| use crate::utils::paths; |
| use crate::utils::sugg::DiagnosticBuilderExt; |
| use crate::utils::{get_trait_def_id, implements_trait, return_ty, same_tys, span_lint_hir_and_then}; |
| use if_chain::if_chain; |
| use rustc::hir; |
| use rustc::hir::def_id::DefId; |
| use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass}; |
| use rustc::ty::{self, Ty}; |
| use rustc::util::nodemap::NodeSet; |
| use rustc::{declare_tool_lint, lint_array}; |
| use rustc_errors::Applicability; |
| use syntax::source_map::Span; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for types with a `fn new() -> Self` method and no |
| /// implementation of |
| /// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html). |
| /// |
| /// It detects both the case when a manual |
| /// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) |
| /// implementation is required and also when it can be created with |
| /// `#[derive(Default)]` |
| /// |
| /// **Why is this bad?** The user might expect to be able to use |
| /// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) as the |
| /// type can be constructed without arguments. |
| /// |
| /// **Known problems:** Hopefully none. |
| /// |
| /// **Example:** |
| /// |
| /// ```ignore |
| /// struct Foo(Bar); |
| /// |
| /// impl Foo { |
| /// fn new() -> Self { |
| /// Foo(Bar::new()) |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// Instead, use: |
| /// |
| /// ```ignore |
| /// struct Foo(Bar); |
| /// |
| /// impl Default for Foo { |
| /// fn default() -> Self { |
| /// Foo(Bar::new()) |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// Or, if |
| /// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) |
| /// can be derived by `#[derive(Default)]`: |
| /// |
| /// ```rust |
| /// struct Foo; |
| /// |
| /// impl Foo { |
| /// fn new() -> Self { |
| /// Foo |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// Instead, use: |
| /// |
| /// ```rust |
| /// #[derive(Default)] |
| /// struct Foo; |
| /// |
| /// impl Foo { |
| /// fn new() -> Self { |
| /// Foo |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// You can also have `new()` call `Default::default()`. |
| pub NEW_WITHOUT_DEFAULT, |
| style, |
| "`fn new() -> Self` method without `Default` implementation" |
| } |
| |
| #[derive(Clone, Default)] |
| pub struct NewWithoutDefault { |
| impling_types: Option<NodeSet>, |
| } |
| |
| impl LintPass for NewWithoutDefault { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(NEW_WITHOUT_DEFAULT) |
| } |
| |
| fn name(&self) -> &'static str { |
| "NewWithoutDefault" |
| } |
| } |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NewWithoutDefault { |
| fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) { |
| if let hir::ItemKind::Impl(_, _, _, _, None, _, ref items) = item.node { |
| for assoc_item in items { |
| if let hir::AssociatedItemKind::Method { has_self: false } = assoc_item.kind { |
| let impl_item = cx.tcx.hir().impl_item(assoc_item.id); |
| if in_external_macro(cx.sess(), impl_item.span) { |
| return; |
| } |
| if let hir::ImplItemKind::Method(ref sig, _) = impl_item.node { |
| let name = impl_item.ident.name; |
| let id = impl_item.hir_id; |
| if sig.header.constness == hir::Constness::Const { |
| // can't be implemented by default |
| return; |
| } |
| if sig.header.unsafety == hir::Unsafety::Unsafe { |
| // can't be implemented for unsafe new |
| return; |
| } |
| if impl_item.generics.params.iter().any(|gen| match gen.kind { |
| hir::GenericParamKind::Type { .. } => true, |
| _ => false, |
| }) { |
| // when the result of `new()` depends on a type parameter we should not require |
| // an |
| // impl of `Default` |
| return; |
| } |
| if sig.decl.inputs.is_empty() && name == "new" && cx.access_levels.is_reachable(id) { |
| let self_did = cx.tcx.hir().local_def_id_from_hir_id(cx.tcx.hir().get_parent_item(id)); |
| let self_ty = cx.tcx.type_of(self_did); |
| if_chain! { |
| if same_tys(cx, self_ty, return_ty(cx, id)); |
| if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT); |
| then { |
| if self.impling_types.is_none() { |
| let mut impls = NodeSet::default(); |
| cx.tcx.for_each_impl(default_trait_id, |d| { |
| if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() { |
| if let Some(node_id) = cx.tcx.hir().as_local_node_id(ty_def.did) { |
| impls.insert(node_id); |
| } |
| } |
| }); |
| self.impling_types = Some(impls); |
| } |
| |
| // Check if a Default implementation exists for the Self type, regardless of |
| // generics |
| if_chain! { |
| if let Some(ref impling_types) = self.impling_types; |
| if let Some(self_def) = cx.tcx.type_of(self_did).ty_adt_def(); |
| if self_def.did.is_local(); |
| then { |
| let self_id = cx.tcx.hir().local_def_id_to_node_id(self_def.did.to_local()); |
| if impling_types.contains(&self_id) { |
| return; |
| } |
| } |
| } |
| |
| if let Some(sp) = can_derive_default(self_ty, cx, default_trait_id) { |
| span_lint_hir_and_then( |
| cx, |
| NEW_WITHOUT_DEFAULT, |
| id, |
| impl_item.span, |
| &format!( |
| "you should consider deriving a `Default` implementation for `{}`", |
| self_ty |
| ), |
| |db| { |
| db.suggest_item_with_attr( |
| cx, |
| sp, |
| "try this", |
| "#[derive(Default)]", |
| Applicability::MaybeIncorrect, |
| ); |
| }); |
| } else { |
| span_lint_hir_and_then( |
| cx, |
| NEW_WITHOUT_DEFAULT, |
| id, |
| impl_item.span, |
| &format!( |
| "you should consider adding a `Default` implementation for `{}`", |
| self_ty |
| ), |
| |db| { |
| db.suggest_prepend_item( |
| cx, |
| item.span, |
| "try this", |
| &create_new_without_default_suggest_msg(self_ty), |
| Applicability::MaybeIncorrect, |
| ); |
| }, |
| ); |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| fn create_new_without_default_suggest_msg(ty: Ty<'_>) -> String { |
| #[rustfmt::skip] |
| format!( |
| "impl Default for {} {{ |
| fn default() -> Self {{ |
| Self::new() |
| }} |
| }}", ty) |
| } |
| |
| fn can_derive_default<'t, 'c>(ty: Ty<'t>, cx: &LateContext<'c, 't>, default_trait_id: DefId) -> Option<Span> { |
| match ty.sty { |
| ty::Adt(adt_def, substs) if adt_def.is_struct() => { |
| for field in adt_def.all_fields() { |
| let f_ty = field.ty(cx.tcx, substs); |
| if !implements_trait(cx, f_ty, default_trait_id, &[]) { |
| return None; |
| } |
| } |
| Some(cx.tcx.def_span(adt_def.did)) |
| }, |
| _ => None, |
| } |
| } |