mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
157 lines
5.1 KiB
Rust
157 lines
5.1 KiB
Rust
use if_chain::if_chain;
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use rustc_hir::{ImplItem, ImplItemKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::sym;
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use crate::utils::{
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get_trait_def_id, implements_trait, is_type_diagnostic_item, paths, return_ty, span_lint_and_help,
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trait_ref_of_method,
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};
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declare_clippy_lint! {
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/// **What it does:** Checks for the definition of inherent methods with a signature of `to_string(&self) -> String`.
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///
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/// **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.
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///
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/// **Known problems:** None
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///
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/// ** Example:**
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///
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/// ```rust
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/// // Bad
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/// pub struct A;
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///
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/// impl A {
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/// pub fn to_string(&self) -> String {
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/// "I am A".to_string()
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/// }
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/// }
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/// ```
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///
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/// ```rust
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/// // Good
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/// use std::fmt;
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///
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/// pub struct A;
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///
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/// impl fmt::Display for A {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f, "I am A")
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/// }
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/// }
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/// ```
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pub INHERENT_TO_STRING,
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style,
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"type implements inherent method `to_string()`, but should instead implement the `Display` trait"
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}
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declare_clippy_lint! {
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/// **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.
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///
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/// **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`.
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///
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/// **Known problems:** None
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///
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/// ** Example:**
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///
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/// ```rust
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/// // Bad
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/// use std::fmt;
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///
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/// pub struct A;
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///
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/// impl A {
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/// pub fn to_string(&self) -> String {
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/// "I am A".to_string()
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/// }
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/// }
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///
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/// impl fmt::Display for A {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f, "I am A, too")
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/// }
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/// }
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/// ```
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///
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/// ```rust
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/// // Good
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/// use std::fmt;
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///
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/// pub struct A;
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///
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/// impl fmt::Display for A {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f, "I am A")
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/// }
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/// }
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/// ```
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pub INHERENT_TO_STRING_SHADOW_DISPLAY,
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correctness,
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"type implements inherent method `to_string()`, which gets shadowed by the implementation of the `Display` trait"
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}
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declare_lint_pass!(InherentToString => [INHERENT_TO_STRING, INHERENT_TO_STRING_SHADOW_DISPLAY]);
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impl<'tcx> LateLintPass<'tcx> for InherentToString {
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fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) {
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if impl_item.span.from_expansion() {
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return;
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}
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if_chain! {
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// Check if item is a method, called to_string and has a parameter 'self'
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if let ImplItemKind::Fn(ref signature, _) = impl_item.kind;
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if impl_item.ident.name.as_str() == "to_string";
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let decl = &signature.decl;
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if decl.implicit_self.has_implicit_self();
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if decl.inputs.len() == 1;
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if impl_item.generics.params.is_empty();
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// Check if return type is String
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if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id()), sym::string_type);
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// Filters instances of to_string which are required by a trait
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if trait_ref_of_method(cx, impl_item.hir_id()).is_none();
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then {
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show_lint(cx, impl_item);
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}
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}
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}
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}
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fn show_lint(cx: &LateContext<'_>, item: &ImplItem<'_>) {
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let display_trait_id = get_trait_def_id(cx, &paths::DISPLAY_TRAIT).expect("Failed to get trait ID of `Display`!");
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// Get the real type of 'self'
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let self_type = cx.tcx.fn_sig(item.def_id).input(0);
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let self_type = self_type.skip_binder().peel_refs();
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// Emit either a warning or an error
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if implements_trait(cx, self_type, display_trait_id, &[]) {
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span_lint_and_help(
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cx,
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INHERENT_TO_STRING_SHADOW_DISPLAY,
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item.span,
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&format!(
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"type `{}` implements inherent method `to_string(&self) -> String` which shadows the implementation of `Display`",
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self_type.to_string()
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),
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None,
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&format!("remove the inherent method from type `{}`", self_type.to_string())
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);
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} else {
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span_lint_and_help(
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cx,
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INHERENT_TO_STRING,
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item.span,
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&format!(
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"implementation of inherent method `to_string(&self) -> String` for type `{}`",
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self_type.to_string()
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),
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None,
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&format!("implement trait `Display` for type `{}` instead", self_type.to_string()),
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);
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}
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}
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