src/tools/clippy/clippy_lints/src/self_named_constructors.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use clippy_utils::return_ty;
   3 use clippy_utils::ty::{contains_adt_constructor, contains_ty};
   4 use rustc_hir::{Impl, ImplItem, ImplItemKind, ItemKind, Node};
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_session::{declare_lint_pass, declare_tool_lint};
   7
   8 declare_clippy_lint! {
   9     /// ### What it does
  10     /// Warns when constructors have the same name as their types.
  11     ///
  12     /// ### Why is this bad?
  13     /// Repeating the name of the type is redundant.
  14     ///
  15     /// ### Example
  16     /// ```rust,ignore
  17     /// struct Foo {}
  18     ///
  19     /// impl Foo {
  20     ///     pub fn foo() -> Foo {
  21     ///         Foo {}
  22     ///     }
  23     /// }
  24     /// ```
  25     /// Use instead:
  26     /// ```rust,ignore
  27     /// struct Foo {}
  28     ///
  29     /// impl Foo {
  30     ///     pub fn new() -> Foo {
  31     ///         Foo {}
  32     ///     }
  33     /// }
  34     /// ```
  35     #[clippy::version = "1.55.0"]
  36     pub SELF_NAMED_CONSTRUCTORS,
  37     style,
  38     "method should not have the same name as the type it is implemented for"
  39 }
  40
  41 declare_lint_pass!(SelfNamedConstructors => [SELF_NAMED_CONSTRUCTORS]);
  42
  43 impl<'tcx> LateLintPass<'tcx> for SelfNamedConstructors {
  44     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) {
  45         match impl_item.kind {
  46             ImplItemKind::Fn(ref sig, _) => {
  47                 if sig.decl.implicit_self.has_implicit_self() {
  48                     return;
  49                 }
  50             },
  51             _ => return,
  52         }
  53
  54         let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
  55         let item = cx.tcx.hir().expect_item(parent);
  56         let self_ty = cx.tcx.type_of(item.def_id);
  57         let ret_ty = return_ty(cx, impl_item.hir_id());
  58
  59         // Do not check trait impls
  60         if matches!(item.kind, ItemKind::Impl(Impl { of_trait: Some(_), .. })) {
  61             return;
  62         }
  63
  64         // Ensure method is constructor-like
  65         if let Some(self_adt) = self_ty.ty_adt_def() {
  66             if !contains_adt_constructor(ret_ty, self_adt) {
  67                 return;
  68             }
  69         } else if !contains_ty(ret_ty, self_ty) {
  70             return;
  71         }
  72
  73         if_chain! {
  74             if let Some(self_def) = self_ty.ty_adt_def();
  75             if let Some(self_local_did) = self_def.did().as_local();
  76             let self_id = cx.tcx.hir().local_def_id_to_hir_id(self_local_did);
  77             if let Some(Node::Item(x)) = cx.tcx.hir().find(self_id);
  78             let type_name = x.ident.name.as_str().to_lowercase();
  79             if impl_item.ident.name.as_str() == type_name || impl_item.ident.name.as_str().replace('_', "") == type_name;
  80
  81             then {
  82                 span_lint(
  83                     cx,
  84                     SELF_NAMED_CONSTRUCTORS,
  85                     impl_item.span,
  86                     &format!("constructor `{}` has the same name as the type", impl_item.ident.name),
  87                 );
  88             }
  89         }
  90     }
  91 }