mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-11 05:42:47 +00:00
314 lines
11 KiB
Rust
314 lines
11 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::is_from_proc_macro;
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use clippy_utils::msrvs::{self, Msrv};
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use clippy_utils::ty::same_type_and_consts;
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use if_chain::if_chain;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_errors::Applicability;
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use rustc_hir::{
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self as hir,
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def::{CtorOf, DefKind, Res},
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def_id::LocalDefId,
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intravisit::{walk_inf, walk_ty, Visitor},
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Expr, ExprKind, FnRetTy, FnSig, GenericArg, HirId, Impl, ImplItemKind, Item, ItemKind, Pat, PatKind, Path, QPath,
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TyKind,
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};
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use rustc_hir_analysis::hir_ty_to_ty;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::Span;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for unnecessary repetition of structure name when a
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/// replacement with `Self` is applicable.
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///
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/// ### Why is this bad?
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/// Unnecessary repetition. Mixed use of `Self` and struct
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/// name
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/// feels inconsistent.
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///
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/// ### Known problems
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/// - Unaddressed false negative in fn bodies of trait implementations
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///
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/// ### Example
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/// ```rust
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/// struct Foo;
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/// impl Foo {
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/// fn new() -> Foo {
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/// Foo {}
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/// }
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/// }
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/// ```
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/// could be
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/// ```rust
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/// struct Foo;
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/// impl Foo {
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/// fn new() -> Self {
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/// Self {}
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/// }
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub USE_SELF,
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nursery,
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"unnecessary structure name repetition whereas `Self` is applicable"
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}
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#[derive(Default)]
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pub struct UseSelf {
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msrv: Msrv,
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stack: Vec<StackItem>,
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}
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impl UseSelf {
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#[must_use]
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pub fn new(msrv: Msrv) -> Self {
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Self {
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msrv,
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..Self::default()
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}
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}
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}
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#[derive(Debug)]
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enum StackItem {
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Check {
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impl_id: LocalDefId,
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in_body: u32,
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types_to_skip: FxHashSet<HirId>,
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},
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NoCheck,
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}
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impl_lint_pass!(UseSelf => [USE_SELF]);
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const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
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impl<'tcx> LateLintPass<'tcx> for UseSelf {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &Item<'tcx>) {
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if matches!(item.kind, ItemKind::OpaqueTy(_)) {
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// skip over `ItemKind::OpaqueTy` in order to lint `foo() -> impl <..>`
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return;
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}
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// We push the self types of `impl`s on a stack here. Only the top type on the stack is
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// relevant for linting, since this is the self type of the `impl` we're currently in. To
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// avoid linting on nested items, we push `StackItem::NoCheck` on the stack to signal, that
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// we're in an `impl` or nested item, that we don't want to lint
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let stack_item = if_chain! {
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if let ItemKind::Impl(Impl { self_ty, .. }) = item.kind;
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if let TyKind::Path(QPath::Resolved(_, item_path)) = self_ty.kind;
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let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
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if parameters.as_ref().map_or(true, |params| {
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!params.parenthesized && !params.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)))
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});
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if !item.span.from_expansion();
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if !is_from_proc_macro(cx, item); // expensive, should be last check
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then {
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StackItem::Check {
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impl_id: item.owner_id.def_id,
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in_body: 0,
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types_to_skip: std::iter::once(self_ty.hir_id).collect(),
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}
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} else {
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StackItem::NoCheck
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}
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};
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self.stack.push(stack_item);
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}
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fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
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if !matches!(item.kind, ItemKind::OpaqueTy(_)) {
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self.stack.pop();
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}
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}
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fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
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// We want to skip types in trait `impl`s that aren't declared as `Self` in the trait
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// declaration. The collection of those types is all this method implementation does.
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if_chain! {
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if let ImplItemKind::Fn(FnSig { decl, .. }, ..) = impl_item.kind;
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if let Some(&mut StackItem::Check {
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impl_id,
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ref mut types_to_skip,
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..
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}) = self.stack.last_mut();
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if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_id);
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then {
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// `self_ty` is the semantic self type of `impl <trait> for <type>`. This cannot be
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// `Self`.
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let self_ty = impl_trait_ref.self_ty();
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// `trait_method_sig` is the signature of the function, how it is declared in the
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// trait, not in the impl of the trait.
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let trait_method = cx
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.tcx
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.associated_item(impl_item.owner_id)
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.trait_item_def_id
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.expect("impl method matches a trait method");
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let trait_method_sig = cx.tcx.fn_sig(trait_method);
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let trait_method_sig = cx.tcx.erase_late_bound_regions(trait_method_sig);
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// `impl_inputs_outputs` is an iterator over the types (`hir::Ty`) declared in the
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// implementation of the trait.
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let output_hir_ty = if let FnRetTy::Return(ty) = &decl.output {
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Some(&**ty)
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} else {
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None
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};
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let impl_inputs_outputs = decl.inputs.iter().chain(output_hir_ty);
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// `impl_hir_ty` (of type `hir::Ty`) represents the type written in the signature.
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//
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// `trait_sem_ty` (of type `ty::Ty`) is the semantic type for the signature in the
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// trait declaration. This is used to check if `Self` was used in the trait
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// declaration.
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//
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// If `any`where in the `trait_sem_ty` the `self_ty` was used verbatim (as opposed
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// to `Self`), we want to skip linting that type and all subtypes of it. This
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// avoids suggestions to e.g. replace `Vec<u8>` with `Vec<Self>`, in an `impl Trait
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// for u8`, when the trait always uses `Vec<u8>`.
