
-use super::{} // but prefer `use crate::`
-```
-
-## Import Style
-
-Items from `hir` and `ast` should be used qualified:
-
-```rust
-// Good
-use ra_syntax::ast;
-
-fn frobnicate(func: hir::Function, strukt: ast::StructDef) {}
-
-// Not as good
-use hir::Function;
-use ra_syntax::ast::StructDef;
-
-fn frobnicate(func: Function, strukt: StructDef) {}
-```
-
-Avoid local `use MyEnum::*` imports.
-
-Prefer `use crate::foo::bar` to `use super::bar`.
-
-## Order of Items
-
-Optimize for the reader who sees the file for the first time, and wants to get the general idea about what's going on.
-People read things from top to bottom, so place most important things first.
-
-Specifically, if all items except one are private, always put the non-private item on top.
-
-Put `struct`s and `enum`s first, functions and impls last.
-
-Do
-
-```rust
-// Good
-struct Foo {
-    bars: Vec<Bar>
-}
-
-struct Bar;
-```
-
-rather than
-
-```rust
-// Not as good
-struct Bar;
-
-struct Foo {
-    bars: Vec<Bar>
-}
-```
+If I need to fix something simultaneously in the server and in the client, I feel even more sad.
+I don't have a specific workflow for this case.
 
-## Variable Naming
+Additionally, I use `cargo run --release -p rust-analyzer -- analysis-stats path/to/some/rust/crate` to run a batch analysis.
+This is primarily useful for performance optimizations, or for bug minimization.
 
-We generally use boring and long names for local variables ([yay code completion](https://github.com/rust-analyzer/rust-analyzer/pull/4162#discussion_r417130973)).
-The default name is a lowercased name of the type: `global_state: GlobalState`.
-Avoid ad-hoc acronyms and contractions, but use the ones that exist consistently (`db`, `ctx`, `acc`).
-The default name for "result of the function" local variable is `res`.
-
-## Collection types
+## Parser Tests
 
-We prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`.
-They use a hasher that's slightly faster and using them consistently will reduce code size by some small amount.
+Tests for the parser (`ra_parser`) live in the `ra_syntax` crate (see `test_data` directory).
+There are two kinds of tests:
 
-## Preconditions
+* Manually written test cases in `parser/ok` and `parser/err`
+* "Inline" tests in `parser/inline` (these are generated) from comments in `ra_parser` crate.
 
-Function preconditions should generally be expressed in types and provided by the caller (rather than checked by callee):
+The purpose of inline tests is not to achieve full coverage by test cases, but to explain to the reader of the code what each particular `if` and `match` is responsible for.
+If you are tempted to add a large inline test, it might be a good idea to leave only the simplest example in place, and move the test to a manual `parser/ok` test.
 
-```rust
-// Good
-fn frbonicate(walrus: Walrus) {
-    ...
-}
+To update test data, run with `UPDATE_EXPECT` variable:
 
-// Not as good
-fn frobnicate(walrus: Option<Walrus>) {
-    let walrus = match walrus {
-        Some(it) => it,
-        None => return,
-    };
-    ...
-}
+```bash
+env UPDATE_EXPECT=1 cargo qt
 ```
 
-## Premature Pessimization
-
-While we don't specifically optimize code yet, avoid writing code which is slower than it needs to be.
-Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly.
+After adding a new inline test you need to run `cargo xtest codegen` and also update the test data as described above.
 
-```rust
-// Good
-use itertools::Itertools;
+## TypeScript Tests
 
-let (first_word, second_word) = match text.split_ascii_whitespace().collect_tuple() {
-    Some(it) => it,
-    None => return,
-}
+If you change files under `editors/code` and would like to run the tests and linter, install npm and run:
 
-// Not as good
-let words = text.split_ascii_whitespace().collect::<Vec<_>>();
-if words.len() != 2 {
-    return
-}
+```bash
+cd editors/code
+npm ci
+npm run lint
 ```
 
-## Documentation
-
-For `.md` and `.adoc` files, prefer a sentence-per-line format, don't wrap lines.
-If the line is too long, you want to split the sentence in two :-)
-
-## Commit Style
+# Code organization
 
-We don't have specific rules around git history hygiene.
-Maintaining clean git history is encouraged, but not enforced.
-We use rebase workflow, it's OK to rewrite history during PR review process.
+All Rust code lives in the `crates` top-level directory, and is organized as a single Cargo workspace.
+The `editors` top-level directory contains code for integrating with editors.
+Currently, it contains the plugin for VS Code (in TypeScript).
+The `docs` top-level directory contains both developer and user documentation.
 
