From 9e4a2d7fcab0a32a8137f52e4b3a1442604ba61c Mon Sep 17 00:00:00 2001 From: blyxyas Date: Mon, 17 Apr 2023 23:08:44 +0200 Subject: [PATCH] Fixes based on reviews --- book/src/development/method_checking.md | 47 +++++++++++++------------ 1 file changed, 24 insertions(+), 23 deletions(-) diff --git a/book/src/development/method_checking.md b/book/src/development/method_checking.md index 604fcf193df..c93af6f21d2 100644 --- a/book/src/development/method_checking.md +++ b/book/src/development/method_checking.md @@ -4,56 +4,58 @@ In some scenarios we might want to check for methods when developing a lint. There are two kinds of questions that we might be curious about: - Invocation: Does an expression call a specific method? -- Definition: Does the type `Ty` of an expression define a method? +- Definition: Does an `impl` define a method? ## Checking if an `expr` is calling a specific method Suppose we have an `expr`, we can check whether it calls a specific method, e.g. `our_fancy_method`, by performing a pattern match on -the [ExprKind] that we can access from `expr.kind`: +the [`ExprKind`] that we can access from `expr.kind`: ```rust use rustc_hir as hir; use rustc_lint::{LateContext, LateLintPass}; use rustc_span::sym; +use clippy_utils::is_trait_method; impl<'tcx> LateLintPass<'tcx> for OurFancyMethodLint { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { // Check our expr is calling a method with pattern matching - if let hir::ExprKind::MethodCall(path, _, [_self_arg, ..]) = &expr.kind + if let hir::ExprKind::MethodCall(path, _, [self_arg, ..]) = &expr.kind // Check if the name of this method is `our_fancy_method` && path.ident.name == sym!(our_fancy_method) // We can check the type of the self argument whenever necessary. - // (It's necessary if we want to check that method is specifically belonging to a specific trait, - // for example, a `map` method could belong to user-defined trait instead of to `Iterator`) - // See the "Type Checking" chapter of the Clippy book for more information. + // (It's necessary if we want to check that method is specifically belonging to a specific trait, + // for example, a `map` method could belong to user-defined trait instead of to `Iterator`) + // See the next section for more information. + && is_trait_method(cx, self_arg, sym::OurFancyTrait) { - println!("`expr` is a method call for `our_fancy_method`"); + println!("`expr` is a method call for `our_fancy_method`"); } } } ``` -Take a closer look at the `ExprKind` enum variant [MethodCall] for more +Take a closer look at the `ExprKind` enum variant [`MethodCall`] for more information on the pattern matching. As mentioned in [Define Lints](define_lints.md#lint-types), the `methods` lint type is full of pattern matching with `Methodcall` in case the reader wishes to explore more. Additionally, we use the [`clippy_utils::sym!`][sym] macro to conveniently convert -an input `our_fancy_method` into a `Symbol` and compare that symbol to the [ident][Ident]'s name in the [PathSegment] -in the [MethodCall]. +an input `our_fancy_method` into a `Symbol` and compare that symbol to the [`ident`][Ident]'s name in the [`PathSegment`] +in the [`MethodCall`]. -## Checking if a type defines a specific method +## Checking if a `impl` block implements a method While sometimes we want to check whether a method is being called or not, -other times we want to know if our type `Ty` defines a method. +other times we want to know if our `Ty` defines a method. -To check if our type defines a method called `our_fancy_method`, -we will utilize the [check_impl_item] method that is available -in our beloved [LateLintPass] (for more information, refer to the +To check if our `impl` block defines a method `our_fancy_method`, +we will utilize the [`check_impl_item`] method that is available +in our beloved [`LateLintPass`] (for more information, refer to the ["Lint Passes"](lint_passes.md) chapter in Clippy book). -This method provides us with an [ImplItem] struct, which represents +This method provides us with an [`ImplItem`] struct, which represents anything within an `impl` block. Let us take a look at how we might check for the implementation of @@ -65,7 +67,6 @@ use clippy_utils::return_ty; use rustc_hir::{ImplItem, ImplItemKind}; use rustc_lint::{LateContext, LateLintPass}; use rustc_span::symbol::sym; - impl<'tcx> LateLintPass<'tcx> for MyTypeImpl { fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) { // Check if item is a method/function @@ -83,11 +84,11 @@ impl<'tcx> LateLintPass<'tcx> for MyTypeImpl { } ``` -[check_impl_item]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_lint/trait.LateLintPass.html#method.check_impl_item -[ExprKind]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/enum.ExprKind.html +[`check_impl_item`]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_lint/trait.LateLintPass.html#method.check_impl_item +[`ExprKind`]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/enum.ExprKind.html [Ident]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_span/symbol/struct.Ident.html -[ImplItem]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_hir/hir/struct.ImplItem.html -[LateLintPass]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_lint/trait.LateLintPass.html -[MethodCall]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/enum.ExprKind.html#variant.MethodCall -[PathSegment]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/struct.PathSegment.html +[`ImplItem`]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_hir/hir/struct.ImplItem.html +[`LateLintPass`]: https://doc.rust-lang.org/stable/nightly-rustc/rustc_lint/trait.LateLintPass.html +[`MethodCall`]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/enum.ExprKind.html#variant.MethodCall +[`PathSegment`]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/hir/struct.PathSegment.html [sym]: https://doc.rust-lang.org/stable/nightly-rustc/clippy_utils/macro.sym.html