docs: update lint registration for statically-combined passes (#17178)

Follow up after #17124 and
#17132

changelog: none

Author: ada4a

CONTRIBUTING.md

@@ -124,8 +124,11 @@ To have `rust-analyzer` also work in the `clippy_dev` and `lintcheck` crates, ad
 
 ## How Clippy works
 
-[`clippy_lints/src/lib.rs`][lint_crate_entry] imports all the different lint modules and registers in the [`LintStore`].
-For example, the [`else_if_without_else`][else_if_without_else] lint is registered like this:
+[`clippy_lints/src/lib.rs`][lint_crate_entry] imports all the different lint modules and registers them in the
+[`LintStore`]. All early passes are folded into a single `CombinedEarlyLintPass`, and all late passes into a single
+`CombinedLateLintPass`, each registered once with the store. A pass is added to one of these by listing it in the
+`early_lint_methods!` or `late_lint_methods!` macro invocation. For example, the
+[`else_if_without_else`][else_if_without_else] lint is added like this:
 
 ```rust
 // ./clippy_lints/src/lib.rs
@@ -134,18 +137,21 @@ For example, the [`else_if_without_else`][else_if_without_else] lint is register
 pub mod else_if_without_else;
 // ...
 
-pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
-    // ...
-    store.register_early_pass(|| Box::new(else_if_without_else::ElseIfWithoutElse));
-    // ...
-}
+rustc_lint::early_lint_methods!(
+    crate::combined_early_lint_pass,
+    [CombinedEarlyLintPass, (/* ... */), [
+        // ...
+        ElseIfWithoutElse: else_if_without_else::ElseIfWithoutElse = else_if_without_else::ElseIfWithoutElse,
+        // ...
+    ]]
+);
 ```
 
-The [`rustc_lint::LintStore`][`LintStore`] provides two methods to register lints:
-[register_early_pass][reg_early_pass] and [register_late_pass][reg_late_pass]. Both take an object
-that implements an [`EarlyLintPass`][early_lint_pass] or [`LateLintPass`][late_lint_pass] respectively. This is done in
-every single lint. It's worth noting that the majority of `clippy_lints/src/lib.rs` is autogenerated by `cargo dev
-update_lints`. When you are writing your own lint, you can use that script to save you some time.
+Each entry has the form `Field: Type = constructor`, where the constructor builds the pass (passing `conf` when the pass
+needs the user configuration). The combined passes implement [`EarlyLintPass`][early_lint_pass] and
+[`LateLintPass`][late_lint_pass] respectively, so each listed pass must also implement the matching trait. It's worth
+noting that the majority of `clippy_lints/src/lib.rs` is autogenerated by `cargo dev update_lints`. When you are
+writing your own lint, you can use that script to save you some time.
 
 ```rust
 // ./clippy_lints/src/else_if_without_else.rs
@@ -167,14 +173,12 @@ The difference between `EarlyLintPass` and `LateLintPass` is that the methods of
 AST information. The methods of the `LateLintPass` trait are executed after type checking and contain type information
 via the `LateContext` parameter.
 
-That's why the `else_if_without_else` example uses the `register_early_pass` function. Because the
+That's why the `else_if_without_else` example is listed in `early_lint_methods!`. Because the
 [actual lint logic][else_if_without_else] does not depend on any type information.
 
 [lint_crate_entry]: https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/lib.rs
 [else_if_without_else]: https://github.com/rust-lang/rust-clippy/blob/4253aa7137cb7378acc96133c787e49a345c2b3c/clippy_lints/src/else_if_without_else.rs
 [`LintStore`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html
-[reg_early_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html#method.register_early_pass
-[reg_late_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html#method.register_late_pass
 [early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
 [late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.LateLintPass.html
 

book/src/development/adding_lints.md

@@ -282,21 +282,22 @@ When using `cargo dev new_lint`, the lint is automatically registered and
 nothing more has to be done.
 
 When declaring a new lint by hand and `cargo dev update_lints` is used, the lint
-pass may have to be registered manually in the `register_lints` function in
-`clippy_lints/src/lib.rs`:
+pass may have to be registered manually by adding an entry to the
+`early_lint_methods!` macro invocation in `clippy_lints/src/lib.rs`, at the
+`// add early passes here` marker:
 
 ```rust,ignore
-store.register_early_pass(|| Box::new(foo_functions::FooFunctions));
+FooFunctions: foo_functions::FooFunctions = foo_functions::FooFunctions,
 ```
 
-As one may expect, there is a corresponding `register_late_pass` method
-available as well. Without a call to one of `register_early_pass` or
-`register_late_pass`, the lint pass in question will not be run.
+As one may expect, there is a corresponding `late_lint_methods!` macro available
+as well. Without an entry in one of `early_lint_methods!` or `late_lint_methods!`,
+the lint pass in question will not be run.
 
 One reason that `cargo dev update_lints` does not automate this step is that
 multiple lints can use the same lint pass, so registering the lint pass may
 already be done when adding a new lint. Another reason that this step is not
-automated is that the order that the passes are registered determines the order
+automated is that the order that the passes are listed determines the order
 the passes actually run, which in turn affects the order that any emitted lints
 are output in.
 

book/src/development/defining_lints.md

@@ -184,18 +184,19 @@ However, sometimes we might want to declare a new lint by hand. In this case,
 we'd use `cargo dev update_lints` command afterwards.
 
 When a lint is manually declared, we might need to register the lint pass
-manually in the `register_lints` function in `clippy_lints/src/lib.rs`:
+manually by adding an entry to the `late_lint_methods!` macro invocation in
+`clippy_lints/src/lib.rs`, at the `// add late passes here` marker:
 
 ```rust
-store.register_late_pass(|_| Box::new(foo_functions::FooFunctions));
+FooFunctions: foo_functions::FooFunctions = foo_functions::FooFunctions,
 ```
 
 As you might have guessed, where there's something late, there is something
-early: in Clippy there is a `register_early_pass` method as well. More on early
+early: in Clippy there is an `early_lint_methods!` macro as well. More on early
 vs. late passes in the [Lint Passes] chapter.
 
-Without a call to one of `register_early_pass` or `register_late_pass`, the lint
-pass in question will not be run.
+Without an entry in one of `early_lint_methods!` or `late_lint_methods!`, the
+lint pass in question will not be run.
 
 
 [all_lints]: https://rust-lang.github.io/rust-clippy/master/