-Avoid @mentioning people in commit messages and pull request descriptions (they are added to commit message by bors), as such messages create a lot of duplicate notification traffic during rebases.
+We have some automation infra in Rust in the `xtask` package.
+It contains stuff like formatting checking, code generation and powers `cargo xtask install`.
+The latter syntax is achieved with the help of cargo aliases (see `.cargo` directory).
 
 # Architecture Invariants
 
@@ -355,35 +163,11 @@ The main IDE crate (`ra_ide`) uses "Plain Old Data" for the API.
 Rather than talking in definitions and references, it talks in Strings and textual offsets.
 In general, API is centered around UI concerns -- the result of the call is what the user sees in the editor, and not what the compiler sees underneath.
 The results are 100% Rust specific though.
+Shout outs to LSP developers for popularizing the idea that "UI" is a good place to draw a boundary at.
 
-## Parser Tests
-
-Tests for the parser (`ra_parser`) live in the `ra_syntax` crate (see `test_data` directory).
-There are two kinds of tests:
-
-* Manually written test cases in `parser/ok` and `parser/err`
-* "Inline" tests in `parser/inline` (these are generated) from comments in `ra_parser` crate.
-
-The purpose of inline tests is not to achieve full coverage by test cases, but to explain to the reader of the code what each particular `if` and `match` is responsible for.
-If you are tempted to add a large inline test, it might be a good idea to leave only the simplest example in place, and move the test to a manual `parser/ok` test.
-
-To update test data, run with `UPDATE_EXPECT` variable:
-
-```bash
-env UPDATE_EXPECT=1 cargo qt
-```
-
-After adding a new inline test you need to run `cargo xtest codegen` and also update the test data as described above.
-
-## TypeScript Tests
-
-If you change files under `editors/code` and would like to run the tests and linter, install npm and run:
+# Code Style & Review Process
 
-```bash
-cd editors/code
-npm ci
-npm run lint
-```
+Do see [./style.md](./style.md).
 