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//
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// See also https://github.com/rust-lang/rust-clippy/issues/2894.
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for (impl_hir_ty, trait_sem_ty) in impl_inputs_outputs.zip(trait_method_sig.inputs_and_output) {
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if trait_sem_ty.walk().any(|inner| inner == self_ty.into()) {
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let mut visitor = SkipTyCollector::default();
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visitor.visit_ty(impl_hir_ty);
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types_to_skip.extend(visitor.types_to_skip);
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}
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}
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}
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}
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}
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fn check_body(&mut self, _: &LateContext<'_>, _: &hir::Body<'_>) {
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// `hir_ty_to_ty` cannot be called in `Body`s or it will panic (sometimes). But in bodies
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// we can use `cx.typeck_results.node_type(..)` to get the `ty::Ty` from a `hir::Ty`.
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// However the `node_type()` method can *only* be called in bodies.
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if let Some(&mut StackItem::Check { ref mut in_body, .. }) = self.stack.last_mut() {
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*in_body = in_body.saturating_add(1);
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}
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}
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fn check_body_post(&mut self, _: &LateContext<'_>, _: &hir::Body<'_>) {
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if let Some(&mut StackItem::Check { ref mut in_body, .. }) = self.stack.last_mut() {
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*in_body = in_body.saturating_sub(1);
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}
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}
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fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
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if_chain! {
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if !hir_ty.span.from_expansion();
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if self.msrv.meets(msrvs::TYPE_ALIAS_ENUM_VARIANTS);
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if let Some(&StackItem::Check {
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impl_id,
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in_body,
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ref types_to_skip,
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}) = self.stack.last();
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if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind;
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if !matches!(
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path.res,
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Res::SelfTyParam { .. }
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| Res::SelfTyAlias { .. }
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| Res::Def(DefKind::TyParam, _)
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);
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if !types_to_skip.contains(&hir_ty.hir_id);
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let ty = if in_body > 0 {
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cx.typeck_results().node_type(hir_ty.hir_id)
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} else {
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hir_ty_to_ty(cx.tcx, hir_ty)
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};
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if same_type_and_consts(ty, cx.tcx.type_of(impl_id));
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then {
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span_lint(cx, hir_ty.span);
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}
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}
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}
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
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if_chain! {
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if !expr.span.from_expansion();
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if self.msrv.meets(msrvs::TYPE_ALIAS_ENUM_VARIANTS);
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if let Some(&StackItem::Check { impl_id, .. }) = self.stack.last();
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if cx.typeck_results().expr_ty(expr) == cx.tcx.type_of(impl_id);
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then {} else { return; }
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}
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match expr.kind {
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ExprKind::Struct(QPath::Resolved(_, path), ..) => check_path(cx, path),
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ExprKind::Call(fun, _) => {
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if let ExprKind::Path(QPath::Resolved(_, path)) = fun.kind {
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check_path(cx, path);
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}
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},
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ExprKind::Path(QPath::Resolved(_, path)) => check_path(cx, path),
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_ => (),
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}
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}
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fn check_pat(&mut self, cx: &LateContext<'_>, pat: &Pat<'_>) {
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if_chain! {
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if !pat.span.from_expansion();
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if self.msrv.meets(msrvs::TYPE_ALIAS_ENUM_VARIANTS);
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if let Some(&StackItem::Check { impl_id, .. }) = self.stack.last();
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// get the path from the pattern
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if let PatKind::Path(QPath::Resolved(_, path))
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| PatKind::TupleStruct(QPath::Resolved(_, path), _, _)
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| PatKind::Struct(QPath::Resolved(_, path), _, _) = pat.kind;
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if cx.typeck_results().pat_ty(pat) == cx.tcx.type_of(impl_id);
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then {
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check_path(cx, path);
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}
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}
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}
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extract_msrv_attr!(LateContext);
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}
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#[derive(Default)]
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struct SkipTyCollector {
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types_to_skip: Vec<HirId>,
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}
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impl<'tcx> Visitor<'tcx> for SkipTyCollector {
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fn visit_infer(&mut self, inf: &hir::InferArg) {
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self.types_to_skip.push(inf.hir_id);
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walk_inf(self, inf);
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}
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fn visit_ty(&mut self, hir_ty: &hir::Ty<'_>) {
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self.types_to_skip.push(hir_ty.hir_id);
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walk_ty(self, hir_ty);
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}
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}
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fn span_lint(cx: &LateContext<'_>, span: Span) {
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span_lint_and_sugg(
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cx,
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USE_SELF,
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span,
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"unnecessary structure name repetition",
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"use the applicable keyword",
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"Self".to_owned(),
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Applicability::MachineApplicable,
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);
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}
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fn check_path(cx: &LateContext<'_>, path: &Path<'_>) {
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match path.res {
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Res::Def(DefKind::Ctor(CtorOf::Variant, _) | DefKind::Variant, ..) => {
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lint_path_to_variant(cx, path);
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},
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Res::Def(DefKind::Ctor(CtorOf::Struct, _) | DefKind::Struct, ..) => span_lint(cx, path.span),
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_ => (),
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}
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}
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fn lint_path_to_variant(cx: &LateContext<'_>, path: &Path<'_>) {
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if let [.., self_seg, _variant] = path.segments {
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let span = path
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.span
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.with_hi(self_seg.args().span_ext().unwrap_or(self_seg.ident.span).hi());
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span_lint(cx, span);
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}
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}
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