| use clippy_utils::diagnostics::span_lint_and_help; |
| use clippy_utils::ty::{implements_trait, is_type_lang_item}; |
| use clippy_utils::{return_ty, trait_ref_of_method}; |
| use rustc_hir::{GenericParamKind, ImplItem, ImplItemKind, LangItem, Unsafety}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::sym; |
| use rustc_target::spec::abi::Abi; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for the definition of inherent methods with a signature of `to_string(&self) -> String`. |
| /// |
| /// ### Why is this bad? |
| /// This method is also implicitly defined if a type implements the `Display` trait. As the functionality of `Display` is much more versatile, it should be preferred. |
| /// |
| /// ### Example |
| /// ```rust |
| /// pub struct A; |
| /// |
| /// impl A { |
| /// pub fn to_string(&self) -> String { |
| /// "I am A".to_string() |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```rust |
| /// use std::fmt; |
| /// |
| /// pub struct A; |
| /// |
| /// impl fmt::Display for A { |
| /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| /// write!(f, "I am A") |
| /// } |
| /// } |
| /// ``` |
| #[clippy::version = "1.38.0"] |
| pub INHERENT_TO_STRING, |
| style, |
| "type implements inherent method `to_string()`, but should instead implement the `Display` trait" |
| } |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for the definition of inherent methods with a signature of `to_string(&self) -> String` and if the type implementing this method also implements the `Display` trait. |
| /// |
| /// ### Why is this bad? |
| /// This method is also implicitly defined if a type implements the `Display` trait. The less versatile inherent method will then shadow the implementation introduced by `Display`. |
| /// |
| /// ### Example |
| /// ```rust |
| /// use std::fmt; |
| /// |
| /// pub struct A; |
| /// |
| /// impl A { |
| /// pub fn to_string(&self) -> String { |
| /// "I am A".to_string() |
| /// } |
| /// } |
| /// |
| /// impl fmt::Display for A { |
| /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| /// write!(f, "I am A, too") |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```rust |
| /// use std::fmt; |
| /// |
| /// pub struct A; |
| /// |
| /// impl fmt::Display for A { |
| /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| /// write!(f, "I am A") |
| /// } |
| /// } |
| /// ``` |
| #[clippy::version = "1.38.0"] |
| pub INHERENT_TO_STRING_SHADOW_DISPLAY, |
| correctness, |
| "type implements inherent method `to_string()`, which gets shadowed by the implementation of the `Display` trait" |
| } |
| |
| declare_lint_pass!(InherentToString => [INHERENT_TO_STRING, INHERENT_TO_STRING_SHADOW_DISPLAY]); |
| |
| impl<'tcx> LateLintPass<'tcx> for InherentToString { |
| fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) { |
| if impl_item.span.from_expansion() { |
| return; |
| } |
| |
| // Check if item is a method called `to_string` and has a parameter 'self' |
| if let ImplItemKind::Fn(ref signature, _) = impl_item.kind |
| // #11201 |
| && let header = signature.header |
| && header.unsafety == Unsafety::Normal |
| && header.abi == Abi::Rust |
| && impl_item.ident.name == sym::to_string |
| && let decl = signature.decl |
| && decl.implicit_self.has_implicit_self() |
| && decl.inputs.len() == 1 |
| && impl_item.generics.params.iter().all(|p| matches!(p.kind, GenericParamKind::Lifetime { .. })) |
| // Check if return type is String |
| && is_type_lang_item(cx, return_ty(cx, impl_item.owner_id), LangItem::String) |
| // Filters instances of to_string which are required by a trait |
| && trait_ref_of_method(cx, impl_item.owner_id.def_id).is_none() |
| { |
| show_lint(cx, impl_item); |
| } |
| } |
| } |
| |
| fn show_lint(cx: &LateContext<'_>, item: &ImplItem<'_>) { |
| let display_trait_id = cx |
| .tcx |
| .get_diagnostic_item(sym::Display) |
| .expect("Failed to get trait ID of `Display`!"); |
| |
| // Get the real type of 'self' |
| let self_type = cx.tcx.fn_sig(item.owner_id).skip_binder().input(0); |
| let self_type = self_type.skip_binder().peel_refs(); |
| |
| // Emit either a warning or an error |
| if implements_trait(cx, self_type, display_trait_id, &[]) { |
| span_lint_and_help( |
| cx, |
| INHERENT_TO_STRING_SHADOW_DISPLAY, |
| item.span, |
| &format!( |
| "type `{self_type}` implements inherent method `to_string(&self) -> String` which shadows the implementation of `Display`" |
| ), |
| None, |
| &format!("remove the inherent method from type `{self_type}`"), |
| ); |
| } else { |
| span_lint_and_help( |
| cx, |
| INHERENT_TO_STRING, |
| item.span, |
| &format!("implementation of inherent method `to_string(&self) -> String` for type `{self_type}`"), |
| None, |
| &format!("implement trait `Display` for type `{self_type}` instead"), |
| ); |
| } |
| } |