 # Logging
 
diff --git a/docs/dev/style.md b/docs/dev/style.md
new file mode 100644
index 000000000..0a85b4a55
--- /dev/null
+++ b/docs/dev/style.md
@@ -0,0 +1,211 @@
+Our approach to "clean code" is two-fold:
+
+* We generally don't block PRs on style changes.
+* At the same time, all code in rust-analyzer is constantly refactored.
+
+It is explicitly OK for a reviewer to flag only some nits in the PR, and then send a follow-up cleanup PR for things which are easier to explain by example, cc-ing the original author.
+Sending small cleanup PRs (like renaming a single local variable) is encouraged.
+
+# Scale of Changes
+
+Everyone knows that it's better to send small & focused pull requests.
+The problem is, sometimes you *have* to, eg, rewrite the whole compiler, and that just doesn't fit into a set of isolated PRs.
+
+The main things to keep an eye on are the boundaries between various components.
+There are three kinds of changes:
+
+1. Internals of a single component are changed.
+   Specifically, you don't change any `pub` items.
+   A good example here would be an addition of a new assist.
+
+2. API of a component is expanded.
+   Specifically, you add a new `pub` function which wasn't there before.
+   A good example here would be expansion of assist API, for example, to implement lazy assists or assists groups.
+
+3. A new dependency between components is introduced.
+   Specifically, you add a `pub use` reexport from another crate or you add a new line to the `[dependencies]` section of `Cargo.toml`.
+   A good example here would be adding reference search capability to the assists crates.
+
+For the first group, the change is generally merged as long as:
+
+* it works for the happy case,
+* it has tests,
+* it doesn't panic for the unhappy case.
+
+For the second group, the change would be subjected to quite a bit of scrutiny and iteration.
+The new API needs to be right (or at least easy to change later).
+The actual implementation doesn't matter that much.
+It's very important to minimize the amount of changed lines of code for changes of the second kind.
+Often, you start doing a change of the first kind, only to realise that you need to elevate to a change of the second kind.
+In this case, we'll probably ask you to split API changes into a separate PR.
+
+Changes of the third group should be pretty rare, so we don't specify any specific process for them.
+That said, adding an innocent-looking `pub use` is a very simple way to break encapsulation, keep an eye on it!
+
+Note: if you enjoyed this abstract hand-waving about boundaries, you might appreciate
+https://www.tedinski.com/2018/02/06/system-boundaries.html
+
+# Crates.io Dependencies
+
+We try to be very conservative with usage of crates.io dependencies.
+Don't use small "helper" crates (exception: `itertools` is allowed).
+If there's some general reusable bit of code you need, consider adding it to the `stdx` crate.
+
+# Minimal Tests
+
+Most tests in rust-analyzer start with a snippet of Rust code.
+This snippets should be minimal -- if you copy-paste a snippet of real code into the tests, make sure to remove everything which could be removed.
+There are many benefits to this:
+
+* less to read or to scroll past
+* easier to understand what exactly is tested
+* less stuff printed during printf-debugging
+* less time to run test
+
+It also makes sense to format snippets more compactly (for example, by placing enum definitions like `enum E { Foo, Bar }` on a single line),
+as long as they are still readable.
+
+## Order of Imports
+
+We separate import groups with blank lines
+
+```rust
+mod x;
+mod y;
+
+// First std.
+use std::{ ... }
+
+// Second, external crates (both crates.io crates and other rust-analyzer crates).
+use crate_foo::{ ... }
+use crate_bar::{ ... }
+
+// Then current crate.
+use crate::{}
+
+// Finally, parent and child modules, but prefer `use crate::`.
+use super::{}
+```
+
+Module declarations come before the imports.
+Order them in "suggested reading order" for a person new to the code base.
+
+## Import Style
+
+Items from `hir` and `ast` should be used qualified:
+
+```rust
+// Good
+use ra_syntax::ast;
+
+fn frobnicate(func: hir::Function, strukt: ast::StructDef) {}
+
+// Not as good
+use hir::Function;
+use ra_syntax::ast::StructDef;
+
+fn frobnicate(func: Function, strukt: StructDef) {}
+```
+
+Avoid local `use MyEnum::*` imports.
+
+Prefer `use crate::foo::bar` to `use super::bar`.
+
+## Order of Items
+
+Optimize for the reader who sees the file for the first time, and wants to get a general idea about what's going on.
+People read things from top to bottom, so place most important things first.
+
+Specifically, if all items except one are private, always put the non-private item on top.
+
+Put `struct`s and `enum`s first, functions and impls last.
+
+Do
+
+```rust
+// Good
+struct Foo {
+    bars: Vec<Bar>
+}
+
+struct Bar;
+```
+
+rather than
+
+```rust
+// Not as good
+struct Bar;
+
+struct Foo {
+    bars: Vec<Bar>
+}
+```
+
+## Variable Naming
+
+We generally use boring and long names for local variables ([yay code completion](https://github.com/rust-analyzer/rust-analyzer/pull/4162#discussion_r417130973)).
+The default name is a lowercased name of the type: `global_state: GlobalState`.
+Avoid ad-hoc acronyms and contractions, but use the ones that exist consistently (`db`, `ctx`, `acc`).
+The default name for "result of the function" local variable is `res`.
+The default name for "I don't really care about the name" variable is `it`.
+
+## Collection types
+
+We prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`.
+They use a hasher that's slightly faster and using them consistently will reduce code size by some small amount.
+
+## Preconditions
+
+Function preconditions should generally be expressed in types and provided by the caller (rather than checked by callee):
+
+```rust
+// Good
+fn frbonicate(walrus: Walrus) {
+    ...
+}
+
+// Not as good
+fn frobnicate(walrus: Option<Walrus>) {
+    let walrus = match walrus {
+        Some(it) => it,
+        None => return,
+    };
+    ...
+}
+```
+
+## Premature Pessimization
+
+Avoid writing code which is slower than it needs to be.
+Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly.
+
+```rust
+// Good
+use itertools::Itertools;
+
+let (first_word, second_word) = match text.split_ascii_whitespace().collect_tuple() {
+    Some(it) => it,
+    None => return,
+}
+
+// Not as good
+let words = text.split_ascii_whitespace().collect::<Vec<_>>();
+if words.len() != 2 {
+    return
+}
+```
+
+## Documentation
+
+For `.md` and `.adoc` files, prefer a sentence-per-line format, don't wrap lines.
+If the line is too long, you want to split the sentence in two :-)
+
+## Commit Style
+
+We don't have specific rules around git history hygiene.
+Maintaining clean git history is encouraged, but not enforced.
+We use rebase workflow, it's OK to rewrite history during PR review process.
+
+Avoid @mentioning people in commit messages and pull request descriptions(they are added to commit message by bors).
+Such messages create a lot of duplicate notification traffic during rebases.